mm: fix overflow check in expand_upwards()
[muen/linux.git] / mm / mmap.c
1 /*
2  * mm/mmap.c
3  *
4  * Written by obz.
5  *
6  * Address space accounting code        <alan@lxorguk.ukuu.org.uk>
7  */
8
9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
11 #include <linux/kernel.h>
12 #include <linux/slab.h>
13 #include <linux/backing-dev.h>
14 #include <linux/mm.h>
15 #include <linux/vmacache.h>
16 #include <linux/shm.h>
17 #include <linux/mman.h>
18 #include <linux/pagemap.h>
19 #include <linux/swap.h>
20 #include <linux/syscalls.h>
21 #include <linux/capability.h>
22 #include <linux/init.h>
23 #include <linux/file.h>
24 #include <linux/fs.h>
25 #include <linux/personality.h>
26 #include <linux/security.h>
27 #include <linux/hugetlb.h>
28 #include <linux/shmem_fs.h>
29 #include <linux/profile.h>
30 #include <linux/export.h>
31 #include <linux/mount.h>
32 #include <linux/mempolicy.h>
33 #include <linux/rmap.h>
34 #include <linux/mmu_notifier.h>
35 #include <linux/mmdebug.h>
36 #include <linux/perf_event.h>
37 #include <linux/audit.h>
38 #include <linux/khugepaged.h>
39 #include <linux/uprobes.h>
40 #include <linux/rbtree_augmented.h>
41 #include <linux/notifier.h>
42 #include <linux/memory.h>
43 #include <linux/printk.h>
44 #include <linux/userfaultfd_k.h>
45 #include <linux/moduleparam.h>
46 #include <linux/pkeys.h>
47
48 #include <linux/uaccess.h>
49 #include <asm/cacheflush.h>
50 #include <asm/tlb.h>
51 #include <asm/mmu_context.h>
52
53 #include "internal.h"
54
55 #ifndef arch_mmap_check
56 #define arch_mmap_check(addr, len, flags)       (0)
57 #endif
58
59 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
60 const int mmap_rnd_bits_min = CONFIG_ARCH_MMAP_RND_BITS_MIN;
61 const int mmap_rnd_bits_max = CONFIG_ARCH_MMAP_RND_BITS_MAX;
62 int mmap_rnd_bits __read_mostly = CONFIG_ARCH_MMAP_RND_BITS;
63 #endif
64 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS
65 const int mmap_rnd_compat_bits_min = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MIN;
66 const int mmap_rnd_compat_bits_max = CONFIG_ARCH_MMAP_RND_COMPAT_BITS_MAX;
67 int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
68 #endif
69
70 static bool ignore_rlimit_data;
71 core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
72
73 static void unmap_region(struct mm_struct *mm,
74                 struct vm_area_struct *vma, struct vm_area_struct *prev,
75                 unsigned long start, unsigned long end);
76
77 /* description of effects of mapping type and prot in current implementation.
78  * this is due to the limited x86 page protection hardware.  The expected
79  * behavior is in parens:
80  *
81  * map_type     prot
82  *              PROT_NONE       PROT_READ       PROT_WRITE      PROT_EXEC
83  * MAP_SHARED   r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
84  *              w: (no) no      w: (no) no      w: (yes) yes    w: (no) no
85  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
86  *
87  * MAP_PRIVATE  r: (no) no      r: (yes) yes    r: (no) yes     r: (no) yes
88  *              w: (no) no      w: (no) no      w: (copy) copy  w: (no) no
89  *              x: (no) no      x: (no) yes     x: (no) yes     x: (yes) yes
90  *
91  * On arm64, PROT_EXEC has the following behaviour for both MAP_SHARED and
92  * MAP_PRIVATE:
93  *                                                              r: (no) no
94  *                                                              w: (no) no
95  *                                                              x: (yes) yes
96  */
97 pgprot_t protection_map[16] __ro_after_init = {
98         __P000, __P001, __P010, __P011, __P100, __P101, __P110, __P111,
99         __S000, __S001, __S010, __S011, __S100, __S101, __S110, __S111
100 };
101
102 pgprot_t vm_get_page_prot(unsigned long vm_flags)
103 {
104         return __pgprot(pgprot_val(protection_map[vm_flags &
105                                 (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
106                         pgprot_val(arch_vm_get_page_prot(vm_flags)));
107 }
108 EXPORT_SYMBOL(vm_get_page_prot);
109
110 static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
111 {
112         return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
113 }
114
115 /* Update vma->vm_page_prot to reflect vma->vm_flags. */
116 void vma_set_page_prot(struct vm_area_struct *vma)
117 {
118         unsigned long vm_flags = vma->vm_flags;
119         pgprot_t vm_page_prot;
120
121         vm_page_prot = vm_pgprot_modify(vma->vm_page_prot, vm_flags);
122         if (vma_wants_writenotify(vma, vm_page_prot)) {
123                 vm_flags &= ~VM_SHARED;
124                 vm_page_prot = vm_pgprot_modify(vm_page_prot, vm_flags);
125         }
126         /* remove_protection_ptes reads vma->vm_page_prot without mmap_sem */
127         WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
128 }
129
130 /*
131  * Requires inode->i_mapping->i_mmap_rwsem
132  */
133 static void __remove_shared_vm_struct(struct vm_area_struct *vma,
134                 struct file *file, struct address_space *mapping)
135 {
136         if (vma->vm_flags & VM_DENYWRITE)
137                 atomic_inc(&file_inode(file)->i_writecount);
138         if (vma->vm_flags & VM_SHARED)
139                 mapping_unmap_writable(mapping);
140
141         flush_dcache_mmap_lock(mapping);
142         vma_interval_tree_remove(vma, &mapping->i_mmap);
143         flush_dcache_mmap_unlock(mapping);
144 }
145
146 /*
147  * Unlink a file-based vm structure from its interval tree, to hide
148  * vma from rmap and vmtruncate before freeing its page tables.
149  */
150 void unlink_file_vma(struct vm_area_struct *vma)
151 {
152         struct file *file = vma->vm_file;
153
154         if (file) {
155                 struct address_space *mapping = file->f_mapping;
156                 i_mmap_lock_write(mapping);
157                 __remove_shared_vm_struct(vma, file, mapping);
158                 i_mmap_unlock_write(mapping);
159         }
160 }
161
162 /*
163  * Close a vm structure and free it, returning the next.
164  */
165 static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
166 {
167         struct vm_area_struct *next = vma->vm_next;
168
169         might_sleep();
170         if (vma->vm_ops && vma->vm_ops->close)
171                 vma->vm_ops->close(vma);
172         if (vma->vm_file)
173                 fput(vma->vm_file);
174         mpol_put(vma_policy(vma));
175         kmem_cache_free(vm_area_cachep, vma);
176         return next;
177 }
178
179 static int do_brk(unsigned long addr, unsigned long len, struct list_head *uf);
180
181 SYSCALL_DEFINE1(brk, unsigned long, brk)
182 {
183         unsigned long retval;
184         unsigned long newbrk, oldbrk;
185         struct mm_struct *mm = current->mm;
186         struct vm_area_struct *next;
187         unsigned long min_brk;
188         bool populate;
189         LIST_HEAD(uf);
190
191         if (down_write_killable(&mm->mmap_sem))
192                 return -EINTR;
193
194 #ifdef CONFIG_COMPAT_BRK
195         /*
196          * CONFIG_COMPAT_BRK can still be overridden by setting
197          * randomize_va_space to 2, which will still cause mm->start_brk
198          * to be arbitrarily shifted
199          */
200         if (current->brk_randomized)
201                 min_brk = mm->start_brk;
202         else
203                 min_brk = mm->end_data;
204 #else
205         min_brk = mm->start_brk;
206 #endif
207         if (brk < min_brk)
208                 goto out;
209
210         /*
211          * Check against rlimit here. If this check is done later after the test
212          * of oldbrk with newbrk then it can escape the test and let the data
213          * segment grow beyond its set limit the in case where the limit is
214          * not page aligned -Ram Gupta
215          */
216         if (check_data_rlimit(rlimit(RLIMIT_DATA), brk, mm->start_brk,
217                               mm->end_data, mm->start_data))
218                 goto out;
219
220         newbrk = PAGE_ALIGN(brk);
221         oldbrk = PAGE_ALIGN(mm->brk);
222         if (oldbrk == newbrk)
223                 goto set_brk;
224
225         /* Always allow shrinking brk. */
226         if (brk <= mm->brk) {
227                 if (!do_munmap(mm, newbrk, oldbrk-newbrk, &uf))
228                         goto set_brk;
229                 goto out;
230         }
231
232         /* Check against existing mmap mappings. */
233         next = find_vma(mm, oldbrk);
234         if (next && newbrk + PAGE_SIZE > vm_start_gap(next))
235                 goto out;
236
237         /* Ok, looks good - let it rip. */
238         if (do_brk(oldbrk, newbrk-oldbrk, &uf) < 0)
239                 goto out;
240
241 set_brk:
242         mm->brk = brk;
243         populate = newbrk > oldbrk && (mm->def_flags & VM_LOCKED) != 0;
244         up_write(&mm->mmap_sem);
245         userfaultfd_unmap_complete(mm, &uf);
246         if (populate)
247                 mm_populate(oldbrk, newbrk - oldbrk);
248         return brk;
249
250 out:
251         retval = mm->brk;
252         up_write(&mm->mmap_sem);
253         return retval;
254 }
255
256 static long vma_compute_subtree_gap(struct vm_area_struct *vma)
257 {
258         unsigned long max, prev_end, subtree_gap;
259
260         /*
261          * Note: in the rare case of a VM_GROWSDOWN above a VM_GROWSUP, we
262          * allow two stack_guard_gaps between them here, and when choosing
263          * an unmapped area; whereas when expanding we only require one.
264          * That's a little inconsistent, but keeps the code here simpler.
265          */
266         max = vm_start_gap(vma);
267         if (vma->vm_prev) {
268                 prev_end = vm_end_gap(vma->vm_prev);
269                 if (max > prev_end)
270                         max -= prev_end;
271                 else
272                         max = 0;
273         }
274         if (vma->vm_rb.rb_left) {
275                 subtree_gap = rb_entry(vma->vm_rb.rb_left,
276                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
277                 if (subtree_gap > max)
278                         max = subtree_gap;
279         }
280         if (vma->vm_rb.rb_right) {
281                 subtree_gap = rb_entry(vma->vm_rb.rb_right,
282                                 struct vm_area_struct, vm_rb)->rb_subtree_gap;
283                 if (subtree_gap > max)
284                         max = subtree_gap;
285         }
286         return max;
287 }
288
289 #ifdef CONFIG_DEBUG_VM_RB
290 static int browse_rb(struct mm_struct *mm)
291 {
292         struct rb_root *root = &mm->mm_rb;
293         int i = 0, j, bug = 0;
294         struct rb_node *nd, *pn = NULL;
295         unsigned long prev = 0, pend = 0;
296
297         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
298                 struct vm_area_struct *vma;
299                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
300                 if (vma->vm_start < prev) {
301                         pr_emerg("vm_start %lx < prev %lx\n",
302                                   vma->vm_start, prev);
303                         bug = 1;
304                 }
305                 if (vma->vm_start < pend) {
306                         pr_emerg("vm_start %lx < pend %lx\n",
307                                   vma->vm_start, pend);
308                         bug = 1;
309                 }
310                 if (vma->vm_start > vma->vm_end) {
311                         pr_emerg("vm_start %lx > vm_end %lx\n",
312                                   vma->vm_start, vma->vm_end);
313                         bug = 1;
314                 }
315                 spin_lock(&mm->page_table_lock);
316                 if (vma->rb_subtree_gap != vma_compute_subtree_gap(vma)) {
317                         pr_emerg("free gap %lx, correct %lx\n",
318                                vma->rb_subtree_gap,
319                                vma_compute_subtree_gap(vma));
320                         bug = 1;
321                 }
322                 spin_unlock(&mm->page_table_lock);
323                 i++;
324                 pn = nd;
325                 prev = vma->vm_start;
326                 pend = vma->vm_end;
327         }
328         j = 0;
329         for (nd = pn; nd; nd = rb_prev(nd))
330                 j++;
331         if (i != j) {
332                 pr_emerg("backwards %d, forwards %d\n", j, i);
333                 bug = 1;
334         }
335         return bug ? -1 : i;
336 }
337
338 static void validate_mm_rb(struct rb_root *root, struct vm_area_struct *ignore)
339 {
340         struct rb_node *nd;
341
342         for (nd = rb_first(root); nd; nd = rb_next(nd)) {
343                 struct vm_area_struct *vma;
344                 vma = rb_entry(nd, struct vm_area_struct, vm_rb);
345                 VM_BUG_ON_VMA(vma != ignore &&
346                         vma->rb_subtree_gap != vma_compute_subtree_gap(vma),
347                         vma);
348         }
349 }
350
351 static void validate_mm(struct mm_struct *mm)
352 {
353         int bug = 0;
354         int i = 0;
355         unsigned long highest_address = 0;
356         struct vm_area_struct *vma = mm->mmap;
357
358         while (vma) {
359                 struct anon_vma *anon_vma = vma->anon_vma;
360                 struct anon_vma_chain *avc;
361
362                 if (anon_vma) {
363                         anon_vma_lock_read(anon_vma);
364                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
365                                 anon_vma_interval_tree_verify(avc);
366                         anon_vma_unlock_read(anon_vma);
367                 }
368
369                 highest_address = vm_end_gap(vma);
370                 vma = vma->vm_next;
371                 i++;
372         }
373         if (i != mm->map_count) {
374                 pr_emerg("map_count %d vm_next %d\n", mm->map_count, i);
375                 bug = 1;
376         }
377         if (highest_address != mm->highest_vm_end) {
378                 pr_emerg("mm->highest_vm_end %lx, found %lx\n",
379                           mm->highest_vm_end, highest_address);
380                 bug = 1;
381         }
382         i = browse_rb(mm);
383         if (i != mm->map_count) {
384                 if (i != -1)
385                         pr_emerg("map_count %d rb %d\n", mm->map_count, i);
386                 bug = 1;
387         }
388         VM_BUG_ON_MM(bug, mm);
389 }
390 #else
391 #define validate_mm_rb(root, ignore) do { } while (0)
392 #define validate_mm(mm) do { } while (0)
393 #endif
394
395 RB_DECLARE_CALLBACKS(static, vma_gap_callbacks, struct vm_area_struct, vm_rb,
396                      unsigned long, rb_subtree_gap, vma_compute_subtree_gap)
397
398 /*
399  * Update augmented rbtree rb_subtree_gap values after vma->vm_start or
400  * vma->vm_prev->vm_end values changed, without modifying the vma's position
401  * in the rbtree.
402  */
403 static void vma_gap_update(struct vm_area_struct *vma)
404 {
405         /*
406          * As it turns out, RB_DECLARE_CALLBACKS() already created a callback
407          * function that does exacltly what we want.
408          */
409         vma_gap_callbacks_propagate(&vma->vm_rb, NULL);
410 }
411
412 static inline void vma_rb_insert(struct vm_area_struct *vma,
413                                  struct rb_root *root)
414 {
415         /* All rb_subtree_gap values must be consistent prior to insertion */
416         validate_mm_rb(root, NULL);
417
418         rb_insert_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
419 }
420
421 static void __vma_rb_erase(struct vm_area_struct *vma, struct rb_root *root)
422 {
423         /*
424          * Note rb_erase_augmented is a fairly large inline function,
425          * so make sure we instantiate it only once with our desired
426          * augmented rbtree callbacks.
427          */
428         rb_erase_augmented(&vma->vm_rb, root, &vma_gap_callbacks);
429 }
430
431 static __always_inline void vma_rb_erase_ignore(struct vm_area_struct *vma,
432                                                 struct rb_root *root,
433                                                 struct vm_area_struct *ignore)
434 {
435         /*
436          * All rb_subtree_gap values must be consistent prior to erase,
437          * with the possible exception of the "next" vma being erased if
438          * next->vm_start was reduced.
439          */
440         validate_mm_rb(root, ignore);
441
442         __vma_rb_erase(vma, root);
443 }
444
445 static __always_inline void vma_rb_erase(struct vm_area_struct *vma,
446                                          struct rb_root *root)
447 {
448         /*
449          * All rb_subtree_gap values must be consistent prior to erase,
450          * with the possible exception of the vma being erased.
451          */
452         validate_mm_rb(root, vma);
453
454         __vma_rb_erase(vma, root);
455 }
456
457 /*
458  * vma has some anon_vma assigned, and is already inserted on that
459  * anon_vma's interval trees.
460  *
461  * Before updating the vma's vm_start / vm_end / vm_pgoff fields, the
462  * vma must be removed from the anon_vma's interval trees using
463  * anon_vma_interval_tree_pre_update_vma().
464  *
465  * After the update, the vma will be reinserted using
466  * anon_vma_interval_tree_post_update_vma().
467  *
468  * The entire update must be protected by exclusive mmap_sem and by
469  * the root anon_vma's mutex.
470  */
471 static inline void
472 anon_vma_interval_tree_pre_update_vma(struct vm_area_struct *vma)
473 {
474         struct anon_vma_chain *avc;
475
476         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
477                 anon_vma_interval_tree_remove(avc, &avc->anon_vma->rb_root);
478 }
479
480 static inline void
481 anon_vma_interval_tree_post_update_vma(struct vm_area_struct *vma)
482 {
483         struct anon_vma_chain *avc;
484
485         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
486                 anon_vma_interval_tree_insert(avc, &avc->anon_vma->rb_root);
487 }
488
489 static int find_vma_links(struct mm_struct *mm, unsigned long addr,
490                 unsigned long end, struct vm_area_struct **pprev,
491                 struct rb_node ***rb_link, struct rb_node **rb_parent)
492 {
493         struct rb_node **__rb_link, *__rb_parent, *rb_prev;
494
495         __rb_link = &mm->mm_rb.rb_node;
496         rb_prev = __rb_parent = NULL;
497
498         while (*__rb_link) {
499                 struct vm_area_struct *vma_tmp;
500
501                 __rb_parent = *__rb_link;
502                 vma_tmp = rb_entry(__rb_parent, struct vm_area_struct, vm_rb);
503
504                 if (vma_tmp->vm_end > addr) {
505                         /* Fail if an existing vma overlaps the area */
506                         if (vma_tmp->vm_start < end)
507                                 return -ENOMEM;
508                         __rb_link = &__rb_parent->rb_left;
509                 } else {
510                         rb_prev = __rb_parent;
511                         __rb_link = &__rb_parent->rb_right;
512                 }
513         }
514
515         *pprev = NULL;
516         if (rb_prev)
517                 *pprev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);
518         *rb_link = __rb_link;
519         *rb_parent = __rb_parent;
520         return 0;
521 }
522
523 static unsigned long count_vma_pages_range(struct mm_struct *mm,
524                 unsigned long addr, unsigned long end)
525 {
526         unsigned long nr_pages = 0;
527         struct vm_area_struct *vma;
528
529         /* Find first overlaping mapping */
530         vma = find_vma_intersection(mm, addr, end);
531         if (!vma)
532                 return 0;
533
534         nr_pages = (min(end, vma->vm_end) -
535                 max(addr, vma->vm_start)) >> PAGE_SHIFT;
536
537         /* Iterate over the rest of the overlaps */
538         for (vma = vma->vm_next; vma; vma = vma->vm_next) {
539                 unsigned long overlap_len;
540
541                 if (vma->vm_start > end)
542                         break;
543
544                 overlap_len = min(end, vma->vm_end) - vma->vm_start;
545                 nr_pages += overlap_len >> PAGE_SHIFT;
546         }
547
548         return nr_pages;
549 }
550
551 void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
552                 struct rb_node **rb_link, struct rb_node *rb_parent)
553 {
554         /* Update tracking information for the gap following the new vma. */
555         if (vma->vm_next)
556                 vma_gap_update(vma->vm_next);
557         else
558                 mm->highest_vm_end = vm_end_gap(vma);
559
560         /*
561          * vma->vm_prev wasn't known when we followed the rbtree to find the
562          * correct insertion point for that vma. As a result, we could not
563          * update the vma vm_rb parents rb_subtree_gap values on the way down.
564          * So, we first insert the vma with a zero rb_subtree_gap value
565          * (to be consistent with what we did on the way down), and then
566          * immediately update the gap to the correct value. Finally we
567          * rebalance the rbtree after all augmented values have been set.
568          */
569         rb_link_node(&vma->vm_rb, rb_parent, rb_link);
570         vma->rb_subtree_gap = 0;
571         vma_gap_update(vma);
572         vma_rb_insert(vma, &mm->mm_rb);
573 }
574
575 static void __vma_link_file(struct vm_area_struct *vma)
576 {
577         struct file *file;
578
579         file = vma->vm_file;
580         if (file) {
581                 struct address_space *mapping = file->f_mapping;
582
583                 if (vma->vm_flags & VM_DENYWRITE)
584                         atomic_dec(&file_inode(file)->i_writecount);
585                 if (vma->vm_flags & VM_SHARED)
586                         atomic_inc(&mapping->i_mmap_writable);
587
588                 flush_dcache_mmap_lock(mapping);
589                 vma_interval_tree_insert(vma, &mapping->i_mmap);
590                 flush_dcache_mmap_unlock(mapping);
591         }
592 }
593
594 static void
595 __vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
596         struct vm_area_struct *prev, struct rb_node **rb_link,
597         struct rb_node *rb_parent)
598 {
599         __vma_link_list(mm, vma, prev, rb_parent);
600         __vma_link_rb(mm, vma, rb_link, rb_parent);
601 }
602
603 static void vma_link(struct mm_struct *mm, struct vm_area_struct *vma,
604                         struct vm_area_struct *prev, struct rb_node **rb_link,
605                         struct rb_node *rb_parent)
606 {
607         struct address_space *mapping = NULL;
608
609         if (vma->vm_file) {
610                 mapping = vma->vm_file->f_mapping;
611                 i_mmap_lock_write(mapping);
612         }
613
614         __vma_link(mm, vma, prev, rb_link, rb_parent);
615         __vma_link_file(vma);
616
617         if (mapping)
618                 i_mmap_unlock_write(mapping);
619
620         mm->map_count++;
621         validate_mm(mm);
622 }
623
624 /*
625  * Helper for vma_adjust() in the split_vma insert case: insert a vma into the
626  * mm's list and rbtree.  It has already been inserted into the interval tree.
627  */
628 static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
629 {
630         struct vm_area_struct *prev;
631         struct rb_node **rb_link, *rb_parent;
632
633         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
634                            &prev, &rb_link, &rb_parent))
635                 BUG();
636         __vma_link(mm, vma, prev, rb_link, rb_parent);
637         mm->map_count++;
638 }
639
640 static __always_inline void __vma_unlink_common(struct mm_struct *mm,
641                                                 struct vm_area_struct *vma,
642                                                 struct vm_area_struct *prev,
643                                                 bool has_prev,
644                                                 struct vm_area_struct *ignore)
645 {
646         struct vm_area_struct *next;
647
648         vma_rb_erase_ignore(vma, &mm->mm_rb, ignore);
649         next = vma->vm_next;
650         if (has_prev)
651                 prev->vm_next = next;
652         else {
653                 prev = vma->vm_prev;
654                 if (prev)
655                         prev->vm_next = next;
656                 else
657                         mm->mmap = next;
658         }
659         if (next)
660                 next->vm_prev = prev;
661
662         /* Kill the cache */
663         vmacache_invalidate(mm);
664 }
665
666 static inline void __vma_unlink_prev(struct mm_struct *mm,
667                                      struct vm_area_struct *vma,
668                                      struct vm_area_struct *prev)
669 {
670         __vma_unlink_common(mm, vma, prev, true, vma);
671 }
672
673 /*
674  * We cannot adjust vm_start, vm_end, vm_pgoff fields of a vma that
675  * is already present in an i_mmap tree without adjusting the tree.
676  * The following helper function should be used when such adjustments
677  * are necessary.  The "insert" vma (if any) is to be inserted
678  * before we drop the necessary locks.
679  */
680 int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
681         unsigned long end, pgoff_t pgoff, struct vm_area_struct *insert,
682         struct vm_area_struct *expand)
683 {
684         struct mm_struct *mm = vma->vm_mm;
685         struct vm_area_struct *next = vma->vm_next, *orig_vma = vma;
686         struct address_space *mapping = NULL;
687         struct rb_root *root = NULL;
688         struct anon_vma *anon_vma = NULL;
689         struct file *file = vma->vm_file;
690         bool start_changed = false, end_changed = false;
691         long adjust_next = 0;
692         int remove_next = 0;
693
694         if (next && !insert) {
695                 struct vm_area_struct *exporter = NULL, *importer = NULL;
696
697                 if (end >= next->vm_end) {
698                         /*
699                          * vma expands, overlapping all the next, and
700                          * perhaps the one after too (mprotect case 6).
701                          * The only other cases that gets here are
702                          * case 1, case 7 and case 8.
703                          */
704                         if (next == expand) {
705                                 /*
706                                  * The only case where we don't expand "vma"
707                                  * and we expand "next" instead is case 8.
708                                  */
709                                 VM_WARN_ON(end != next->vm_end);
710                                 /*
711                                  * remove_next == 3 means we're
712                                  * removing "vma" and that to do so we
713                                  * swapped "vma" and "next".
714                                  */
715                                 remove_next = 3;
716                                 VM_WARN_ON(file != next->vm_file);
717                                 swap(vma, next);
718                         } else {
719                                 VM_WARN_ON(expand != vma);
720                                 /*
721                                  * case 1, 6, 7, remove_next == 2 is case 6,
722                                  * remove_next == 1 is case 1 or 7.
723                                  */
724                                 remove_next = 1 + (end > next->vm_end);
725                                 VM_WARN_ON(remove_next == 2 &&
726                                            end != next->vm_next->vm_end);
727                                 VM_WARN_ON(remove_next == 1 &&
728                                            end != next->vm_end);
729                                 /* trim end to next, for case 6 first pass */
730                                 end = next->vm_end;
731                         }
732
733                         exporter = next;
734                         importer = vma;
735
736                         /*
737                          * If next doesn't have anon_vma, import from vma after
738                          * next, if the vma overlaps with it.
739                          */
740                         if (remove_next == 2 && !next->anon_vma)
741                                 exporter = next->vm_next;
742
743                 } else if (end > next->vm_start) {
744                         /*
745                          * vma expands, overlapping part of the next:
746                          * mprotect case 5 shifting the boundary up.
747                          */
748                         adjust_next = (end - next->vm_start) >> PAGE_SHIFT;
749                         exporter = next;
750                         importer = vma;
751                         VM_WARN_ON(expand != importer);
752                 } else if (end < vma->vm_end) {
753                         /*
754                          * vma shrinks, and !insert tells it's not
755                          * split_vma inserting another: so it must be
756                          * mprotect case 4 shifting the boundary down.
757                          */
758                         adjust_next = -((vma->vm_end - end) >> PAGE_SHIFT);
759                         exporter = vma;
760                         importer = next;
761                         VM_WARN_ON(expand != importer);
762                 }
763
764                 /*
765                  * Easily overlooked: when mprotect shifts the boundary,
766                  * make sure the expanding vma has anon_vma set if the
767                  * shrinking vma had, to cover any anon pages imported.
768                  */
769                 if (exporter && exporter->anon_vma && !importer->anon_vma) {
770                         int error;
771
772                         importer->anon_vma = exporter->anon_vma;
773                         error = anon_vma_clone(importer, exporter);
774                         if (error)
775                                 return error;
776                 }
777         }
778 again:
779         vma_adjust_trans_huge(orig_vma, start, end, adjust_next);
780
781         if (file) {
782                 mapping = file->f_mapping;
783                 root = &mapping->i_mmap;
784                 uprobe_munmap(vma, vma->vm_start, vma->vm_end);
785
786                 if (adjust_next)
787                         uprobe_munmap(next, next->vm_start, next->vm_end);
788
789                 i_mmap_lock_write(mapping);
790                 if (insert) {
791                         /*
792                          * Put into interval tree now, so instantiated pages
793                          * are visible to arm/parisc __flush_dcache_page
794                          * throughout; but we cannot insert into address
795                          * space until vma start or end is updated.
796                          */
797                         __vma_link_file(insert);
798                 }
799         }
800
801         anon_vma = vma->anon_vma;
802         if (!anon_vma && adjust_next)
803                 anon_vma = next->anon_vma;
804         if (anon_vma) {
805                 VM_WARN_ON(adjust_next && next->anon_vma &&
806                            anon_vma != next->anon_vma);
807                 anon_vma_lock_write(anon_vma);
808                 anon_vma_interval_tree_pre_update_vma(vma);
809                 if (adjust_next)
810                         anon_vma_interval_tree_pre_update_vma(next);
811         }
812
813         if (root) {
814                 flush_dcache_mmap_lock(mapping);
815                 vma_interval_tree_remove(vma, root);
816                 if (adjust_next)
817                         vma_interval_tree_remove(next, root);
818         }
819
820         if (start != vma->vm_start) {
821                 vma->vm_start = start;
822                 start_changed = true;
823         }
824         if (end != vma->vm_end) {
825                 vma->vm_end = end;
826                 end_changed = true;
827         }
828         vma->vm_pgoff = pgoff;
829         if (adjust_next) {
830                 next->vm_start += adjust_next << PAGE_SHIFT;
831                 next->vm_pgoff += adjust_next;
832         }
833
834         if (root) {
835                 if (adjust_next)
836                         vma_interval_tree_insert(next, root);
837                 vma_interval_tree_insert(vma, root);
838                 flush_dcache_mmap_unlock(mapping);
839         }
840
841         if (remove_next) {
842                 /*
843                  * vma_merge has merged next into vma, and needs
844                  * us to remove next before dropping the locks.
845                  */
846                 if (remove_next != 3)
847                         __vma_unlink_prev(mm, next, vma);
848                 else
849                         /*
850                          * vma is not before next if they've been
851                          * swapped.
852                          *
853                          * pre-swap() next->vm_start was reduced so
854                          * tell validate_mm_rb to ignore pre-swap()
855                          * "next" (which is stored in post-swap()
856                          * "vma").
857                          */
858                         __vma_unlink_common(mm, next, NULL, false, vma);
859                 if (file)
860                         __remove_shared_vm_struct(next, file, mapping);
861         } else if (insert) {
862                 /*
863                  * split_vma has split insert from vma, and needs
864                  * us to insert it before dropping the locks
865                  * (it may either follow vma or precede it).
866                  */
867                 __insert_vm_struct(mm, insert);
868         } else {
869                 if (start_changed)
870                         vma_gap_update(vma);
871                 if (end_changed) {
872                         if (!next)
873                                 mm->highest_vm_end = vm_end_gap(vma);
874                         else if (!adjust_next)
875                                 vma_gap_update(next);
876                 }
877         }
878
879         if (anon_vma) {
880                 anon_vma_interval_tree_post_update_vma(vma);
881                 if (adjust_next)
882                         anon_vma_interval_tree_post_update_vma(next);
883                 anon_vma_unlock_write(anon_vma);
884         }
885         if (mapping)
886                 i_mmap_unlock_write(mapping);
887
888         if (root) {
889                 uprobe_mmap(vma);
890
891                 if (adjust_next)
892                         uprobe_mmap(next);
893         }
894
895         if (remove_next) {
896                 if (file) {
897                         uprobe_munmap(next, next->vm_start, next->vm_end);
898                         fput(file);
899                 }
900                 if (next->anon_vma)
901                         anon_vma_merge(vma, next);
902                 mm->map_count--;
903                 mpol_put(vma_policy(next));
904                 kmem_cache_free(vm_area_cachep, next);
905                 /*
906                  * In mprotect's case 6 (see comments on vma_merge),
907                  * we must remove another next too. It would clutter
908                  * up the code too much to do both in one go.
909                  */
910                 if (remove_next != 3) {
911                         /*
912                          * If "next" was removed and vma->vm_end was
913                          * expanded (up) over it, in turn
914                          * "next->vm_prev->vm_end" changed and the
915                          * "vma->vm_next" gap must be updated.
916                          */
917                         next = vma->vm_next;
918                 } else {
919                         /*
920                          * For the scope of the comment "next" and
921                          * "vma" considered pre-swap(): if "vma" was
922                          * removed, next->vm_start was expanded (down)
923                          * over it and the "next" gap must be updated.
924                          * Because of the swap() the post-swap() "vma"
925                          * actually points to pre-swap() "next"
926                          * (post-swap() "next" as opposed is now a
927                          * dangling pointer).
928                          */
929                         next = vma;
930                 }
931                 if (remove_next == 2) {
932                         remove_next = 1;
933                         end = next->vm_end;
934                         goto again;
935                 }
936                 else if (next)
937                         vma_gap_update(next);
938                 else {
939                         /*
940                          * If remove_next == 2 we obviously can't
941                          * reach this path.
942                          *
943                          * If remove_next == 3 we can't reach this
944                          * path because pre-swap() next is always not
945                          * NULL. pre-swap() "next" is not being
946                          * removed and its next->vm_end is not altered
947                          * (and furthermore "end" already matches
948                          * next->vm_end in remove_next == 3).
949                          *
950                          * We reach this only in the remove_next == 1
951                          * case if the "next" vma that was removed was
952                          * the highest vma of the mm. However in such
953                          * case next->vm_end == "end" and the extended
954                          * "vma" has vma->vm_end == next->vm_end so
955                          * mm->highest_vm_end doesn't need any update
956                          * in remove_next == 1 case.
957                          */
958                         VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma));
959                 }
960         }
961         if (insert && file)
962                 uprobe_mmap(insert);
963
964         validate_mm(mm);
965
966         return 0;
967 }
968
969 /*
970  * If the vma has a ->close operation then the driver probably needs to release
971  * per-vma resources, so we don't attempt to merge those.
972  */
973 static inline int is_mergeable_vma(struct vm_area_struct *vma,
974                                 struct file *file, unsigned long vm_flags,
975                                 struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
976 {
977         /*
978          * VM_SOFTDIRTY should not prevent from VMA merging, if we
979          * match the flags but dirty bit -- the caller should mark
980          * merged VMA as dirty. If dirty bit won't be excluded from
981          * comparison, we increase pressue on the memory system forcing
982          * the kernel to generate new VMAs when old one could be
983          * extended instead.
984          */
985         if ((vma->vm_flags ^ vm_flags) & ~VM_SOFTDIRTY)
986                 return 0;
987         if (vma->vm_file != file)
988                 return 0;
989         if (vma->vm_ops && vma->vm_ops->close)
990                 return 0;
991         if (!is_mergeable_vm_userfaultfd_ctx(vma, vm_userfaultfd_ctx))
992                 return 0;
993         return 1;
994 }
995
996 static inline int is_mergeable_anon_vma(struct anon_vma *anon_vma1,
997                                         struct anon_vma *anon_vma2,
998                                         struct vm_area_struct *vma)
999 {
1000         /*
1001          * The list_is_singular() test is to avoid merging VMA cloned from
1002          * parents. This can improve scalability caused by anon_vma lock.
1003          */
1004         if ((!anon_vma1 || !anon_vma2) && (!vma ||
1005                 list_is_singular(&vma->anon_vma_chain)))
1006                 return 1;
1007         return anon_vma1 == anon_vma2;
1008 }
1009
1010 /*
1011  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1012  * in front of (at a lower virtual address and file offset than) the vma.
1013  *
1014  * We cannot merge two vmas if they have differently assigned (non-NULL)
1015  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1016  *
1017  * We don't check here for the merged mmap wrapping around the end of pagecache
1018  * indices (16TB on ia32) because do_mmap_pgoff() does not permit mmap's which
1019  * wrap, nor mmaps which cover the final page at index -1UL.
1020  */
1021 static int
1022 can_vma_merge_before(struct vm_area_struct *vma, unsigned long vm_flags,
1023                      struct anon_vma *anon_vma, struct file *file,
1024                      pgoff_t vm_pgoff,
1025                      struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1026 {
1027         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1028             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1029                 if (vma->vm_pgoff == vm_pgoff)
1030                         return 1;
1031         }
1032         return 0;
1033 }
1034
1035 /*
1036  * Return true if we can merge this (vm_flags,anon_vma,file,vm_pgoff)
1037  * beyond (at a higher virtual address and file offset than) the vma.
1038  *
1039  * We cannot merge two vmas if they have differently assigned (non-NULL)
1040  * anon_vmas, nor if same anon_vma is assigned but offsets incompatible.
1041  */
1042 static int
1043 can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags,
1044                     struct anon_vma *anon_vma, struct file *file,
1045                     pgoff_t vm_pgoff,
1046                     struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1047 {
1048         if (is_mergeable_vma(vma, file, vm_flags, vm_userfaultfd_ctx) &&
1049             is_mergeable_anon_vma(anon_vma, vma->anon_vma, vma)) {
1050                 pgoff_t vm_pglen;
1051                 vm_pglen = vma_pages(vma);
1052                 if (vma->vm_pgoff + vm_pglen == vm_pgoff)
1053                         return 1;
1054         }
1055         return 0;
1056 }
1057
1058 /*
1059  * Given a mapping request (addr,end,vm_flags,file,pgoff), figure out
1060  * whether that can be merged with its predecessor or its successor.
1061  * Or both (it neatly fills a hole).
1062  *
1063  * In most cases - when called for mmap, brk or mremap - [addr,end) is
1064  * certain not to be mapped by the time vma_merge is called; but when
1065  * called for mprotect, it is certain to be already mapped (either at
1066  * an offset within prev, or at the start of next), and the flags of
1067  * this area are about to be changed to vm_flags - and the no-change
1068  * case has already been eliminated.
1069  *
1070  * The following mprotect cases have to be considered, where AAAA is
1071  * the area passed down from mprotect_fixup, never extending beyond one
1072  * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after:
1073  *
1074  *     AAAA             AAAA                AAAA          AAAA
1075  *    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPPPNNNNNN    PPPPNNNNXXXX
1076  *    cannot merge    might become    might become    might become
1077  *                    PPNNNNNNNNNN    PPPPPPPPPPNN    PPPPPPPPPPPP 6 or
1078  *    mmap, brk or    case 4 below    case 5 below    PPPPPPPPXXXX 7 or
1079  *    mremap move:                                    PPPPXXXXXXXX 8
1080  *        AAAA
1081  *    PPPP    NNNN    PPPPPPPPPPPP    PPPPPPPPNNNN    PPPPNNNNNNNN
1082  *    might become    case 1 below    case 2 below    case 3 below
1083  *
1084  * It is important for case 8 that the the vma NNNN overlapping the
1085  * region AAAA is never going to extended over XXXX. Instead XXXX must
1086  * be extended in region AAAA and NNNN must be removed. This way in
1087  * all cases where vma_merge succeeds, the moment vma_adjust drops the
1088  * rmap_locks, the properties of the merged vma will be already
1089  * correct for the whole merged range. Some of those properties like
1090  * vm_page_prot/vm_flags may be accessed by rmap_walks and they must
1091  * be correct for the whole merged range immediately after the
1092  * rmap_locks are released. Otherwise if XXXX would be removed and
1093  * NNNN would be extended over the XXXX range, remove_migration_ptes
1094  * or other rmap walkers (if working on addresses beyond the "end"
1095  * parameter) may establish ptes with the wrong permissions of NNNN
1096  * instead of the right permissions of XXXX.
1097  */
1098 struct vm_area_struct *vma_merge(struct mm_struct *mm,
1099                         struct vm_area_struct *prev, unsigned long addr,
1100                         unsigned long end, unsigned long vm_flags,
1101                         struct anon_vma *anon_vma, struct file *file,
1102                         pgoff_t pgoff, struct mempolicy *policy,
1103                         struct vm_userfaultfd_ctx vm_userfaultfd_ctx)
1104 {
1105         pgoff_t pglen = (end - addr) >> PAGE_SHIFT;
1106         struct vm_area_struct *area, *next;
1107         int err;
1108
1109         /*
1110          * We later require that vma->vm_flags == vm_flags,
1111          * so this tests vma->vm_flags & VM_SPECIAL, too.
1112          */
1113         if (vm_flags & VM_SPECIAL)
1114                 return NULL;
1115
1116         if (prev)
1117                 next = prev->vm_next;
1118         else
1119                 next = mm->mmap;
1120         area = next;
1121         if (area && area->vm_end == end)                /* cases 6, 7, 8 */
1122                 next = next->vm_next;
1123
1124         /* verify some invariant that must be enforced by the caller */
1125         VM_WARN_ON(prev && addr <= prev->vm_start);
1126         VM_WARN_ON(area && end > area->vm_end);
1127         VM_WARN_ON(addr >= end);
1128
1129         /*
1130          * Can it merge with the predecessor?
1131          */
1132         if (prev && prev->vm_end == addr &&
1133                         mpol_equal(vma_policy(prev), policy) &&
1134                         can_vma_merge_after(prev, vm_flags,
1135                                             anon_vma, file, pgoff,
1136                                             vm_userfaultfd_ctx)) {
1137                 /*
1138                  * OK, it can.  Can we now merge in the successor as well?
1139                  */
1140                 if (next && end == next->vm_start &&
1141                                 mpol_equal(policy, vma_policy(next)) &&
1142                                 can_vma_merge_before(next, vm_flags,
1143                                                      anon_vma, file,
1144                                                      pgoff+pglen,
1145                                                      vm_userfaultfd_ctx) &&
1146                                 is_mergeable_anon_vma(prev->anon_vma,
1147                                                       next->anon_vma, NULL)) {
1148                                                         /* cases 1, 6 */
1149                         err = __vma_adjust(prev, prev->vm_start,
1150                                          next->vm_end, prev->vm_pgoff, NULL,
1151                                          prev);
1152                 } else                                  /* cases 2, 5, 7 */
1153                         err = __vma_adjust(prev, prev->vm_start,
1154                                          end, prev->vm_pgoff, NULL, prev);
1155                 if (err)
1156                         return NULL;
1157                 khugepaged_enter_vma_merge(prev, vm_flags);
1158                 return prev;
1159         }
1160
1161         /*
1162          * Can this new request be merged in front of next?
1163          */
1164         if (next && end == next->vm_start &&
1165                         mpol_equal(policy, vma_policy(next)) &&
1166                         can_vma_merge_before(next, vm_flags,
1167                                              anon_vma, file, pgoff+pglen,
1168                                              vm_userfaultfd_ctx)) {
1169                 if (prev && addr < prev->vm_end)        /* case 4 */
1170                         err = __vma_adjust(prev, prev->vm_start,
1171                                          addr, prev->vm_pgoff, NULL, next);
1172                 else {                                  /* cases 3, 8 */
1173                         err = __vma_adjust(area, addr, next->vm_end,
1174                                          next->vm_pgoff - pglen, NULL, next);
1175                         /*
1176                          * In case 3 area is already equal to next and
1177                          * this is a noop, but in case 8 "area" has
1178                          * been removed and next was expanded over it.
1179                          */
1180                         area = next;
1181                 }
1182                 if (err)
1183                         return NULL;
1184                 khugepaged_enter_vma_merge(area, vm_flags);
1185                 return area;
1186         }
1187
1188         return NULL;
1189 }
1190
1191 /*
1192  * Rough compatbility check to quickly see if it's even worth looking
1193  * at sharing an anon_vma.
1194  *
1195  * They need to have the same vm_file, and the flags can only differ
1196  * in things that mprotect may change.
1197  *
1198  * NOTE! The fact that we share an anon_vma doesn't _have_ to mean that
1199  * we can merge the two vma's. For example, we refuse to merge a vma if
1200  * there is a vm_ops->close() function, because that indicates that the
1201  * driver is doing some kind of reference counting. But that doesn't
1202  * really matter for the anon_vma sharing case.
1203  */
1204 static int anon_vma_compatible(struct vm_area_struct *a, struct vm_area_struct *b)
1205 {
1206         return a->vm_end == b->vm_start &&
1207                 mpol_equal(vma_policy(a), vma_policy(b)) &&
1208                 a->vm_file == b->vm_file &&
1209                 !((a->vm_flags ^ b->vm_flags) & ~(VM_READ|VM_WRITE|VM_EXEC|VM_SOFTDIRTY)) &&
1210                 b->vm_pgoff == a->vm_pgoff + ((b->vm_start - a->vm_start) >> PAGE_SHIFT);
1211 }
1212
1213 /*
1214  * Do some basic sanity checking to see if we can re-use the anon_vma
1215  * from 'old'. The 'a'/'b' vma's are in VM order - one of them will be
1216  * the same as 'old', the other will be the new one that is trying
1217  * to share the anon_vma.
1218  *
1219  * NOTE! This runs with mm_sem held for reading, so it is possible that
1220  * the anon_vma of 'old' is concurrently in the process of being set up
1221  * by another page fault trying to merge _that_. But that's ok: if it
1222  * is being set up, that automatically means that it will be a singleton
1223  * acceptable for merging, so we can do all of this optimistically. But
1224  * we do that READ_ONCE() to make sure that we never re-load the pointer.
1225  *
1226  * IOW: that the "list_is_singular()" test on the anon_vma_chain only
1227  * matters for the 'stable anon_vma' case (ie the thing we want to avoid
1228  * is to return an anon_vma that is "complex" due to having gone through
1229  * a fork).
1230  *
1231  * We also make sure that the two vma's are compatible (adjacent,
1232  * and with the same memory policies). That's all stable, even with just
1233  * a read lock on the mm_sem.
1234  */
1235 static struct anon_vma *reusable_anon_vma(struct vm_area_struct *old, struct vm_area_struct *a, struct vm_area_struct *b)
1236 {
1237         if (anon_vma_compatible(a, b)) {
1238                 struct anon_vma *anon_vma = READ_ONCE(old->anon_vma);
1239
1240                 if (anon_vma && list_is_singular(&old->anon_vma_chain))
1241                         return anon_vma;
1242         }
1243         return NULL;
1244 }
1245
1246 /*
1247  * find_mergeable_anon_vma is used by anon_vma_prepare, to check
1248  * neighbouring vmas for a suitable anon_vma, before it goes off
1249  * to allocate a new anon_vma.  It checks because a repetitive
1250  * sequence of mprotects and faults may otherwise lead to distinct
1251  * anon_vmas being allocated, preventing vma merge in subsequent
1252  * mprotect.
1253  */
1254 struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
1255 {
1256         struct anon_vma *anon_vma;
1257         struct vm_area_struct *near;
1258
1259         near = vma->vm_next;
1260         if (!near)
1261                 goto try_prev;
1262
1263         anon_vma = reusable_anon_vma(near, vma, near);
1264         if (anon_vma)
1265                 return anon_vma;
1266 try_prev:
1267         near = vma->vm_prev;
1268         if (!near)
1269                 goto none;
1270
1271         anon_vma = reusable_anon_vma(near, near, vma);
1272         if (anon_vma)
1273                 return anon_vma;
1274 none:
1275         /*
1276          * There's no absolute need to look only at touching neighbours:
1277          * we could search further afield for "compatible" anon_vmas.
1278          * But it would probably just be a waste of time searching,
1279          * or lead to too many vmas hanging off the same anon_vma.
1280          * We're trying to allow mprotect remerging later on,
1281          * not trying to minimize memory used for anon_vmas.
1282          */
1283         return NULL;
1284 }
1285
1286 /*
1287  * If a hint addr is less than mmap_min_addr change hint to be as
1288  * low as possible but still greater than mmap_min_addr
1289  */
1290 static inline unsigned long round_hint_to_min(unsigned long hint)
1291 {
1292         hint &= PAGE_MASK;
1293         if (((void *)hint != NULL) &&
1294             (hint < mmap_min_addr))
1295                 return PAGE_ALIGN(mmap_min_addr);
1296         return hint;
1297 }
1298
1299 static inline int mlock_future_check(struct mm_struct *mm,
1300                                      unsigned long flags,
1301                                      unsigned long len)
1302 {
1303         unsigned long locked, lock_limit;
1304
1305         /*  mlock MCL_FUTURE? */
1306         if (flags & VM_LOCKED) {
1307                 locked = len >> PAGE_SHIFT;
1308                 locked += mm->locked_vm;
1309                 lock_limit = rlimit(RLIMIT_MEMLOCK);
1310                 lock_limit >>= PAGE_SHIFT;
1311                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
1312                         return -EAGAIN;
1313         }
1314         return 0;
1315 }
1316
1317 /*
1318  * The caller must hold down_write(&current->mm->mmap_sem).
1319  */
1320 unsigned long do_mmap(struct file *file, unsigned long addr,
1321                         unsigned long len, unsigned long prot,
1322                         unsigned long flags, vm_flags_t vm_flags,
1323                         unsigned long pgoff, unsigned long *populate,
1324                         struct list_head *uf)
1325 {
1326         struct mm_struct *mm = current->mm;
1327         int pkey = 0;
1328
1329         *populate = 0;
1330
1331         if (!len)
1332                 return -EINVAL;
1333
1334         /*
1335          * Does the application expect PROT_READ to imply PROT_EXEC?
1336          *
1337          * (the exception is when the underlying filesystem is noexec
1338          *  mounted, in which case we dont add PROT_EXEC.)
1339          */
1340         if ((prot & PROT_READ) && (current->personality & READ_IMPLIES_EXEC))
1341                 if (!(file && path_noexec(&file->f_path)))
1342                         prot |= PROT_EXEC;
1343
1344         if (!(flags & MAP_FIXED))
1345                 addr = round_hint_to_min(addr);
1346
1347         /* Careful about overflows.. */
1348         len = PAGE_ALIGN(len);
1349         if (!len)
1350                 return -ENOMEM;
1351
1352         /* offset overflow? */
1353         if ((pgoff + (len >> PAGE_SHIFT)) < pgoff)
1354                 return -EOVERFLOW;
1355
1356         /* Too many mappings? */
1357         if (mm->map_count > sysctl_max_map_count)
1358                 return -ENOMEM;
1359
1360         /* Obtain the address to map to. we verify (or select) it and ensure
1361          * that it represents a valid section of the address space.
1362          */
1363         addr = get_unmapped_area(file, addr, len, pgoff, flags);
1364         if (offset_in_page(addr))
1365                 return addr;
1366
1367         if (prot == PROT_EXEC) {
1368                 pkey = execute_only_pkey(mm);
1369                 if (pkey < 0)
1370                         pkey = 0;
1371         }
1372
1373         /* Do simple checking here so the lower-level routines won't have
1374          * to. we assume access permissions have been handled by the open
1375          * of the memory object, so we don't do any here.
1376          */
1377         vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
1378                         mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
1379
1380         if (flags & MAP_LOCKED)
1381                 if (!can_do_mlock())
1382                         return -EPERM;
1383
1384         if (mlock_future_check(mm, vm_flags, len))
1385                 return -EAGAIN;
1386
1387         if (file) {
1388                 struct inode *inode = file_inode(file);
1389
1390                 switch (flags & MAP_TYPE) {
1391                 case MAP_SHARED:
1392                         if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE))
1393                                 return -EACCES;
1394
1395                         /*
1396                          * Make sure we don't allow writing to an append-only
1397                          * file..
1398                          */
1399                         if (IS_APPEND(inode) && (file->f_mode & FMODE_WRITE))
1400                                 return -EACCES;
1401
1402                         /*
1403                          * Make sure there are no mandatory locks on the file.
1404                          */
1405                         if (locks_verify_locked(file))
1406                                 return -EAGAIN;
1407
1408                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1409                         if (!(file->f_mode & FMODE_WRITE))
1410                                 vm_flags &= ~(VM_MAYWRITE | VM_SHARED);
1411
1412                         /* fall through */
1413                 case MAP_PRIVATE:
1414                         if (!(file->f_mode & FMODE_READ))
1415                                 return -EACCES;
1416                         if (path_noexec(&file->f_path)) {
1417                                 if (vm_flags & VM_EXEC)
1418                                         return -EPERM;
1419                                 vm_flags &= ~VM_MAYEXEC;
1420                         }
1421
1422                         if (!file->f_op->mmap)
1423                                 return -ENODEV;
1424                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1425                                 return -EINVAL;
1426                         break;
1427
1428                 default:
1429                         return -EINVAL;
1430                 }
1431         } else {
1432                 switch (flags & MAP_TYPE) {
1433                 case MAP_SHARED:
1434                         if (vm_flags & (VM_GROWSDOWN|VM_GROWSUP))
1435                                 return -EINVAL;
1436                         /*
1437                          * Ignore pgoff.
1438                          */
1439                         pgoff = 0;
1440                         vm_flags |= VM_SHARED | VM_MAYSHARE;
1441                         break;
1442                 case MAP_PRIVATE:
1443                         /*
1444                          * Set pgoff according to addr for anon_vma.
1445                          */
1446                         pgoff = addr >> PAGE_SHIFT;
1447                         break;
1448                 default:
1449                         return -EINVAL;
1450                 }
1451         }
1452
1453         /*
1454          * Set 'VM_NORESERVE' if we should not account for the
1455          * memory use of this mapping.
1456          */
1457         if (flags & MAP_NORESERVE) {
1458                 /* We honor MAP_NORESERVE if allowed to overcommit */
1459                 if (sysctl_overcommit_memory != OVERCOMMIT_NEVER)
1460                         vm_flags |= VM_NORESERVE;
1461
1462                 /* hugetlb applies strict overcommit unless MAP_NORESERVE */
1463                 if (file && is_file_hugepages(file))
1464                         vm_flags |= VM_NORESERVE;
1465         }
1466
1467         addr = mmap_region(file, addr, len, vm_flags, pgoff, uf);
1468         if (!IS_ERR_VALUE(addr) &&
1469             ((vm_flags & VM_LOCKED) ||
1470              (flags & (MAP_POPULATE | MAP_NONBLOCK)) == MAP_POPULATE))
1471                 *populate = len;
1472         return addr;
1473 }
1474
1475 SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
1476                 unsigned long, prot, unsigned long, flags,
1477                 unsigned long, fd, unsigned long, pgoff)
1478 {
1479         struct file *file = NULL;
1480         unsigned long retval;
1481
1482         if (!(flags & MAP_ANONYMOUS)) {
1483                 audit_mmap_fd(fd, flags);
1484                 file = fget(fd);
1485                 if (!file)
1486                         return -EBADF;
1487                 if (is_file_hugepages(file))
1488                         len = ALIGN(len, huge_page_size(hstate_file(file)));
1489                 retval = -EINVAL;
1490                 if (unlikely(flags & MAP_HUGETLB && !is_file_hugepages(file)))
1491                         goto out_fput;
1492         } else if (flags & MAP_HUGETLB) {
1493                 struct user_struct *user = NULL;
1494                 struct hstate *hs;
1495
1496                 hs = hstate_sizelog((flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1497                 if (!hs)
1498                         return -EINVAL;
1499
1500                 len = ALIGN(len, huge_page_size(hs));
1501                 /*
1502                  * VM_NORESERVE is used because the reservations will be
1503                  * taken when vm_ops->mmap() is called
1504                  * A dummy user value is used because we are not locking
1505                  * memory so no accounting is necessary
1506                  */
1507                 file = hugetlb_file_setup(HUGETLB_ANON_FILE, len,
1508                                 VM_NORESERVE,
1509                                 &user, HUGETLB_ANONHUGE_INODE,
1510                                 (flags >> MAP_HUGE_SHIFT) & MAP_HUGE_MASK);
1511                 if (IS_ERR(file))
1512                         return PTR_ERR(file);
1513         }
1514
1515         flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);
1516
1517         retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);
1518 out_fput:
1519         if (file)
1520                 fput(file);
1521         return retval;
1522 }
1523
1524 #ifdef __ARCH_WANT_SYS_OLD_MMAP
1525 struct mmap_arg_struct {
1526         unsigned long addr;
1527         unsigned long len;
1528         unsigned long prot;
1529         unsigned long flags;
1530         unsigned long fd;
1531         unsigned long offset;
1532 };
1533
1534 SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
1535 {
1536         struct mmap_arg_struct a;
1537
1538         if (copy_from_user(&a, arg, sizeof(a)))
1539                 return -EFAULT;
1540         if (offset_in_page(a.offset))
1541                 return -EINVAL;
1542
1543         return sys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
1544                               a.offset >> PAGE_SHIFT);
1545 }
1546 #endif /* __ARCH_WANT_SYS_OLD_MMAP */
1547
1548 /*
1549  * Some shared mappigns will want the pages marked read-only
1550  * to track write events. If so, we'll downgrade vm_page_prot
1551  * to the private version (using protection_map[] without the
1552  * VM_SHARED bit).
1553  */
1554 int vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot)
1555 {
1556         vm_flags_t vm_flags = vma->vm_flags;
1557         const struct vm_operations_struct *vm_ops = vma->vm_ops;
1558
1559         /* If it was private or non-writable, the write bit is already clear */
1560         if ((vm_flags & (VM_WRITE|VM_SHARED)) != ((VM_WRITE|VM_SHARED)))
1561                 return 0;
1562
1563         /* The backer wishes to know when pages are first written to? */
1564         if (vm_ops && (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite))
1565                 return 1;
1566
1567         /* The open routine did something to the protections that pgprot_modify
1568          * won't preserve? */
1569         if (pgprot_val(vm_page_prot) !=
1570             pgprot_val(vm_pgprot_modify(vm_page_prot, vm_flags)))
1571                 return 0;
1572
1573         /* Do we need to track softdirty? */
1574         if (IS_ENABLED(CONFIG_MEM_SOFT_DIRTY) && !(vm_flags & VM_SOFTDIRTY))
1575                 return 1;
1576
1577         /* Specialty mapping? */
1578         if (vm_flags & VM_PFNMAP)
1579                 return 0;
1580
1581         /* Can the mapping track the dirty pages? */
1582         return vma->vm_file && vma->vm_file->f_mapping &&
1583                 mapping_cap_account_dirty(vma->vm_file->f_mapping);
1584 }
1585
1586 /*
1587  * We account for memory if it's a private writeable mapping,
1588  * not hugepages and VM_NORESERVE wasn't set.
1589  */
1590 static inline int accountable_mapping(struct file *file, vm_flags_t vm_flags)
1591 {
1592         /*
1593          * hugetlb has its own accounting separate from the core VM
1594          * VM_HUGETLB may not be set yet so we cannot check for that flag.
1595          */
1596         if (file && is_file_hugepages(file))
1597                 return 0;
1598
1599         return (vm_flags & (VM_NORESERVE | VM_SHARED | VM_WRITE)) == VM_WRITE;
1600 }
1601
1602 unsigned long mmap_region(struct file *file, unsigned long addr,
1603                 unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
1604                 struct list_head *uf)
1605 {
1606         struct mm_struct *mm = current->mm;
1607         struct vm_area_struct *vma, *prev;
1608         int error;
1609         struct rb_node **rb_link, *rb_parent;
1610         unsigned long charged = 0;
1611
1612         /* Check against address space limit. */
1613         if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT)) {
1614                 unsigned long nr_pages;
1615
1616                 /*
1617                  * MAP_FIXED may remove pages of mappings that intersects with
1618                  * requested mapping. Account for the pages it would unmap.
1619                  */
1620                 nr_pages = count_vma_pages_range(mm, addr, addr + len);
1621
1622                 if (!may_expand_vm(mm, vm_flags,
1623                                         (len >> PAGE_SHIFT) - nr_pages))
1624                         return -ENOMEM;
1625         }
1626
1627         /* Clear old maps */
1628         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
1629                               &rb_parent)) {
1630                 if (do_munmap(mm, addr, len, uf))
1631                         return -ENOMEM;
1632         }
1633
1634         /*
1635          * Private writable mapping: check memory availability
1636          */
1637         if (accountable_mapping(file, vm_flags)) {
1638                 charged = len >> PAGE_SHIFT;
1639                 if (security_vm_enough_memory_mm(mm, charged))
1640                         return -ENOMEM;
1641                 vm_flags |= VM_ACCOUNT;
1642         }
1643
1644         /*
1645          * Can we just expand an old mapping?
1646          */
1647         vma = vma_merge(mm, prev, addr, addr + len, vm_flags,
1648                         NULL, file, pgoff, NULL, NULL_VM_UFFD_CTX);
1649         if (vma)
1650                 goto out;
1651
1652         /*
1653          * Determine the object being mapped and call the appropriate
1654          * specific mapper. the address has already been validated, but
1655          * not unmapped, but the maps are removed from the list.
1656          */
1657         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
1658         if (!vma) {
1659                 error = -ENOMEM;
1660                 goto unacct_error;
1661         }
1662
1663         vma->vm_mm = mm;
1664         vma->vm_start = addr;
1665         vma->vm_end = addr + len;
1666         vma->vm_flags = vm_flags;
1667         vma->vm_page_prot = vm_get_page_prot(vm_flags);
1668         vma->vm_pgoff = pgoff;
1669         INIT_LIST_HEAD(&vma->anon_vma_chain);
1670
1671         if (file) {
1672                 if (vm_flags & VM_DENYWRITE) {
1673                         error = deny_write_access(file);
1674                         if (error)
1675                                 goto free_vma;
1676                 }
1677                 if (vm_flags & VM_SHARED) {
1678                         error = mapping_map_writable(file->f_mapping);
1679                         if (error)
1680                                 goto allow_write_and_free_vma;
1681                 }
1682
1683                 /* ->mmap() can change vma->vm_file, but must guarantee that
1684                  * vma_link() below can deny write-access if VM_DENYWRITE is set
1685                  * and map writably if VM_SHARED is set. This usually means the
1686                  * new file must not have been exposed to user-space, yet.
1687                  */
1688                 vma->vm_file = get_file(file);
1689                 error = call_mmap(file, vma);
1690                 if (error)
1691                         goto unmap_and_free_vma;
1692
1693                 /* Can addr have changed??
1694                  *
1695                  * Answer: Yes, several device drivers can do it in their
1696                  *         f_op->mmap method. -DaveM
1697                  * Bug: If addr is changed, prev, rb_link, rb_parent should
1698                  *      be updated for vma_link()
1699                  */
1700                 WARN_ON_ONCE(addr != vma->vm_start);
1701
1702                 addr = vma->vm_start;
1703                 vm_flags = vma->vm_flags;
1704         } else if (vm_flags & VM_SHARED) {
1705                 error = shmem_zero_setup(vma);
1706                 if (error)
1707                         goto free_vma;
1708         }
1709
1710         vma_link(mm, vma, prev, rb_link, rb_parent);
1711         /* Once vma denies write, undo our temporary denial count */
1712         if (file) {
1713                 if (vm_flags & VM_SHARED)
1714                         mapping_unmap_writable(file->f_mapping);
1715                 if (vm_flags & VM_DENYWRITE)
1716                         allow_write_access(file);
1717         }
1718         file = vma->vm_file;
1719 out:
1720         perf_event_mmap(vma);
1721
1722         vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
1723         if (vm_flags & VM_LOCKED) {
1724                 if (!((vm_flags & VM_SPECIAL) || is_vm_hugetlb_page(vma) ||
1725                                         vma == get_gate_vma(current->mm)))
1726                         mm->locked_vm += (len >> PAGE_SHIFT);
1727                 else
1728                         vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
1729         }
1730
1731         if (file)
1732                 uprobe_mmap(vma);
1733
1734         /*
1735          * New (or expanded) vma always get soft dirty status.
1736          * Otherwise user-space soft-dirty page tracker won't
1737          * be able to distinguish situation when vma area unmapped,
1738          * then new mapped in-place (which must be aimed as
1739          * a completely new data area).
1740          */
1741         vma->vm_flags |= VM_SOFTDIRTY;
1742
1743         vma_set_page_prot(vma);
1744
1745         return addr;
1746
1747 unmap_and_free_vma:
1748         vma->vm_file = NULL;
1749         fput(file);
1750
1751         /* Undo any partial mapping done by a device driver. */
1752         unmap_region(mm, vma, prev, vma->vm_start, vma->vm_end);
1753         charged = 0;
1754         if (vm_flags & VM_SHARED)
1755                 mapping_unmap_writable(file->f_mapping);
1756 allow_write_and_free_vma:
1757         if (vm_flags & VM_DENYWRITE)
1758                 allow_write_access(file);
1759 free_vma:
1760         kmem_cache_free(vm_area_cachep, vma);
1761 unacct_error:
1762         if (charged)
1763                 vm_unacct_memory(charged);
1764         return error;
1765 }
1766
1767 unsigned long unmapped_area(struct vm_unmapped_area_info *info)
1768 {
1769         /*
1770          * We implement the search by looking for an rbtree node that
1771          * immediately follows a suitable gap. That is,
1772          * - gap_start = vma->vm_prev->vm_end <= info->high_limit - length;
1773          * - gap_end   = vma->vm_start        >= info->low_limit  + length;
1774          * - gap_end - gap_start >= length
1775          */
1776
1777         struct mm_struct *mm = current->mm;
1778         struct vm_area_struct *vma;
1779         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1780
1781         /* Adjust search length to account for worst case alignment overhead */
1782         length = info->length + info->align_mask;
1783         if (length < info->length)
1784                 return -ENOMEM;
1785
1786         /* Adjust search limits by the desired length */
1787         if (info->high_limit < length)
1788                 return -ENOMEM;
1789         high_limit = info->high_limit - length;
1790
1791         if (info->low_limit > high_limit)
1792                 return -ENOMEM;
1793         low_limit = info->low_limit + length;
1794
1795         /* Check if rbtree root looks promising */
1796         if (RB_EMPTY_ROOT(&mm->mm_rb))
1797                 goto check_highest;
1798         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1799         if (vma->rb_subtree_gap < length)
1800                 goto check_highest;
1801
1802         while (true) {
1803                 /* Visit left subtree if it looks promising */
1804                 gap_end = vm_start_gap(vma);
1805                 if (gap_end >= low_limit && vma->vm_rb.rb_left) {
1806                         struct vm_area_struct *left =
1807                                 rb_entry(vma->vm_rb.rb_left,
1808                                          struct vm_area_struct, vm_rb);
1809                         if (left->rb_subtree_gap >= length) {
1810                                 vma = left;
1811                                 continue;
1812                         }
1813                 }
1814
1815                 gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
1816 check_current:
1817                 /* Check if current node has a suitable gap */
1818                 if (gap_start > high_limit)
1819                         return -ENOMEM;
1820                 if (gap_end >= low_limit &&
1821                     gap_end > gap_start && gap_end - gap_start >= length)
1822                         goto found;
1823
1824                 /* Visit right subtree if it looks promising */
1825                 if (vma->vm_rb.rb_right) {
1826                         struct vm_area_struct *right =
1827                                 rb_entry(vma->vm_rb.rb_right,
1828                                          struct vm_area_struct, vm_rb);
1829                         if (right->rb_subtree_gap >= length) {
1830                                 vma = right;
1831                                 continue;
1832                         }
1833                 }
1834
1835                 /* Go back up the rbtree to find next candidate node */
1836                 while (true) {
1837                         struct rb_node *prev = &vma->vm_rb;
1838                         if (!rb_parent(prev))
1839                                 goto check_highest;
1840                         vma = rb_entry(rb_parent(prev),
1841                                        struct vm_area_struct, vm_rb);
1842                         if (prev == vma->vm_rb.rb_left) {
1843                                 gap_start = vm_end_gap(vma->vm_prev);
1844                                 gap_end = vm_start_gap(vma);
1845                                 goto check_current;
1846                         }
1847                 }
1848         }
1849
1850 check_highest:
1851         /* Check highest gap, which does not precede any rbtree node */
1852         gap_start = mm->highest_vm_end;
1853         gap_end = ULONG_MAX;  /* Only for VM_BUG_ON below */
1854         if (gap_start > high_limit)
1855                 return -ENOMEM;
1856
1857 found:
1858         /* We found a suitable gap. Clip it with the original low_limit. */
1859         if (gap_start < info->low_limit)
1860                 gap_start = info->low_limit;
1861
1862         /* Adjust gap address to the desired alignment */
1863         gap_start += (info->align_offset - gap_start) & info->align_mask;
1864
1865         VM_BUG_ON(gap_start + info->length > info->high_limit);
1866         VM_BUG_ON(gap_start + info->length > gap_end);
1867         return gap_start;
1868 }
1869
1870 unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
1871 {
1872         struct mm_struct *mm = current->mm;
1873         struct vm_area_struct *vma;
1874         unsigned long length, low_limit, high_limit, gap_start, gap_end;
1875
1876         /* Adjust search length to account for worst case alignment overhead */
1877         length = info->length + info->align_mask;
1878         if (length < info->length)
1879                 return -ENOMEM;
1880
1881         /*
1882          * Adjust search limits by the desired length.
1883          * See implementation comment at top of unmapped_area().
1884          */
1885         gap_end = info->high_limit;
1886         if (gap_end < length)
1887                 return -ENOMEM;
1888         high_limit = gap_end - length;
1889
1890         if (info->low_limit > high_limit)
1891                 return -ENOMEM;
1892         low_limit = info->low_limit + length;
1893
1894         /* Check highest gap, which does not precede any rbtree node */
1895         gap_start = mm->highest_vm_end;
1896         if (gap_start <= high_limit)
1897                 goto found_highest;
1898
1899         /* Check if rbtree root looks promising */
1900         if (RB_EMPTY_ROOT(&mm->mm_rb))
1901                 return -ENOMEM;
1902         vma = rb_entry(mm->mm_rb.rb_node, struct vm_area_struct, vm_rb);
1903         if (vma->rb_subtree_gap < length)
1904                 return -ENOMEM;
1905
1906         while (true) {
1907                 /* Visit right subtree if it looks promising */
1908                 gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0;
1909                 if (gap_start <= high_limit && vma->vm_rb.rb_right) {
1910                         struct vm_area_struct *right =
1911                                 rb_entry(vma->vm_rb.rb_right,
1912                                          struct vm_area_struct, vm_rb);
1913                         if (right->rb_subtree_gap >= length) {
1914                                 vma = right;
1915                                 continue;
1916                         }
1917                 }
1918
1919 check_current:
1920                 /* Check if current node has a suitable gap */
1921                 gap_end = vm_start_gap(vma);
1922                 if (gap_end < low_limit)
1923                         return -ENOMEM;
1924                 if (gap_start <= high_limit &&
1925                     gap_end > gap_start && gap_end - gap_start >= length)
1926                         goto found;
1927
1928                 /* Visit left subtree if it looks promising */
1929                 if (vma->vm_rb.rb_left) {
1930                         struct vm_area_struct *left =
1931                                 rb_entry(vma->vm_rb.rb_left,
1932                                          struct vm_area_struct, vm_rb);
1933                         if (left->rb_subtree_gap >= length) {
1934                                 vma = left;
1935                                 continue;
1936                         }
1937                 }
1938
1939                 /* Go back up the rbtree to find next candidate node */
1940                 while (true) {
1941                         struct rb_node *prev = &vma->vm_rb;
1942                         if (!rb_parent(prev))
1943                                 return -ENOMEM;
1944                         vma = rb_entry(rb_parent(prev),
1945                                        struct vm_area_struct, vm_rb);
1946                         if (prev == vma->vm_rb.rb_right) {
1947                                 gap_start = vma->vm_prev ?
1948                                         vm_end_gap(vma->vm_prev) : 0;
1949                                 goto check_current;
1950                         }
1951                 }
1952         }
1953
1954 found:
1955         /* We found a suitable gap. Clip it with the original high_limit. */
1956         if (gap_end > info->high_limit)
1957                 gap_end = info->high_limit;
1958
1959 found_highest:
1960         /* Compute highest gap address at the desired alignment */
1961         gap_end -= info->length;
1962         gap_end -= (gap_end - info->align_offset) & info->align_mask;
1963
1964         VM_BUG_ON(gap_end < info->low_limit);
1965         VM_BUG_ON(gap_end < gap_start);
1966         return gap_end;
1967 }
1968
1969 /* Get an address range which is currently unmapped.
1970  * For shmat() with addr=0.
1971  *
1972  * Ugly calling convention alert:
1973  * Return value with the low bits set means error value,
1974  * ie
1975  *      if (ret & ~PAGE_MASK)
1976  *              error = ret;
1977  *
1978  * This function "knows" that -ENOMEM has the bits set.
1979  */
1980 #ifndef HAVE_ARCH_UNMAPPED_AREA
1981 unsigned long
1982 arch_get_unmapped_area(struct file *filp, unsigned long addr,
1983                 unsigned long len, unsigned long pgoff, unsigned long flags)
1984 {
1985         struct mm_struct *mm = current->mm;
1986         struct vm_area_struct *vma, *prev;
1987         struct vm_unmapped_area_info info;
1988
1989         if (len > TASK_SIZE - mmap_min_addr)
1990                 return -ENOMEM;
1991
1992         if (flags & MAP_FIXED)
1993                 return addr;
1994
1995         if (addr) {
1996                 addr = PAGE_ALIGN(addr);
1997                 vma = find_vma_prev(mm, addr, &prev);
1998                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
1999                     (!vma || addr + len <= vm_start_gap(vma)) &&
2000                     (!prev || addr >= vm_end_gap(prev)))
2001                         return addr;
2002         }
2003
2004         info.flags = 0;
2005         info.length = len;
2006         info.low_limit = mm->mmap_base;
2007         info.high_limit = TASK_SIZE;
2008         info.align_mask = 0;
2009         return vm_unmapped_area(&info);
2010 }
2011 #endif
2012
2013 /*
2014  * This mmap-allocator allocates new areas top-down from below the
2015  * stack's low limit (the base):
2016  */
2017 #ifndef HAVE_ARCH_UNMAPPED_AREA_TOPDOWN
2018 unsigned long
2019 arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
2020                           const unsigned long len, const unsigned long pgoff,
2021                           const unsigned long flags)
2022 {
2023         struct vm_area_struct *vma, *prev;
2024         struct mm_struct *mm = current->mm;
2025         unsigned long addr = addr0;
2026         struct vm_unmapped_area_info info;
2027
2028         /* requested length too big for entire address space */
2029         if (len > TASK_SIZE - mmap_min_addr)
2030                 return -ENOMEM;
2031
2032         if (flags & MAP_FIXED)
2033                 return addr;
2034
2035         /* requesting a specific address */
2036         if (addr) {
2037                 addr = PAGE_ALIGN(addr);
2038                 vma = find_vma_prev(mm, addr, &prev);
2039                 if (TASK_SIZE - len >= addr && addr >= mmap_min_addr &&
2040                                 (!vma || addr + len <= vm_start_gap(vma)) &&
2041                                 (!prev || addr >= vm_end_gap(prev)))
2042                         return addr;
2043         }
2044
2045         info.flags = VM_UNMAPPED_AREA_TOPDOWN;
2046         info.length = len;
2047         info.low_limit = max(PAGE_SIZE, mmap_min_addr);
2048         info.high_limit = mm->mmap_base;
2049         info.align_mask = 0;
2050         addr = vm_unmapped_area(&info);
2051
2052         /*
2053          * A failed mmap() very likely causes application failure,
2054          * so fall back to the bottom-up function here. This scenario
2055          * can happen with large stack limits and large mmap()
2056          * allocations.
2057          */
2058         if (offset_in_page(addr)) {
2059                 VM_BUG_ON(addr != -ENOMEM);
2060                 info.flags = 0;
2061                 info.low_limit = TASK_UNMAPPED_BASE;
2062                 info.high_limit = TASK_SIZE;
2063                 addr = vm_unmapped_area(&info);
2064         }
2065
2066         return addr;
2067 }
2068 #endif
2069
2070 unsigned long
2071 get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
2072                 unsigned long pgoff, unsigned long flags)
2073 {
2074         unsigned long (*get_area)(struct file *, unsigned long,
2075                                   unsigned long, unsigned long, unsigned long);
2076
2077         unsigned long error = arch_mmap_check(addr, len, flags);
2078         if (error)
2079                 return error;
2080
2081         /* Careful about overflows.. */
2082         if (len > TASK_SIZE)
2083                 return -ENOMEM;
2084
2085         get_area = current->mm->get_unmapped_area;
2086         if (file) {
2087                 if (file->f_op->get_unmapped_area)
2088                         get_area = file->f_op->get_unmapped_area;
2089         } else if (flags & MAP_SHARED) {
2090                 /*
2091                  * mmap_region() will call shmem_zero_setup() to create a file,
2092                  * so use shmem's get_unmapped_area in case it can be huge.
2093                  * do_mmap_pgoff() will clear pgoff, so match alignment.
2094                  */
2095                 pgoff = 0;
2096                 get_area = shmem_get_unmapped_area;
2097         }
2098
2099         addr = get_area(file, addr, len, pgoff, flags);
2100         if (IS_ERR_VALUE(addr))
2101                 return addr;
2102
2103         if (addr > TASK_SIZE - len)
2104                 return -ENOMEM;
2105         if (offset_in_page(addr))
2106                 return -EINVAL;
2107
2108         error = security_mmap_addr(addr);
2109         return error ? error : addr;
2110 }
2111
2112 EXPORT_SYMBOL(get_unmapped_area);
2113
2114 /* Look up the first VMA which satisfies  addr < vm_end,  NULL if none. */
2115 struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
2116 {
2117         struct rb_node *rb_node;
2118         struct vm_area_struct *vma;
2119
2120         /* Check the cache first. */
2121         vma = vmacache_find(mm, addr);
2122         if (likely(vma))
2123                 return vma;
2124
2125         rb_node = mm->mm_rb.rb_node;
2126
2127         while (rb_node) {
2128                 struct vm_area_struct *tmp;
2129
2130                 tmp = rb_entry(rb_node, struct vm_area_struct, vm_rb);
2131
2132                 if (tmp->vm_end > addr) {
2133                         vma = tmp;
2134                         if (tmp->vm_start <= addr)
2135                                 break;
2136                         rb_node = rb_node->rb_left;
2137                 } else
2138                         rb_node = rb_node->rb_right;
2139         }
2140
2141         if (vma)
2142                 vmacache_update(addr, vma);
2143         return vma;
2144 }
2145
2146 EXPORT_SYMBOL(find_vma);
2147
2148 /*
2149  * Same as find_vma, but also return a pointer to the previous VMA in *pprev.
2150  */
2151 struct vm_area_struct *
2152 find_vma_prev(struct mm_struct *mm, unsigned long addr,
2153                         struct vm_area_struct **pprev)
2154 {
2155         struct vm_area_struct *vma;
2156
2157         vma = find_vma(mm, addr);
2158         if (vma) {
2159                 *pprev = vma->vm_prev;
2160         } else {
2161                 struct rb_node *rb_node = mm->mm_rb.rb_node;
2162                 *pprev = NULL;
2163                 while (rb_node) {
2164                         *pprev = rb_entry(rb_node, struct vm_area_struct, vm_rb);
2165                         rb_node = rb_node->rb_right;
2166                 }
2167         }
2168         return vma;
2169 }
2170
2171 /*
2172  * Verify that the stack growth is acceptable and
2173  * update accounting. This is shared with both the
2174  * grow-up and grow-down cases.
2175  */
2176 static int acct_stack_growth(struct vm_area_struct *vma,
2177                              unsigned long size, unsigned long grow)
2178 {
2179         struct mm_struct *mm = vma->vm_mm;
2180         unsigned long new_start;
2181
2182         /* address space limit tests */
2183         if (!may_expand_vm(mm, vma->vm_flags, grow))
2184                 return -ENOMEM;
2185
2186         /* Stack limit test */
2187         if (size > rlimit(RLIMIT_STACK))
2188                 return -ENOMEM;
2189
2190         /* mlock limit tests */
2191         if (vma->vm_flags & VM_LOCKED) {
2192                 unsigned long locked;
2193                 unsigned long limit;
2194                 locked = mm->locked_vm + grow;
2195                 limit = rlimit(RLIMIT_MEMLOCK);
2196                 limit >>= PAGE_SHIFT;
2197                 if (locked > limit && !capable(CAP_IPC_LOCK))
2198                         return -ENOMEM;
2199         }
2200
2201         /* Check to ensure the stack will not grow into a hugetlb-only region */
2202         new_start = (vma->vm_flags & VM_GROWSUP) ? vma->vm_start :
2203                         vma->vm_end - size;
2204         if (is_hugepage_only_range(vma->vm_mm, new_start, size))
2205                 return -EFAULT;
2206
2207         /*
2208          * Overcommit..  This must be the final test, as it will
2209          * update security statistics.
2210          */
2211         if (security_vm_enough_memory_mm(mm, grow))
2212                 return -ENOMEM;
2213
2214         return 0;
2215 }
2216
2217 #if defined(CONFIG_STACK_GROWSUP) || defined(CONFIG_IA64)
2218 /*
2219  * PA-RISC uses this for its stack; IA64 for its Register Backing Store.
2220  * vma is the last one with address > vma->vm_end.  Have to extend vma.
2221  */
2222 int expand_upwards(struct vm_area_struct *vma, unsigned long address)
2223 {
2224         struct mm_struct *mm = vma->vm_mm;
2225         struct vm_area_struct *next;
2226         unsigned long gap_addr;
2227         int error = 0;
2228
2229         if (!(vma->vm_flags & VM_GROWSUP))
2230                 return -EFAULT;
2231
2232         /* Guard against exceeding limits of the address space. */
2233         address &= PAGE_MASK;
2234         if (address >= (TASK_SIZE & PAGE_MASK))
2235                 return -ENOMEM;
2236         address += PAGE_SIZE;
2237
2238         /* Enforce stack_guard_gap */
2239         gap_addr = address + stack_guard_gap;
2240
2241         /* Guard against overflow */
2242         if (gap_addr < address || gap_addr > TASK_SIZE)
2243                 gap_addr = TASK_SIZE;
2244
2245         next = vma->vm_next;
2246         if (next && next->vm_start < gap_addr &&
2247                         (next->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
2248                 if (!(next->vm_flags & VM_GROWSUP))
2249                         return -ENOMEM;
2250                 /* Check that both stack segments have the same anon_vma? */
2251         }
2252
2253         /* We must make sure the anon_vma is allocated. */
2254         if (unlikely(anon_vma_prepare(vma)))
2255                 return -ENOMEM;
2256
2257         /*
2258          * vma->vm_start/vm_end cannot change under us because the caller
2259          * is required to hold the mmap_sem in read mode.  We need the
2260          * anon_vma lock to serialize against concurrent expand_stacks.
2261          */
2262         anon_vma_lock_write(vma->anon_vma);
2263
2264         /* Somebody else might have raced and expanded it already */
2265         if (address > vma->vm_end) {
2266                 unsigned long size, grow;
2267
2268                 size = address - vma->vm_start;
2269                 grow = (address - vma->vm_end) >> PAGE_SHIFT;
2270
2271                 error = -ENOMEM;
2272                 if (vma->vm_pgoff + (size >> PAGE_SHIFT) >= vma->vm_pgoff) {
2273                         error = acct_stack_growth(vma, size, grow);
2274                         if (!error) {
2275                                 /*
2276                                  * vma_gap_update() doesn't support concurrent
2277                                  * updates, but we only hold a shared mmap_sem
2278                                  * lock here, so we need to protect against
2279                                  * concurrent vma expansions.
2280                                  * anon_vma_lock_write() doesn't help here, as
2281                                  * we don't guarantee that all growable vmas
2282                                  * in a mm share the same root anon vma.
2283                                  * So, we reuse mm->page_table_lock to guard
2284                                  * against concurrent vma expansions.
2285                                  */
2286                                 spin_lock(&mm->page_table_lock);
2287                                 if (vma->vm_flags & VM_LOCKED)
2288                                         mm->locked_vm += grow;
2289                                 vm_stat_account(mm, vma->vm_flags, grow);
2290                                 anon_vma_interval_tree_pre_update_vma(vma);
2291                                 vma->vm_end = address;
2292                                 anon_vma_interval_tree_post_update_vma(vma);
2293                                 if (vma->vm_next)
2294                                         vma_gap_update(vma->vm_next);
2295                                 else
2296                                         mm->highest_vm_end = vm_end_gap(vma);
2297                                 spin_unlock(&mm->page_table_lock);
2298
2299                                 perf_event_mmap(vma);
2300                         }
2301                 }
2302         }
2303         anon_vma_unlock_write(vma->anon_vma);
2304         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2305         validate_mm(mm);
2306         return error;
2307 }
2308 #endif /* CONFIG_STACK_GROWSUP || CONFIG_IA64 */
2309
2310 /*
2311  * vma is the first one with address < vma->vm_start.  Have to extend vma.
2312  */
2313 int expand_downwards(struct vm_area_struct *vma,
2314                                    unsigned long address)
2315 {
2316         struct mm_struct *mm = vma->vm_mm;
2317         struct vm_area_struct *prev;
2318         int error;
2319
2320         address &= PAGE_MASK;
2321         error = security_mmap_addr(address);
2322         if (error)
2323                 return error;
2324
2325         /* Enforce stack_guard_gap */
2326         prev = vma->vm_prev;
2327         /* Check that both stack segments have the same anon_vma? */
2328         if (prev && !(prev->vm_flags & VM_GROWSDOWN) &&
2329                         (prev->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
2330                 if (address - prev->vm_end < stack_guard_gap)
2331                         return -ENOMEM;
2332         }
2333
2334         /* We must make sure the anon_vma is allocated. */
2335         if (unlikely(anon_vma_prepare(vma)))
2336                 return -ENOMEM;
2337
2338         /*
2339          * vma->vm_start/vm_end cannot change under us because the caller
2340          * is required to hold the mmap_sem in read mode.  We need the
2341          * anon_vma lock to serialize against concurrent expand_stacks.
2342          */
2343         anon_vma_lock_write(vma->anon_vma);
2344
2345         /* Somebody else might have raced and expanded it already */
2346         if (address < vma->vm_start) {
2347                 unsigned long size, grow;
2348
2349                 size = vma->vm_end - address;
2350                 grow = (vma->vm_start - address) >> PAGE_SHIFT;
2351
2352                 error = -ENOMEM;
2353                 if (grow <= vma->vm_pgoff) {
2354                         error = acct_stack_growth(vma, size, grow);
2355                         if (!error) {
2356                                 /*
2357                                  * vma_gap_update() doesn't support concurrent
2358                                  * updates, but we only hold a shared mmap_sem
2359                                  * lock here, so we need to protect against
2360                                  * concurrent vma expansions.
2361                                  * anon_vma_lock_write() doesn't help here, as
2362                                  * we don't guarantee that all growable vmas
2363                                  * in a mm share the same root anon vma.
2364                                  * So, we reuse mm->page_table_lock to guard
2365                                  * against concurrent vma expansions.
2366                                  */
2367                                 spin_lock(&mm->page_table_lock);
2368                                 if (vma->vm_flags & VM_LOCKED)
2369                                         mm->locked_vm += grow;
2370                                 vm_stat_account(mm, vma->vm_flags, grow);
2371                                 anon_vma_interval_tree_pre_update_vma(vma);
2372                                 vma->vm_start = address;
2373                                 vma->vm_pgoff -= grow;
2374                                 anon_vma_interval_tree_post_update_vma(vma);
2375                                 vma_gap_update(vma);
2376                                 spin_unlock(&mm->page_table_lock);
2377
2378                                 perf_event_mmap(vma);
2379                         }
2380                 }
2381         }
2382         anon_vma_unlock_write(vma->anon_vma);
2383         khugepaged_enter_vma_merge(vma, vma->vm_flags);
2384         validate_mm(mm);
2385         return error;
2386 }
2387
2388 /* enforced gap between the expanding stack and other mappings. */
2389 unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT;
2390
2391 static int __init cmdline_parse_stack_guard_gap(char *p)
2392 {
2393         unsigned long val;
2394         char *endptr;
2395
2396         val = simple_strtoul(p, &endptr, 10);
2397         if (!*endptr)
2398                 stack_guard_gap = val << PAGE_SHIFT;
2399
2400         return 0;
2401 }
2402 __setup("stack_guard_gap=", cmdline_parse_stack_guard_gap);
2403
2404 #ifdef CONFIG_STACK_GROWSUP
2405 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2406 {
2407         return expand_upwards(vma, address);
2408 }
2409
2410 struct vm_area_struct *
2411 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2412 {
2413         struct vm_area_struct *vma, *prev;
2414
2415         addr &= PAGE_MASK;
2416         vma = find_vma_prev(mm, addr, &prev);
2417         if (vma && (vma->vm_start <= addr))
2418                 return vma;
2419         if (!prev || expand_stack(prev, addr))
2420                 return NULL;
2421         if (prev->vm_flags & VM_LOCKED)
2422                 populate_vma_page_range(prev, addr, prev->vm_end, NULL);
2423         return prev;
2424 }
2425 #else
2426 int expand_stack(struct vm_area_struct *vma, unsigned long address)
2427 {
2428         return expand_downwards(vma, address);
2429 }
2430
2431 struct vm_area_struct *
2432 find_extend_vma(struct mm_struct *mm, unsigned long addr)
2433 {
2434         struct vm_area_struct *vma;
2435         unsigned long start;
2436
2437         addr &= PAGE_MASK;
2438         vma = find_vma(mm, addr);
2439         if (!vma)
2440                 return NULL;
2441         if (vma->vm_start <= addr)
2442                 return vma;
2443         if (!(vma->vm_flags & VM_GROWSDOWN))
2444                 return NULL;
2445         start = vma->vm_start;
2446         if (expand_stack(vma, addr))
2447                 return NULL;
2448         if (vma->vm_flags & VM_LOCKED)
2449                 populate_vma_page_range(vma, addr, start, NULL);
2450         return vma;
2451 }
2452 #endif
2453
2454 EXPORT_SYMBOL_GPL(find_extend_vma);
2455
2456 /*
2457  * Ok - we have the memory areas we should free on the vma list,
2458  * so release them, and do the vma updates.
2459  *
2460  * Called with the mm semaphore held.
2461  */
2462 static void remove_vma_list(struct mm_struct *mm, struct vm_area_struct *vma)
2463 {
2464         unsigned long nr_accounted = 0;
2465
2466         /* Update high watermark before we lower total_vm */
2467         update_hiwater_vm(mm);
2468         do {
2469                 long nrpages = vma_pages(vma);
2470
2471                 if (vma->vm_flags & VM_ACCOUNT)
2472                         nr_accounted += nrpages;
2473                 vm_stat_account(mm, vma->vm_flags, -nrpages);
2474                 vma = remove_vma(vma);
2475         } while (vma);
2476         vm_unacct_memory(nr_accounted);
2477         validate_mm(mm);
2478 }
2479
2480 /*
2481  * Get rid of page table information in the indicated region.
2482  *
2483  * Called with the mm semaphore held.
2484  */
2485 static void unmap_region(struct mm_struct *mm,
2486                 struct vm_area_struct *vma, struct vm_area_struct *prev,
2487                 unsigned long start, unsigned long end)
2488 {
2489         struct vm_area_struct *next = prev ? prev->vm_next : mm->mmap;
2490         struct mmu_gather tlb;
2491
2492         lru_add_drain();
2493         tlb_gather_mmu(&tlb, mm, start, end);
2494         update_hiwater_rss(mm);
2495         unmap_vmas(&tlb, vma, start, end);
2496         free_pgtables(&tlb, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
2497                                  next ? next->vm_start : USER_PGTABLES_CEILING);
2498         tlb_finish_mmu(&tlb, start, end);
2499 }
2500
2501 /*
2502  * Create a list of vma's touched by the unmap, removing them from the mm's
2503  * vma list as we go..
2504  */
2505 static void
2506 detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
2507         struct vm_area_struct *prev, unsigned long end)
2508 {
2509         struct vm_area_struct **insertion_point;
2510         struct vm_area_struct *tail_vma = NULL;
2511
2512         insertion_point = (prev ? &prev->vm_next : &mm->mmap);
2513         vma->vm_prev = NULL;
2514         do {
2515                 vma_rb_erase(vma, &mm->mm_rb);
2516                 mm->map_count--;
2517                 tail_vma = vma;
2518                 vma = vma->vm_next;
2519         } while (vma && vma->vm_start < end);
2520         *insertion_point = vma;
2521         if (vma) {
2522                 vma->vm_prev = prev;
2523                 vma_gap_update(vma);
2524         } else
2525                 mm->highest_vm_end = prev ? vm_end_gap(prev) : 0;
2526         tail_vma->vm_next = NULL;
2527
2528         /* Kill the cache */
2529         vmacache_invalidate(mm);
2530 }
2531
2532 /*
2533  * __split_vma() bypasses sysctl_max_map_count checking.  We use this where it
2534  * has already been checked or doesn't make sense to fail.
2535  */
2536 int __split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2537                 unsigned long addr, int new_below)
2538 {
2539         struct vm_area_struct *new;
2540         int err;
2541
2542         if (is_vm_hugetlb_page(vma) && (addr &
2543                                         ~(huge_page_mask(hstate_vma(vma)))))
2544                 return -EINVAL;
2545
2546         new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
2547         if (!new)
2548                 return -ENOMEM;
2549
2550         /* most fields are the same, copy all, and then fixup */
2551         *new = *vma;
2552
2553         INIT_LIST_HEAD(&new->anon_vma_chain);
2554
2555         if (new_below)
2556                 new->vm_end = addr;
2557         else {
2558                 new->vm_start = addr;
2559                 new->vm_pgoff += ((addr - vma->vm_start) >> PAGE_SHIFT);
2560         }
2561
2562         err = vma_dup_policy(vma, new);
2563         if (err)
2564                 goto out_free_vma;
2565
2566         err = anon_vma_clone(new, vma);
2567         if (err)
2568                 goto out_free_mpol;
2569
2570         if (new->vm_file)
2571                 get_file(new->vm_file);
2572
2573         if (new->vm_ops && new->vm_ops->open)
2574                 new->vm_ops->open(new);
2575
2576         if (new_below)
2577                 err = vma_adjust(vma, addr, vma->vm_end, vma->vm_pgoff +
2578                         ((addr - new->vm_start) >> PAGE_SHIFT), new);
2579         else
2580                 err = vma_adjust(vma, vma->vm_start, addr, vma->vm_pgoff, new);
2581
2582         /* Success. */
2583         if (!err)
2584                 return 0;
2585
2586         /* Clean everything up if vma_adjust failed. */
2587         if (new->vm_ops && new->vm_ops->close)
2588                 new->vm_ops->close(new);
2589         if (new->vm_file)
2590                 fput(new->vm_file);
2591         unlink_anon_vmas(new);
2592  out_free_mpol:
2593         mpol_put(vma_policy(new));
2594  out_free_vma:
2595         kmem_cache_free(vm_area_cachep, new);
2596         return err;
2597 }
2598
2599 /*
2600  * Split a vma into two pieces at address 'addr', a new vma is allocated
2601  * either for the first part or the tail.
2602  */
2603 int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
2604               unsigned long addr, int new_below)
2605 {
2606         if (mm->map_count >= sysctl_max_map_count)
2607                 return -ENOMEM;
2608
2609         return __split_vma(mm, vma, addr, new_below);
2610 }
2611
2612 /* Munmap is split into 2 main parts -- this part which finds
2613  * what needs doing, and the areas themselves, which do the
2614  * work.  This now handles partial unmappings.
2615  * Jeremy Fitzhardinge <jeremy@goop.org>
2616  */
2617 int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
2618               struct list_head *uf)
2619 {
2620         unsigned long end;
2621         struct vm_area_struct *vma, *prev, *last;
2622
2623         if ((offset_in_page(start)) || start > TASK_SIZE || len > TASK_SIZE-start)
2624                 return -EINVAL;
2625
2626         len = PAGE_ALIGN(len);
2627         if (len == 0)
2628                 return -EINVAL;
2629
2630         /* Find the first overlapping VMA */
2631         vma = find_vma(mm, start);
2632         if (!vma)
2633                 return 0;
2634         prev = vma->vm_prev;
2635         /* we have  start < vma->vm_end  */
2636
2637         /* if it doesn't overlap, we have nothing.. */
2638         end = start + len;
2639         if (vma->vm_start >= end)
2640                 return 0;
2641
2642         if (uf) {
2643                 int error = userfaultfd_unmap_prep(vma, start, end, uf);
2644
2645                 if (error)
2646                         return error;
2647         }
2648
2649         /*
2650          * If we need to split any vma, do it now to save pain later.
2651          *
2652          * Note: mremap's move_vma VM_ACCOUNT handling assumes a partially
2653          * unmapped vm_area_struct will remain in use: so lower split_vma
2654          * places tmp vma above, and higher split_vma places tmp vma below.
2655          */
2656         if (start > vma->vm_start) {
2657                 int error;
2658
2659                 /*
2660                  * Make sure that map_count on return from munmap() will
2661                  * not exceed its limit; but let map_count go just above
2662                  * its limit temporarily, to help free resources as expected.
2663                  */
2664                 if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count)
2665                         return -ENOMEM;
2666
2667                 error = __split_vma(mm, vma, start, 0);
2668                 if (error)
2669                         return error;
2670                 prev = vma;
2671         }
2672
2673         /* Does it split the last one? */
2674         last = find_vma(mm, end);
2675         if (last && end > last->vm_start) {
2676                 int error = __split_vma(mm, last, end, 1);
2677                 if (error)
2678                         return error;
2679         }
2680         vma = prev ? prev->vm_next : mm->mmap;
2681
2682         /*
2683          * unlock any mlock()ed ranges before detaching vmas
2684          */
2685         if (mm->locked_vm) {
2686                 struct vm_area_struct *tmp = vma;
2687                 while (tmp && tmp->vm_start < end) {
2688                         if (tmp->vm_flags & VM_LOCKED) {
2689                                 mm->locked_vm -= vma_pages(tmp);
2690                                 munlock_vma_pages_all(tmp);
2691                         }
2692                         tmp = tmp->vm_next;
2693                 }
2694         }
2695
2696         /*
2697          * Remove the vma's, and unmap the actual pages
2698          */
2699         detach_vmas_to_be_unmapped(mm, vma, prev, end);
2700         unmap_region(mm, vma, prev, start, end);
2701
2702         arch_unmap(mm, vma, start, end);
2703
2704         /* Fix up all other VM information */
2705         remove_vma_list(mm, vma);
2706
2707         return 0;
2708 }
2709
2710 int vm_munmap(unsigned long start, size_t len)
2711 {
2712         int ret;
2713         struct mm_struct *mm = current->mm;
2714         LIST_HEAD(uf);
2715
2716         if (down_write_killable(&mm->mmap_sem))
2717                 return -EINTR;
2718
2719         ret = do_munmap(mm, start, len, &uf);
2720         up_write(&mm->mmap_sem);
2721         userfaultfd_unmap_complete(mm, &uf);
2722         return ret;
2723 }
2724 EXPORT_SYMBOL(vm_munmap);
2725
2726 SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
2727 {
2728         profile_munmap(addr);
2729         return vm_munmap(addr, len);
2730 }
2731
2732
2733 /*
2734  * Emulation of deprecated remap_file_pages() syscall.
2735  */
2736 SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
2737                 unsigned long, prot, unsigned long, pgoff, unsigned long, flags)
2738 {
2739
2740         struct mm_struct *mm = current->mm;
2741         struct vm_area_struct *vma;
2742         unsigned long populate = 0;
2743         unsigned long ret = -EINVAL;
2744         struct file *file;
2745
2746         pr_warn_once("%s (%d) uses deprecated remap_file_pages() syscall. See Documentation/vm/remap_file_pages.txt.\n",
2747                      current->comm, current->pid);
2748
2749         if (prot)
2750                 return ret;
2751         start = start & PAGE_MASK;
2752         size = size & PAGE_MASK;
2753
2754         if (start + size <= start)
2755                 return ret;
2756
2757         /* Does pgoff wrap? */
2758         if (pgoff + (size >> PAGE_SHIFT) < pgoff)
2759                 return ret;
2760
2761         if (down_write_killable(&mm->mmap_sem))
2762                 return -EINTR;
2763
2764         vma = find_vma(mm, start);
2765
2766         if (!vma || !(vma->vm_flags & VM_SHARED))
2767                 goto out;
2768
2769         if (start < vma->vm_start)
2770                 goto out;
2771
2772         if (start + size > vma->vm_end) {
2773                 struct vm_area_struct *next;
2774
2775                 for (next = vma->vm_next; next; next = next->vm_next) {
2776                         /* hole between vmas ? */
2777                         if (next->vm_start != next->vm_prev->vm_end)
2778                                 goto out;
2779
2780                         if (next->vm_file != vma->vm_file)
2781                                 goto out;
2782
2783                         if (next->vm_flags != vma->vm_flags)
2784                                 goto out;
2785
2786                         if (start + size <= next->vm_end)
2787                                 break;
2788                 }
2789
2790                 if (!next)
2791                         goto out;
2792         }
2793
2794         prot |= vma->vm_flags & VM_READ ? PROT_READ : 0;
2795         prot |= vma->vm_flags & VM_WRITE ? PROT_WRITE : 0;
2796         prot |= vma->vm_flags & VM_EXEC ? PROT_EXEC : 0;
2797
2798         flags &= MAP_NONBLOCK;
2799         flags |= MAP_SHARED | MAP_FIXED | MAP_POPULATE;
2800         if (vma->vm_flags & VM_LOCKED) {
2801                 struct vm_area_struct *tmp;
2802                 flags |= MAP_LOCKED;
2803
2804                 /* drop PG_Mlocked flag for over-mapped range */
2805                 for (tmp = vma; tmp->vm_start >= start + size;
2806                                 tmp = tmp->vm_next) {
2807                         /*
2808                          * Split pmd and munlock page on the border
2809                          * of the range.
2810                          */
2811                         vma_adjust_trans_huge(tmp, start, start + size, 0);
2812
2813                         munlock_vma_pages_range(tmp,
2814                                         max(tmp->vm_start, start),
2815                                         min(tmp->vm_end, start + size));
2816                 }
2817         }
2818
2819         file = get_file(vma->vm_file);
2820         ret = do_mmap_pgoff(vma->vm_file, start, size,
2821                         prot, flags, pgoff, &populate, NULL);
2822         fput(file);
2823 out:
2824         up_write(&mm->mmap_sem);
2825         if (populate)
2826                 mm_populate(ret, populate);
2827         if (!IS_ERR_VALUE(ret))
2828                 ret = 0;
2829         return ret;
2830 }
2831
2832 static inline void verify_mm_writelocked(struct mm_struct *mm)
2833 {
2834 #ifdef CONFIG_DEBUG_VM
2835         if (unlikely(down_read_trylock(&mm->mmap_sem))) {
2836                 WARN_ON(1);
2837                 up_read(&mm->mmap_sem);
2838         }
2839 #endif
2840 }
2841
2842 /*
2843  *  this is really a simplified "do_mmap".  it only handles
2844  *  anonymous maps.  eventually we may be able to do some
2845  *  brk-specific accounting here.
2846  */
2847 static int do_brk_flags(unsigned long addr, unsigned long request, unsigned long flags, struct list_head *uf)
2848 {
2849         struct mm_struct *mm = current->mm;
2850         struct vm_area_struct *vma, *prev;
2851         unsigned long len;
2852         struct rb_node **rb_link, *rb_parent;
2853         pgoff_t pgoff = addr >> PAGE_SHIFT;
2854         int error;
2855
2856         len = PAGE_ALIGN(request);
2857         if (len < request)
2858                 return -ENOMEM;
2859         if (!len)
2860                 return 0;
2861
2862         /* Until we need other flags, refuse anything except VM_EXEC. */
2863         if ((flags & (~VM_EXEC)) != 0)
2864                 return -EINVAL;
2865         flags |= VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
2866
2867         error = get_unmapped_area(NULL, addr, len, 0, MAP_FIXED);
2868         if (offset_in_page(error))
2869                 return error;
2870
2871         error = mlock_future_check(mm, mm->def_flags, len);
2872         if (error)
2873                 return error;
2874
2875         /*
2876          * mm->mmap_sem is required to protect against another thread
2877          * changing the mappings in case we sleep.
2878          */
2879         verify_mm_writelocked(mm);
2880
2881         /*
2882          * Clear old maps.  this also does some error checking for us
2883          */
2884         while (find_vma_links(mm, addr, addr + len, &prev, &rb_link,
2885                               &rb_parent)) {
2886                 if (do_munmap(mm, addr, len, uf))
2887                         return -ENOMEM;
2888         }
2889
2890         /* Check against address space limits *after* clearing old maps... */
2891         if (!may_expand_vm(mm, flags, len >> PAGE_SHIFT))
2892                 return -ENOMEM;
2893
2894         if (mm->map_count > sysctl_max_map_count)
2895                 return -ENOMEM;
2896
2897         if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
2898                 return -ENOMEM;
2899
2900         /* Can we just expand an old private anonymous mapping? */
2901         vma = vma_merge(mm, prev, addr, addr + len, flags,
2902                         NULL, NULL, pgoff, NULL, NULL_VM_UFFD_CTX);
2903         if (vma)
2904                 goto out;
2905
2906         /*
2907          * create a vma struct for an anonymous mapping
2908          */
2909         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
2910         if (!vma) {
2911                 vm_unacct_memory(len >> PAGE_SHIFT);
2912                 return -ENOMEM;
2913         }
2914
2915         INIT_LIST_HEAD(&vma->anon_vma_chain);
2916         vma->vm_mm = mm;
2917         vma->vm_start = addr;
2918         vma->vm_end = addr + len;
2919         vma->vm_pgoff = pgoff;
2920         vma->vm_flags = flags;
2921         vma->vm_page_prot = vm_get_page_prot(flags);
2922         vma_link(mm, vma, prev, rb_link, rb_parent);
2923 out:
2924         perf_event_mmap(vma);
2925         mm->total_vm += len >> PAGE_SHIFT;
2926         mm->data_vm += len >> PAGE_SHIFT;
2927         if (flags & VM_LOCKED)
2928                 mm->locked_vm += (len >> PAGE_SHIFT);
2929         vma->vm_flags |= VM_SOFTDIRTY;
2930         return 0;
2931 }
2932
2933 static int do_brk(unsigned long addr, unsigned long len, struct list_head *uf)
2934 {
2935         return do_brk_flags(addr, len, 0, uf);
2936 }
2937
2938 int vm_brk_flags(unsigned long addr, unsigned long len, unsigned long flags)
2939 {
2940         struct mm_struct *mm = current->mm;
2941         int ret;
2942         bool populate;
2943         LIST_HEAD(uf);
2944
2945         if (down_write_killable(&mm->mmap_sem))
2946                 return -EINTR;
2947
2948         ret = do_brk_flags(addr, len, flags, &uf);
2949         populate = ((mm->def_flags & VM_LOCKED) != 0);
2950         up_write(&mm->mmap_sem);
2951         userfaultfd_unmap_complete(mm, &uf);
2952         if (populate && !ret)
2953                 mm_populate(addr, len);
2954         return ret;
2955 }
2956 EXPORT_SYMBOL(vm_brk_flags);
2957
2958 int vm_brk(unsigned long addr, unsigned long len)
2959 {
2960         return vm_brk_flags(addr, len, 0);
2961 }
2962 EXPORT_SYMBOL(vm_brk);
2963
2964 /* Release all mmaps. */
2965 void exit_mmap(struct mm_struct *mm)
2966 {
2967         struct mmu_gather tlb;
2968         struct vm_area_struct *vma;
2969         unsigned long nr_accounted = 0;
2970
2971         /* mm's last user has gone, and its about to be pulled down */
2972         mmu_notifier_release(mm);
2973
2974         if (mm->locked_vm) {
2975                 vma = mm->mmap;
2976                 while (vma) {
2977                         if (vma->vm_flags & VM_LOCKED)
2978                                 munlock_vma_pages_all(vma);
2979                         vma = vma->vm_next;
2980                 }
2981         }
2982
2983         arch_exit_mmap(mm);
2984
2985         vma = mm->mmap;
2986         if (!vma)       /* Can happen if dup_mmap() received an OOM */
2987                 return;
2988
2989         lru_add_drain();
2990         flush_cache_mm(mm);
2991         tlb_gather_mmu(&tlb, mm, 0, -1);
2992         /* update_hiwater_rss(mm) here? but nobody should be looking */
2993         /* Use -1 here to ensure all VMAs in the mm are unmapped */
2994         unmap_vmas(&tlb, vma, 0, -1);
2995
2996         free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, USER_PGTABLES_CEILING);
2997         tlb_finish_mmu(&tlb, 0, -1);
2998
2999         /*
3000          * Walk the list again, actually closing and freeing it,
3001          * with preemption enabled, without holding any MM locks.
3002          */
3003         while (vma) {
3004                 if (vma->vm_flags & VM_ACCOUNT)
3005                         nr_accounted += vma_pages(vma);
3006                 vma = remove_vma(vma);
3007         }
3008         vm_unacct_memory(nr_accounted);
3009 }
3010
3011 /* Insert vm structure into process list sorted by address
3012  * and into the inode's i_mmap tree.  If vm_file is non-NULL
3013  * then i_mmap_rwsem is taken here.
3014  */
3015 int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
3016 {
3017         struct vm_area_struct *prev;
3018         struct rb_node **rb_link, *rb_parent;
3019
3020         if (find_vma_links(mm, vma->vm_start, vma->vm_end,
3021                            &prev, &rb_link, &rb_parent))
3022                 return -ENOMEM;
3023         if ((vma->vm_flags & VM_ACCOUNT) &&
3024              security_vm_enough_memory_mm(mm, vma_pages(vma)))
3025                 return -ENOMEM;
3026
3027         /*
3028          * The vm_pgoff of a purely anonymous vma should be irrelevant
3029          * until its first write fault, when page's anon_vma and index
3030          * are set.  But now set the vm_pgoff it will almost certainly
3031          * end up with (unless mremap moves it elsewhere before that
3032          * first wfault), so /proc/pid/maps tells a consistent story.
3033          *
3034          * By setting it to reflect the virtual start address of the
3035          * vma, merges and splits can happen in a seamless way, just
3036          * using the existing file pgoff checks and manipulations.
3037          * Similarly in do_mmap_pgoff and in do_brk.
3038          */
3039         if (vma_is_anonymous(vma)) {
3040                 BUG_ON(vma->anon_vma);
3041                 vma->vm_pgoff = vma->vm_start >> PAGE_SHIFT;
3042         }
3043
3044         vma_link(mm, vma, prev, rb_link, rb_parent);
3045         return 0;
3046 }
3047
3048 /*
3049  * Copy the vma structure to a new location in the same mm,
3050  * prior to moving page table entries, to effect an mremap move.
3051  */
3052 struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
3053         unsigned long addr, unsigned long len, pgoff_t pgoff,
3054         bool *need_rmap_locks)
3055 {
3056         struct vm_area_struct *vma = *vmap;
3057         unsigned long vma_start = vma->vm_start;
3058         struct mm_struct *mm = vma->vm_mm;
3059         struct vm_area_struct *new_vma, *prev;
3060         struct rb_node **rb_link, *rb_parent;
3061         bool faulted_in_anon_vma = true;
3062
3063         /*
3064          * If anonymous vma has not yet been faulted, update new pgoff
3065          * to match new location, to increase its chance of merging.
3066          */
3067         if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
3068                 pgoff = addr >> PAGE_SHIFT;
3069                 faulted_in_anon_vma = false;
3070         }
3071
3072         if (find_vma_links(mm, addr, addr + len, &prev, &rb_link, &rb_parent))
3073                 return NULL;    /* should never get here */
3074         new_vma = vma_merge(mm, prev, addr, addr + len, vma->vm_flags,
3075                             vma->anon_vma, vma->vm_file, pgoff, vma_policy(vma),
3076                             vma->vm_userfaultfd_ctx);
3077         if (new_vma) {
3078                 /*
3079                  * Source vma may have been merged into new_vma
3080                  */
3081                 if (unlikely(vma_start >= new_vma->vm_start &&
3082                              vma_start < new_vma->vm_end)) {
3083                         /*
3084                          * The only way we can get a vma_merge with
3085                          * self during an mremap is if the vma hasn't
3086                          * been faulted in yet and we were allowed to
3087                          * reset the dst vma->vm_pgoff to the
3088                          * destination address of the mremap to allow
3089                          * the merge to happen. mremap must change the
3090                          * vm_pgoff linearity between src and dst vmas
3091                          * (in turn preventing a vma_merge) to be
3092                          * safe. It is only safe to keep the vm_pgoff
3093                          * linear if there are no pages mapped yet.
3094                          */
3095                         VM_BUG_ON_VMA(faulted_in_anon_vma, new_vma);
3096                         *vmap = vma = new_vma;
3097                 }
3098                 *need_rmap_locks = (new_vma->vm_pgoff <= vma->vm_pgoff);
3099         } else {
3100                 new_vma = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL);
3101                 if (!new_vma)
3102                         goto out;
3103                 *new_vma = *vma;
3104                 new_vma->vm_start = addr;
3105                 new_vma->vm_end = addr + len;
3106                 new_vma->vm_pgoff = pgoff;
3107                 if (vma_dup_policy(vma, new_vma))
3108                         goto out_free_vma;
3109                 INIT_LIST_HEAD(&new_vma->anon_vma_chain);
3110                 if (anon_vma_clone(new_vma, vma))
3111                         goto out_free_mempol;
3112                 if (new_vma->vm_file)
3113                         get_file(new_vma->vm_file);
3114                 if (new_vma->vm_ops && new_vma->vm_ops->open)
3115                         new_vma->vm_ops->open(new_vma);
3116                 vma_link(mm, new_vma, prev, rb_link, rb_parent);
3117                 *need_rmap_locks = false;
3118         }
3119         return new_vma;
3120
3121 out_free_mempol:
3122         mpol_put(vma_policy(new_vma));
3123 out_free_vma:
3124         kmem_cache_free(vm_area_cachep, new_vma);
3125 out:
3126         return NULL;
3127 }
3128
3129 /*
3130  * Return true if the calling process may expand its vm space by the passed
3131  * number of pages
3132  */
3133 bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
3134 {
3135         if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
3136                 return false;
3137
3138         if (is_data_mapping(flags) &&
3139             mm->data_vm + npages > rlimit(RLIMIT_DATA) >> PAGE_SHIFT) {
3140                 /* Workaround for Valgrind */
3141                 if (rlimit(RLIMIT_DATA) == 0 &&
3142                     mm->data_vm + npages <= rlimit_max(RLIMIT_DATA) >> PAGE_SHIFT)
3143                         return true;
3144                 if (!ignore_rlimit_data) {
3145                         pr_warn_once("%s (%d): VmData %lu exceed data ulimit %lu. Update limits or use boot option ignore_rlimit_data.\n",
3146                                      current->comm, current->pid,
3147                                      (mm->data_vm + npages) << PAGE_SHIFT,
3148                                      rlimit(RLIMIT_DATA));
3149                         return false;
3150                 }
3151         }
3152
3153         return true;
3154 }
3155
3156 void vm_stat_account(struct mm_struct *mm, vm_flags_t flags, long npages)
3157 {
3158         mm->total_vm += npages;
3159
3160         if (is_exec_mapping(flags))
3161                 mm->exec_vm += npages;
3162         else if (is_stack_mapping(flags))
3163                 mm->stack_vm += npages;
3164         else if (is_data_mapping(flags))
3165                 mm->data_vm += npages;
3166 }
3167
3168 static int special_mapping_fault(struct vm_fault *vmf);
3169
3170 /*
3171  * Having a close hook prevents vma merging regardless of flags.
3172  */
3173 static void special_mapping_close(struct vm_area_struct *vma)
3174 {
3175 }
3176
3177 static const char *special_mapping_name(struct vm_area_struct *vma)
3178 {
3179         return ((struct vm_special_mapping *)vma->vm_private_data)->name;
3180 }
3181
3182 static int special_mapping_mremap(struct vm_area_struct *new_vma)
3183 {
3184         struct vm_special_mapping *sm = new_vma->vm_private_data;
3185
3186         if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
3187                 return -EFAULT;
3188
3189         if (sm->mremap)
3190                 return sm->mremap(sm, new_vma);
3191
3192         return 0;
3193 }
3194
3195 static const struct vm_operations_struct special_mapping_vmops = {
3196         .close = special_mapping_close,
3197         .fault = special_mapping_fault,
3198         .mremap = special_mapping_mremap,
3199         .name = special_mapping_name,
3200 };
3201
3202 static const struct vm_operations_struct legacy_special_mapping_vmops = {
3203         .close = special_mapping_close,
3204         .fault = special_mapping_fault,
3205 };
3206
3207 static int special_mapping_fault(struct vm_fault *vmf)
3208 {
3209         struct vm_area_struct *vma = vmf->vma;
3210         pgoff_t pgoff;
3211         struct page **pages;
3212
3213         if (vma->vm_ops == &legacy_special_mapping_vmops) {
3214                 pages = vma->vm_private_data;
3215         } else {
3216                 struct vm_special_mapping *sm = vma->vm_private_data;
3217
3218                 if (sm->fault)
3219                         return sm->fault(sm, vmf->vma, vmf);
3220
3221                 pages = sm->pages;
3222         }
3223
3224         for (pgoff = vmf->pgoff; pgoff && *pages; ++pages)
3225                 pgoff--;
3226
3227         if (*pages) {
3228                 struct page *page = *pages;
3229                 get_page(page);
3230                 vmf->page = page;
3231                 return 0;
3232         }
3233
3234         return VM_FAULT_SIGBUS;
3235 }
3236
3237 static struct vm_area_struct *__install_special_mapping(
3238         struct mm_struct *mm,
3239         unsigned long addr, unsigned long len,
3240         unsigned long vm_flags, void *priv,
3241         const struct vm_operations_struct *ops)
3242 {
3243         int ret;
3244         struct vm_area_struct *vma;
3245
3246         vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
3247         if (unlikely(vma == NULL))
3248                 return ERR_PTR(-ENOMEM);
3249
3250         INIT_LIST_HEAD(&vma->anon_vma_chain);
3251         vma->vm_mm = mm;
3252         vma->vm_start = addr;
3253         vma->vm_end = addr + len;
3254
3255         vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
3256         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
3257
3258         vma->vm_ops = ops;
3259         vma->vm_private_data = priv;
3260
3261         ret = insert_vm_struct(mm, vma);
3262         if (ret)
3263                 goto out;
3264
3265         vm_stat_account(mm, vma->vm_flags, len >> PAGE_SHIFT);
3266
3267         perf_event_mmap(vma);
3268
3269         return vma;
3270
3271 out:
3272         kmem_cache_free(vm_area_cachep, vma);
3273         return ERR_PTR(ret);
3274 }
3275
3276 bool vma_is_special_mapping(const struct vm_area_struct *vma,
3277         const struct vm_special_mapping *sm)
3278 {
3279         return vma->vm_private_data == sm &&
3280                 (vma->vm_ops == &special_mapping_vmops ||
3281                  vma->vm_ops == &legacy_special_mapping_vmops);
3282 }
3283
3284 /*
3285  * Called with mm->mmap_sem held for writing.
3286  * Insert a new vma covering the given region, with the given flags.
3287  * Its pages are supplied by the given array of struct page *.
3288  * The array can be shorter than len >> PAGE_SHIFT if it's null-terminated.
3289  * The region past the last page supplied will always produce SIGBUS.
3290  * The array pointer and the pages it points to are assumed to stay alive
3291  * for as long as this mapping might exist.
3292  */
3293 struct vm_area_struct *_install_special_mapping(
3294         struct mm_struct *mm,
3295         unsigned long addr, unsigned long len,
3296         unsigned long vm_flags, const struct vm_special_mapping *spec)
3297 {
3298         return __install_special_mapping(mm, addr, len, vm_flags, (void *)spec,
3299                                         &special_mapping_vmops);
3300 }
3301
3302 int install_special_mapping(struct mm_struct *mm,
3303                             unsigned long addr, unsigned long len,
3304                             unsigned long vm_flags, struct page **pages)
3305 {
3306         struct vm_area_struct *vma = __install_special_mapping(
3307                 mm, addr, len, vm_flags, (void *)pages,
3308                 &legacy_special_mapping_vmops);
3309
3310         return PTR_ERR_OR_ZERO(vma);
3311 }
3312
3313 static DEFINE_MUTEX(mm_all_locks_mutex);
3314
3315 static void vm_lock_anon_vma(struct mm_struct *mm, struct anon_vma *anon_vma)
3316 {
3317         if (!test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_node)) {
3318                 /*
3319                  * The LSB of head.next can't change from under us
3320                  * because we hold the mm_all_locks_mutex.
3321                  */
3322                 down_write_nest_lock(&anon_vma->root->rwsem, &mm->mmap_sem);
3323                 /*
3324                  * We can safely modify head.next after taking the
3325                  * anon_vma->root->rwsem. If some other vma in this mm shares
3326                  * the same anon_vma we won't take it again.
3327                  *
3328                  * No need of atomic instructions here, head.next
3329                  * can't change from under us thanks to the
3330                  * anon_vma->root->rwsem.
3331                  */
3332                 if (__test_and_set_bit(0, (unsigned long *)
3333                                        &anon_vma->root->rb_root.rb_node))
3334                         BUG();
3335         }
3336 }
3337
3338 static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping)
3339 {
3340         if (!test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3341                 /*
3342                  * AS_MM_ALL_LOCKS can't change from under us because
3343                  * we hold the mm_all_locks_mutex.
3344                  *
3345                  * Operations on ->flags have to be atomic because
3346                  * even if AS_MM_ALL_LOCKS is stable thanks to the
3347                  * mm_all_locks_mutex, there may be other cpus
3348                  * changing other bitflags in parallel to us.
3349                  */
3350                 if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags))
3351                         BUG();
3352                 down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_sem);
3353         }
3354 }
3355
3356 /*
3357  * This operation locks against the VM for all pte/vma/mm related
3358  * operations that could ever happen on a certain mm. This includes
3359  * vmtruncate, try_to_unmap, and all page faults.
3360  *
3361  * The caller must take the mmap_sem in write mode before calling
3362  * mm_take_all_locks(). The caller isn't allowed to release the
3363  * mmap_sem until mm_drop_all_locks() returns.
3364  *
3365  * mmap_sem in write mode is required in order to block all operations
3366  * that could modify pagetables and free pages without need of
3367  * altering the vma layout. It's also needed in write mode to avoid new
3368  * anon_vmas to be associated with existing vmas.
3369  *
3370  * A single task can't take more than one mm_take_all_locks() in a row
3371  * or it would deadlock.
3372  *
3373  * The LSB in anon_vma->rb_root.rb_node and the AS_MM_ALL_LOCKS bitflag in
3374  * mapping->flags avoid to take the same lock twice, if more than one
3375  * vma in this mm is backed by the same anon_vma or address_space.
3376  *
3377  * We take locks in following order, accordingly to comment at beginning
3378  * of mm/rmap.c:
3379  *   - all hugetlbfs_i_mmap_rwsem_key locks (aka mapping->i_mmap_rwsem for
3380  *     hugetlb mapping);
3381  *   - all i_mmap_rwsem locks;
3382  *   - all anon_vma->rwseml
3383  *
3384  * We can take all locks within these types randomly because the VM code
3385  * doesn't nest them and we protected from parallel mm_take_all_locks() by
3386  * mm_all_locks_mutex.
3387  *
3388  * mm_take_all_locks() and mm_drop_all_locks are expensive operations
3389  * that may have to take thousand of locks.
3390  *
3391  * mm_take_all_locks() can fail if it's interrupted by signals.
3392  */
3393 int mm_take_all_locks(struct mm_struct *mm)
3394 {
3395         struct vm_area_struct *vma;
3396         struct anon_vma_chain *avc;
3397
3398         BUG_ON(down_read_trylock(&mm->mmap_sem));
3399
3400         mutex_lock(&mm_all_locks_mutex);
3401
3402         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3403                 if (signal_pending(current))
3404                         goto out_unlock;
3405                 if (vma->vm_file && vma->vm_file->f_mapping &&
3406                                 is_vm_hugetlb_page(vma))
3407                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3408         }
3409
3410         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3411                 if (signal_pending(current))
3412                         goto out_unlock;
3413                 if (vma->vm_file && vma->vm_file->f_mapping &&
3414                                 !is_vm_hugetlb_page(vma))
3415                         vm_lock_mapping(mm, vma->vm_file->f_mapping);
3416         }
3417
3418         for (vma = mm->mmap; vma; vma = vma->vm_next) {
3419                 if (signal_pending(current))
3420                         goto out_unlock;
3421                 if (vma->anon_vma)
3422                         list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
3423                                 vm_lock_anon_vma(mm, avc->anon_vma);
3424         }
3425
3426         return 0;
3427
3428 out_unlock:
3429         mm_drop_all_locks(mm);
3430         return -EINTR;
3431 }
3432
3433 static void vm_unlock_anon_vma(struct anon_vma *anon_vma)
3434 {
3435         if (test_bit(0, (unsigned long *) &anon_vma->root->rb_root.rb_node)) {
3436                 /*
3437                  * The LSB of head.next can't change to 0 from under
3438                  * us because we hold the mm_all_locks_mutex.
3439                  *
3440                  * We must however clear the bitflag before unlocking
3441                  * the vma so the users using the anon_vma->rb_root will
3442                  * never see our bitflag.
3443                  *
3444                  * No need of atomic instructions here, head.next
3445                  * can't change from under us until we release the
3446                  * anon_vma->root->rwsem.
3447                  */
3448                 if (!__test_and_clear_bit(0, (unsigned long *)
3449                                           &anon_vma->root->rb_root.rb_node))
3450                         BUG();
3451                 anon_vma_unlock_write(anon_vma);
3452         }
3453 }
3454
3455 static void vm_unlock_mapping(struct address_space *mapping)
3456 {
3457         if (test_bit(AS_MM_ALL_LOCKS, &mapping->flags)) {
3458                 /*
3459                  * AS_MM_ALL_LOCKS can't change to 0 from under us
3460                  * because we hold the mm_all_locks_mutex.
3461                  */
3462                 i_mmap_unlock_write(mapping);
3463                 if (!test_and_clear_bit(AS_MM_ALL_LOCKS,
3464                                         &mapping->flags))
3465                         BUG();
3466         }
3467 }
3468
3469 /*
3470  * The mmap_sem cannot be released by the caller until