fs/pipe.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/fs/pipe.c
   4  *
   5  *  Copyright (C) 1991, 1992, 1999  Linus Torvalds
   6  */
   7
   8 #include <linux/mm.h>
   9 #include <linux/file.h>
  10 #include <linux/poll.h>
  11 #include <linux/slab.h>
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/fs.h>
  15 #include <linux/log2.h>
  16 #include <linux/mount.h>
  17 #include <linux/magic.h>
  18 #include <linux/pipe_fs_i.h>
  19 #include <linux/uio.h>
  20 #include <linux/highmem.h>
  21 #include <linux/pagemap.h>
  22 #include <linux/audit.h>
  23 #include <linux/syscalls.h>
  24 #include <linux/fcntl.h>
  25 #include <linux/memcontrol.h>
  26
  27 #include <linux/uaccess.h>
  28 #include <asm/ioctls.h>
  29
  30 #include "internal.h"
  31
  32 /*
  33  * The max size that a non-root user is allowed to grow the pipe. Can
  34  * be set by root in /proc/sys/fs/pipe-max-size
  35  */
  36 unsigned int pipe_max_size = 1048576;
  37
  38 /* Maximum allocatable pages per user. Hard limit is unset by default, soft
  39  * matches default values.
  40  */
  41 unsigned long pipe_user_pages_hard;
  42 unsigned long pipe_user_pages_soft = PIPE_DEF_BUFFERS * INR_OPEN_CUR;
  43
  44 /*
  45  * We use a start+len construction, which provides full use of the
  46  * allocated memory.
  47  * -- Florian Coosmann (FGC)
  48  *
  49  * Reads with count = 0 should always return 0.
  50  * -- Julian Bradfield 1999-06-07.
  51  *
  52  * FIFOs and Pipes now generate SIGIO for both readers and writers.
  53  * -- Jeremy Elson <jelson@circlemud.org> 2001-08-16
  54  *
  55  * pipe_read & write cleanup
  56  * -- Manfred Spraul <manfred@colorfullife.com> 2002-05-09
  57  */
  58
  59 static void pipe_lock_nested(struct pipe_inode_info *pipe, int subclass)
  60 {
  61         if (pipe->files)
  62                 mutex_lock_nested(&pipe->mutex, subclass);
  63 }
  64
  65 void pipe_lock(struct pipe_inode_info *pipe)
  66 {
  67         /*
  68          * pipe_lock() nests non-pipe inode locks (for writing to a file)
  69          */
  70         pipe_lock_nested(pipe, I_MUTEX_PARENT);
  71 }
  72 EXPORT_SYMBOL(pipe_lock);
  73
  74 void pipe_unlock(struct pipe_inode_info *pipe)
  75 {
  76         if (pipe->files)
  77                 mutex_unlock(&pipe->mutex);
  78 }
  79 EXPORT_SYMBOL(pipe_unlock);
  80
  81 static inline void __pipe_lock(struct pipe_inode_info *pipe)
  82 {
  83         mutex_lock_nested(&pipe->mutex, I_MUTEX_PARENT);
  84 }
  85
  86 static inline void __pipe_unlock(struct pipe_inode_info *pipe)
  87 {
  88         mutex_unlock(&pipe->mutex);
  89 }
  90
  91 void pipe_double_lock(struct pipe_inode_info *pipe1,
  92                       struct pipe_inode_info *pipe2)
  93 {
  94         BUG_ON(pipe1 == pipe2);
  95
  96         if (pipe1 < pipe2) {
  97                 pipe_lock_nested(pipe1, I_MUTEX_PARENT);
  98                 pipe_lock_nested(pipe2, I_MUTEX_CHILD);
  99         } else {
 100                 pipe_lock_nested(pipe2, I_MUTEX_PARENT);
 101                 pipe_lock_nested(pipe1, I_MUTEX_CHILD);
 102         }
 103 }
 104
 105 /* Drop the inode semaphore and wait for a pipe event, atomically */
 106 void pipe_wait(struct pipe_inode_info *pipe)
 107 {
 108         DEFINE_WAIT(wait);
 109
 110         /*
 111          * Pipes are system-local resources, so sleeping on them
 112          * is considered a noninteractive wait:
 113          */
 114         prepare_to_wait(&pipe->wait, &wait, TASK_INTERRUPTIBLE);
 115         pipe_unlock(pipe);
 116         schedule();
 117         finish_wait(&pipe->wait, &wait);
 118         pipe_lock(pipe);
 119 }
 120
 121 static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
 122                                   struct pipe_buffer *buf)
 123 {
 124         struct page *page = buf->page;
 125
 126         /*
 127          * If nobody else uses this page, and we don't already have a
 128          * temporary page, let's keep track of it as a one-deep
 129          * allocation cache. (Otherwise just release our reference to it)
 130          */
 131         if (page_count(page) == 1 && !pipe->tmp_page)
 132                 pipe->tmp_page = page;
 133         else
 134                 put_page(page);
 135 }
 136
 137 static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
 138                                struct pipe_buffer *buf)
 139 {
 140         struct page *page = buf->page;
 141
 142         if (page_count(page) == 1) {
 143                 if (memcg_kmem_enabled())
 144                         memcg_kmem_uncharge(page, 0);
 145                 __SetPageLocked(page);
 146                 return 0;
 147         }
 148         return 1;
 149 }
 150
 151 /**
 152  * generic_pipe_buf_steal - attempt to take ownership of a &pipe_buffer
 153  * @pipe:       the pipe that the buffer belongs to
 154  * @buf:        the buffer to attempt to steal
 155  *
 156  * Description:
 157  *      This function attempts to steal the &struct page attached to
 158  *      @buf. If successful, this function returns 0 and returns with
 159  *      the page locked. The caller may then reuse the page for whatever
 160  *      he wishes; the typical use is insertion into a different file
 161  *      page cache.
 162  */
 163 int generic_pipe_buf_steal(struct pipe_inode_info *pipe,
 164                            struct pipe_buffer *buf)
 165 {
 166         struct page *page = buf->page;
 167
 168         /*
 169          * A reference of one is golden, that means that the owner of this
 170          * page is the only one holding a reference to it. lock the page
 171          * and return OK.
 172          */
 173         if (page_count(page) == 1) {
 174                 lock_page(page);
 175                 return 0;
 176         }
 177
 178         return 1;
 179 }
 180 EXPORT_SYMBOL(generic_pipe_buf_steal);
 181
 182 /**
 183  * generic_pipe_buf_get - get a reference to a &struct pipe_buffer
 184  * @pipe:       the pipe that the buffer belongs to
 185  * @buf:        the buffer to get a reference to
 186  *
 187  * Description:
 188  *      This function grabs an extra reference to @buf. It's used in
 189  *      in the tee() system call, when we duplicate the buffers in one
 190  *      pipe into another.
 191  */
 192 void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 193 {
 194         get_page(buf->page);
 195 }
 196 EXPORT_SYMBOL(generic_pipe_buf_get);
 197
 198 /**
 199  * generic_pipe_buf_confirm - verify contents of the pipe buffer
 200  * @info:       the pipe that the buffer belongs to
 201  * @buf:        the buffer to confirm
 202  *
 203  * Description:
 204  *      This function does nothing, because the generic pipe code uses
 205  *      pages that are always good when inserted into the pipe.
 206  */
 207 int generic_pipe_buf_confirm(struct pipe_inode_info *info,
 208                              struct pipe_buffer *buf)
 209 {
 210         return 0;
 211 }
 212 EXPORT_SYMBOL(generic_pipe_buf_confirm);
 213
 214 /**
 215  * generic_pipe_buf_release - put a reference to a &struct pipe_buffer
 216  * @pipe:       the pipe that the buffer belongs to
 217  * @buf:        the buffer to put a reference to
 218  *
 219  * Description:
 220  *      This function releases a reference to @buf.
 221  */
 222 void generic_pipe_buf_release(struct pipe_inode_info *pipe,
 223                               struct pipe_buffer *buf)
 224 {
 225         put_page(buf->page);
 226 }
 227 EXPORT_SYMBOL(generic_pipe_buf_release);
 228
 229 static const struct pipe_buf_operations anon_pipe_buf_ops = {
 230         .can_merge = 1,
 231         .confirm = generic_pipe_buf_confirm,
 232         .release = anon_pipe_buf_release,
 233         .steal = anon_pipe_buf_steal,
 234         .get = generic_pipe_buf_get,
 235 };
 236
 237 static const struct pipe_buf_operations packet_pipe_buf_ops = {
 238         .can_merge = 0,
 239         .confirm = generic_pipe_buf_confirm,
 240         .release = anon_pipe_buf_release,
 241         .steal = anon_pipe_buf_steal,
 242         .get = generic_pipe_buf_get,
 243 };
 244
 245 static ssize_t
 246 pipe_read(struct kiocb *iocb, struct iov_iter *to)
 247 {
 248         size_t total_len = iov_iter_count(to);
 249         struct file *filp = iocb->ki_filp;
 250         struct pipe_inode_info *pipe = filp->private_data;
 251         int do_wakeup;
 252         ssize_t ret;
 253
 254         /* Null read succeeds. */
 255         if (unlikely(total_len == 0))
 256                 return 0;
 257
 258         do_wakeup = 0;
 259         ret = 0;
 260         __pipe_lock(pipe);
 261         for (;;) {
 262                 int bufs = pipe->nrbufs;
 263                 if (bufs) {
 264                         int curbuf = pipe->curbuf;
 265                         struct pipe_buffer *buf = pipe->bufs + curbuf;
 266                         size_t chars = buf->len;
 267                         size_t written;
 268                         int error;
 269
 270                         if (chars > total_len)
 271                                 chars = total_len;
 272
 273                         error = pipe_buf_confirm(pipe, buf);
 274                         if (error) {
 275                                 if (!ret)
 276                                         ret = error;
 277                                 break;
 278                         }
 279
 280                         written = copy_page_to_iter(buf->page, buf->offset, chars, to);
 281                         if (unlikely(written < chars)) {
 282                                 if (!ret)
 283                                         ret = -EFAULT;
 284                                 break;
 285                         }
 286                         ret += chars;
 287                         buf->offset += chars;
 288                         buf->len -= chars;
 289
 290                         /* Was it a packet buffer? Clean up and exit */
 291                         if (buf->flags & PIPE_BUF_FLAG_PACKET) {
 292                                 total_len = chars;
 293                                 buf->len = 0;
 294                         }
 295
 296                         if (!buf->len) {
 297                                 pipe_buf_release(pipe, buf);
 298                                 curbuf = (curbuf + 1) & (pipe->buffers - 1);
 299                                 pipe->curbuf = curbuf;
 300                                 pipe->nrbufs = --bufs;
 301                                 do_wakeup = 1;
 302                         }
 303                         total_len -= chars;
 304                         if (!total_len)
 305                                 break;  /* common path: read succeeded */
 306                 }
 307                 if (bufs)       /* More to do? */
 308                         continue;
 309                 if (!pipe->writers)
 310                         break;
 311                 if (!pipe->waiting_writers) {
 312                         /* syscall merging: Usually we must not sleep
 313                          * if O_NONBLOCK is set, or if we got some data.
 314                          * But if a writer sleeps in kernel space, then
 315                          * we can wait for that data without violating POSIX.
 316                          */
 317                         if (ret)
 318                                 break;
 319                         if (filp->f_flags & O_NONBLOCK) {
 320                                 ret = -EAGAIN;
 321                                 break;
 322                         }
 323                 }
 324                 if (signal_pending(current)) {
 325                         if (!ret)
 326                                 ret = -ERESTARTSYS;
 327                         break;
 328                 }
 329                 if (do_wakeup) {
 330                         wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
 331                         kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 332                 }
 333                 pipe_wait(pipe);
 334         }
 335         __pipe_unlock(pipe);
 336
 337         /* Signal writers asynchronously that there is more room. */
 338         if (do_wakeup) {
 339                 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
 340                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 341         }
 342         if (ret > 0)
 343                 file_accessed(filp);
 344         return ret;
 345 }
 346
 347 static inline int is_packetized(struct file *file)
 348 {
 349         return (file->f_flags & O_DIRECT) != 0;
 350 }
 351
 352 static ssize_t
 353 pipe_write(struct kiocb *iocb, struct iov_iter *from)
 354 {
 355         struct file *filp = iocb->ki_filp;
 356         struct pipe_inode_info *pipe = filp->private_data;
 357         ssize_t ret = 0;
 358         int do_wakeup = 0;
 359         size_t total_len = iov_iter_count(from);
 360         ssize_t chars;
 361
 362         /* Null write succeeds. */
 363         if (unlikely(total_len == 0))
 364                 return 0;
 365
 366         __pipe_lock(pipe);
 367
 368         if (!pipe->readers) {
 369                 send_sig(SIGPIPE, current, 0);
 370                 ret = -EPIPE;
 371                 goto out;
 372         }
 373
 374         /* We try to merge small writes */
 375         chars = total_len & (PAGE_SIZE-1); /* size of the last buffer */
 376         if (pipe->nrbufs && chars != 0) {
 377                 int lastbuf = (pipe->curbuf + pipe->nrbufs - 1) &
 378                                                         (pipe->buffers - 1);
 379                 struct pipe_buffer *buf = pipe->bufs + lastbuf;
 380                 int offset = buf->offset + buf->len;
 381
 382                 if (buf->ops->can_merge && offset + chars <= PAGE_SIZE) {
 383                         ret = pipe_buf_confirm(pipe, buf);
 384                         if (ret)
 385                                 goto out;
 386
 387                         ret = copy_page_from_iter(buf->page, offset, chars, from);
 388                         if (unlikely(ret < chars)) {
 389                                 ret = -EFAULT;
 390                                 goto out;
 391                         }
 392                         do_wakeup = 1;
 393                         buf->len += ret;
 394                         if (!iov_iter_count(from))
 395                                 goto out;
 396                 }
 397         }
 398
 399         for (;;) {
 400                 int bufs;
 401
 402                 if (!pipe->readers) {
 403                         send_sig(SIGPIPE, current, 0);
 404                         if (!ret)
 405                                 ret = -EPIPE;
 406                         break;
 407                 }
 408                 bufs = pipe->nrbufs;
 409                 if (bufs < pipe->buffers) {
 410                         int newbuf = (pipe->curbuf + bufs) & (pipe->buffers-1);
 411                         struct pipe_buffer *buf = pipe->bufs + newbuf;
 412                         struct page *page = pipe->tmp_page;
 413                         int copied;
 414
 415                         if (!page) {
 416                                 page = alloc_page(GFP_HIGHUSER | __GFP_ACCOUNT);
 417                                 if (unlikely(!page)) {
 418                                         ret = ret ? : -ENOMEM;
 419                                         break;
 420                                 }
 421                                 pipe->tmp_page = page;
 422                         }
 423                         /* Always wake up, even if the copy fails. Otherwise
 424                          * we lock up (O_NONBLOCK-)readers that sleep due to
 425                          * syscall merging.
 426                          * FIXME! Is this really true?
 427                          */
 428                         do_wakeup = 1;
 429                         copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);
 430                         if (unlikely(copied < PAGE_SIZE && iov_iter_count(from))) {
 431                                 if (!ret)
 432                                         ret = -EFAULT;
 433                                 break;
 434                         }
 435                         ret += copied;
 436
 437                         /* Insert it into the buffer array */
 438                         buf->page = page;
 439                         buf->ops = &anon_pipe_buf_ops;
 440                         buf->offset = 0;
 441                         buf->len = copied;
 442                         buf->flags = 0;
 443                         if (is_packetized(filp)) {
 444                                 buf->ops = &packet_pipe_buf_ops;
 445                                 buf->flags = PIPE_BUF_FLAG_PACKET;
 446                         }
 447                         pipe->nrbufs = ++bufs;
 448                         pipe->tmp_page = NULL;
 449
 450                         if (!iov_iter_count(from))
 451                                 break;
 452                 }
 453                 if (bufs < pipe->buffers)
 454                         continue;
 455                 if (filp->f_flags & O_NONBLOCK) {
 456                         if (!ret)
 457                                 ret = -EAGAIN;
 458                         break;
 459                 }
 460                 if (signal_pending(current)) {
 461                         if (!ret)
 462                                 ret = -ERESTARTSYS;
 463                         break;
 464                 }
 465                 if (do_wakeup) {
 466                         wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
 467                         kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 468                         do_wakeup = 0;
 469                 }
 470                 pipe->waiting_writers++;
 471                 pipe_wait(pipe);
 472                 pipe->waiting_writers--;
 473         }
 474 out:
 475         __pipe_unlock(pipe);
 476         if (do_wakeup) {
 477                 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLRDNORM);
 478                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 479         }
 480         if (ret > 0 && sb_start_write_trylock(file_inode(filp)->i_sb)) {
 481                 int err = file_update_time(filp);
 482                 if (err)
 483                         ret = err;
 484                 sb_end_write(file_inode(filp)->i_sb);
 485         }
 486         return ret;
 487 }
 488
 489 static long pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 490 {
 491         struct pipe_inode_info *pipe = filp->private_data;
 492         int count, buf, nrbufs;
 493
 494         switch (cmd) {
 495                 case FIONREAD:
 496                         __pipe_lock(pipe);
 497                         count = 0;
 498                         buf = pipe->curbuf;
 499                         nrbufs = pipe->nrbufs;
 500                         while (--nrbufs >= 0) {
 501                                 count += pipe->bufs[buf].len;
 502                                 buf = (buf+1) & (pipe->buffers - 1);
 503                         }
 504                         __pipe_unlock(pipe);
 505
 506                         return put_user(count, (int __user *)arg);
 507                 default:
 508                         return -ENOIOCTLCMD;
 509         }
 510 }
 511
 512 static struct wait_queue_head *
 513 pipe_get_poll_head(struct file *filp, __poll_t events)
 514 {
 515         struct pipe_inode_info *pipe = filp->private_data;
 516
 517         return &pipe->wait;
 518 }
 519
 520 /* No kernel lock held - fine */
 521 static __poll_t pipe_poll_mask(struct file *filp, __poll_t events)
 522 {
 523         struct pipe_inode_info *pipe = filp->private_data;
 524         int nrbufs = pipe->nrbufs;
 525         __poll_t mask = 0;
 526
 527         /* Reading only -- no need for acquiring the semaphore.  */
 528         if (filp->f_mode & FMODE_READ) {
 529                 mask = (nrbufs > 0) ? EPOLLIN | EPOLLRDNORM : 0;
 530                 if (!pipe->writers && filp->f_version != pipe->w_counter)
 531                         mask |= EPOLLHUP;
 532         }
 533
 534         if (filp->f_mode & FMODE_WRITE) {
 535                 mask |= (nrbufs < pipe->buffers) ? EPOLLOUT | EPOLLWRNORM : 0;
 536                 /*
 537                  * Most Unices do not set EPOLLERR for FIFOs but on Linux they
 538                  * behave exactly like pipes for poll().
 539                  */
 540                 if (!pipe->readers)
 541                         mask |= EPOLLERR;
 542         }
 543
 544         return mask;
 545 }
 546
 547 static void put_pipe_info(struct inode *inode, struct pipe_inode_info *pipe)
 548 {
 549         int kill = 0;
 550
 551         spin_lock(&inode->i_lock);
 552         if (!--pipe->files) {
 553                 inode->i_pipe = NULL;
 554                 kill = 1;
 555         }
 556         spin_unlock(&inode->i_lock);
 557
 558         if (kill)
 559                 free_pipe_info(pipe);
 560 }
 561
 562 static int
 563 pipe_release(struct inode *inode, struct file *file)
 564 {
 565         struct pipe_inode_info *pipe = file->private_data;
 566
 567         __pipe_lock(pipe);
 568         if (file->f_mode & FMODE_READ)
 569                 pipe->readers--;
 570         if (file->f_mode & FMODE_WRITE)
 571                 pipe->writers--;
 572
 573         if (pipe->readers || pipe->writers) {
 574                 wake_up_interruptible_sync_poll(&pipe->wait, EPOLLIN | EPOLLOUT | EPOLLRDNORM | EPOLLWRNORM | EPOLLERR | EPOLLHUP);
 575                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 576                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 577         }
 578         __pipe_unlock(pipe);
 579
 580         put_pipe_info(inode, pipe);
 581         return 0;
 582 }
 583
 584 static int
 585 pipe_fasync(int fd, struct file *filp, int on)
 586 {
 587         struct pipe_inode_info *pipe = filp->private_data;
 588         int retval = 0;
 589
 590         __pipe_lock(pipe);
 591         if (filp->f_mode & FMODE_READ)
 592                 retval = fasync_helper(fd, filp, on, &pipe->fasync_readers);
 593         if ((filp->f_mode & FMODE_WRITE) && retval >= 0) {
 594                 retval = fasync_helper(fd, filp, on, &pipe->fasync_writers);
 595                 if (retval < 0 && (filp->f_mode & FMODE_READ))
 596                         /* this can happen only if on == T */
 597                         fasync_helper(-1, filp, 0, &pipe->fasync_readers);
 598         }
 599         __pipe_unlock(pipe);
 600         return retval;
 601 }
 602
 603 static unsigned long account_pipe_buffers(struct user_struct *user,
 604                                  unsigned long old, unsigned long new)
 605 {
 606         return atomic_long_add_return(new - old, &user->pipe_bufs);
 607 }
 608
 609 static bool too_many_pipe_buffers_soft(unsigned long user_bufs)
 610 {
 611         unsigned long soft_limit = READ_ONCE(pipe_user_pages_soft);
 612
 613         return soft_limit && user_bufs > soft_limit;
 614 }
 615
 616 static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
 617 {
 618         unsigned long hard_limit = READ_ONCE(pipe_user_pages_hard);
 619
 620         return hard_limit && user_bufs > hard_limit;
 621 }
 622
 623 static bool is_unprivileged_user(void)
 624 {
 625         return !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN);
 626 }
 627
 628 struct pipe_inode_info *alloc_pipe_info(void)
 629 {
 630         struct pipe_inode_info *pipe;
 631         unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
 632         struct user_struct *user = get_current_user();
 633         unsigned long user_bufs;
 634         unsigned int max_size = READ_ONCE(pipe_max_size);
 635
 636         pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
 637         if (pipe == NULL)
 638                 goto out_free_uid;
 639
 640         if (pipe_bufs * PAGE_SIZE > max_size && !capable(CAP_SYS_RESOURCE))
 641                 pipe_bufs = max_size >> PAGE_SHIFT;
 642
 643         user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
 644
 645         if (too_many_pipe_buffers_soft(user_bufs) && is_unprivileged_user()) {
 646                 user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
 647                 pipe_bufs = 1;
 648         }
 649
 650         if (too_many_pipe_buffers_hard(user_bufs) && is_unprivileged_user())
 651                 goto out_revert_acct;
 652
 653         pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
 654                              GFP_KERNEL_ACCOUNT);
 655
 656         if (pipe->bufs) {
 657                 init_waitqueue_head(&pipe->wait);
 658                 pipe->r_counter = pipe->w_counter = 1;
 659                 pipe->buffers = pipe_bufs;
 660                 pipe->user = user;
 661                 mutex_init(&pipe->mutex);
 662                 return pipe;
 663         }
 664
 665 out_revert_acct:
 666         (void) account_pipe_buffers(user, pipe_bufs, 0);
 667         kfree(pipe);
 668 out_free_uid:
 669         free_uid(user);
 670         return NULL;
 671 }
 672
 673 void free_pipe_info(struct pipe_inode_info *pipe)
 674 {
 675         int i;
 676
 677         (void) account_pipe_buffers(pipe->user, pipe->buffers, 0);
 678         free_uid(pipe->user);
 679         for (i = 0; i < pipe->buffers; i++) {
 680                 struct pipe_buffer *buf = pipe->bufs + i;
 681                 if (buf->ops)
 682                         pipe_buf_release(pipe, buf);
 683         }
 684         if (pipe->tmp_page)
 685                 __free_page(pipe->tmp_page);
 686         kfree(pipe->bufs);
 687         kfree(pipe);
 688 }
 689
 690 static struct vfsmount *pipe_mnt __read_mostly;
 691
 692 /*
 693  * pipefs_dname() is called from d_path().
 694  */
 695 static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
 696 {
 697         return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
 698                                 d_inode(dentry)->i_ino);
 699 }
 700
 701 static const struct dentry_operations pipefs_dentry_operations = {
 702         .d_dname        = pipefs_dname,
 703 };
 704
 705 static struct inode * get_pipe_inode(void)
 706 {
 707         struct inode *inode = new_inode_pseudo(pipe_mnt->mnt_sb);
 708         struct pipe_inode_info *pipe;
 709
 710         if (!inode)
 711                 goto fail_inode;
 712
 713         inode->i_ino = get_next_ino();
 714
 715         pipe = alloc_pipe_info();
 716         if (!pipe)
 717                 goto fail_iput;
 718
 719         inode->i_pipe = pipe;
 720         pipe->files = 2;
 721         pipe->readers = pipe->writers = 1;
 722         inode->i_fop = &pipefifo_fops;
 723
 724         /*
 725          * Mark the inode dirty from the very beginning,
 726          * that way it will never be moved to the dirty
 727          * list because "mark_inode_dirty()" will think
 728          * that it already _is_ on the dirty list.
 729          */
 730         inode->i_state = I_DIRTY;
 731         inode->i_mode = S_IFIFO | S_IRUSR | S_IWUSR;
 732         inode->i_uid = current_fsuid();
 733         inode->i_gid = current_fsgid();
 734         inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 735
 736         return inode;
 737
 738 fail_iput:
 739         iput(inode);
 740
 741 fail_inode:
 742         return NULL;
 743 }
 744
 745 int create_pipe_files(struct file **res, int flags)
 746 {
 747         struct inode *inode = get_pipe_inode();
 748         struct file *f;
 749
 750         if (!inode)
 751                 return -ENFILE;
 752
 753         f = alloc_file_pseudo(inode, pipe_mnt, "",
 754                                 O_WRONLY | (flags & (O_NONBLOCK | O_DIRECT)),
 755                                 &pipefifo_fops);
 756         if (IS_ERR(f)) {
 757                 free_pipe_info(inode->i_pipe);
 758                 iput(inode);
 759                 return PTR_ERR(f);
 760         }
 761
 762         f->private_data = inode->i_pipe;
 763
 764         res[0] = alloc_file(&f->f_path, O_RDONLY | (flags & O_NONBLOCK),
 765                         &pipefifo_fops);
 766         if (IS_ERR(res[0])) {
 767                 put_pipe_info(inode, inode->i_pipe);
 768                 fput(f);
 769                 return PTR_ERR(res[0]);
 770         }
 771
 772         path_get(&f->f_path);
 773         res[0]->private_data = inode->i_pipe;
 774         res[1] = f;
 775         return 0;
 776 }
 777
 778 static int __do_pipe_flags(int *fd, struct file **files, int flags)
 779 {
 780         int error;
 781         int fdw, fdr;
 782
 783         if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT))
 784                 return -EINVAL;
 785
 786         error = create_pipe_files(files, flags);
 787         if (error)
 788                 return error;
 789
 790         error = get_unused_fd_flags(flags);
 791         if (error < 0)
 792                 goto err_read_pipe;
 793         fdr = error;
 794
 795         error = get_unused_fd_flags(flags);
 796         if (error < 0)
 797                 goto err_fdr;
 798         fdw = error;
 799
 800         audit_fd_pair(fdr, fdw);
 801         fd[0] = fdr;
 802         fd[1] = fdw;
 803         return 0;
 804
 805  err_fdr:
 806         put_unused_fd(fdr);
 807  err_read_pipe:
 808         fput(files[0]);
 809         fput(files[1]);
 810         return error;
 811 }
 812
 813 int do_pipe_flags(int *fd, int flags)
 814 {
 815         struct file *files[2];
 816         int error = __do_pipe_flags(fd, files, flags);
 817         if (!error) {
 818                 fd_install(fd[0], files[0]);
 819                 fd_install(fd[1], files[1]);
 820         }
 821         return error;
 822 }
 823
 824 /*
 825  * sys_pipe() is the normal C calling standard for creating
 826  * a pipe. It's not the way Unix traditionally does this, though.
 827  */
 828 static int do_pipe2(int __user *fildes, int flags)
 829 {
 830         struct file *files[2];
 831         int fd[2];
 832         int error;
 833
 834         error = __do_pipe_flags(fd, files, flags);
 835         if (!error) {
 836                 if (unlikely(copy_to_user(fildes, fd, sizeof(fd)))) {
 837                         fput(files[0]);
 838                         fput(files[1]);
 839                         put_unused_fd(fd[0]);
 840                         put_unused_fd(fd[1]);
 841                         error = -EFAULT;
 842                 } else {
 843                         fd_install(fd[0], files[0]);
 844                         fd_install(fd[1], files[1]);
 845                 }
 846         }
 847         return error;
 848 }
 849
 850 SYSCALL_DEFINE2(pipe2, int __user *, fildes, int, flags)
 851 {
 852         return do_pipe2(fildes, flags);
 853 }
 854
 855 SYSCALL_DEFINE1(pipe, int __user *, fildes)
 856 {
 857         return do_pipe2(fildes, 0);
 858 }
 859
 860 static int wait_for_partner(struct pipe_inode_info *pipe, unsigned int *cnt)
 861 {
 862         int cur = *cnt;
 863
 864         while (cur == *cnt) {
 865                 pipe_wait(pipe);
 866                 if (signal_pending(current))
 867                         break;
 868         }
 869         return cur == *cnt ? -ERESTARTSYS : 0;
 870 }
 871
 872 static void wake_up_partner(struct pipe_inode_info *pipe)
 873 {
 874         wake_up_interruptible(&pipe->wait);
 875 }
 876
 877 static int fifo_open(struct inode *inode, struct file *filp)
 878 {
 879         struct pipe_inode_info *pipe;
 880         bool is_pipe = inode->i_sb->s_magic == PIPEFS_MAGIC;
 881         int ret;
 882
 883         filp->f_version = 0;
 884
 885         spin_lock(&inode->i_lock);
 886         if (inode->i_pipe) {
 887                 pipe = inode->i_pipe;
 888                 pipe->files++;
 889                 spin_unlock(&inode->i_lock);
 890         } else {
 891                 spin_unlock(&inode->i_lock);
 892                 pipe = alloc_pipe_info();
 893                 if (!pipe)
 894                         return -ENOMEM;
 895                 pipe->files = 1;
 896                 spin_lock(&inode->i_lock);
 897                 if (unlikely(inode->i_pipe)) {
 898                         inode->i_pipe->files++;
 899                         spin_unlock(&inode->i_lock);
 900                         free_pipe_info(pipe);
 901                         pipe = inode->i_pipe;
 902                 } else {
 903                         inode->i_pipe = pipe;
 904                         spin_unlock(&inode->i_lock);
 905                 }
 906         }
 907         filp->private_data = pipe;
 908         /* OK, we have a pipe and it's pinned down */
 909
 910         __pipe_lock(pipe);
 911
 912         /* We can only do regular read/write on fifos */
 913         filp->f_mode &= (FMODE_READ | FMODE_WRITE);
 914
 915         switch (filp->f_mode) {
 916         case FMODE_READ:
 917         /*
 918          *  O_RDONLY
 919          *  POSIX.1 says that O_NONBLOCK means return with the FIFO
 920          *  opened, even when there is no process writing the FIFO.
 921          */
 922                 pipe->r_counter++;
 923                 if (pipe->readers++ == 0)
 924                         wake_up_partner(pipe);
 925
 926                 if (!is_pipe && !pipe->writers) {
 927                         if ((filp->f_flags & O_NONBLOCK)) {
 928                                 /* suppress EPOLLHUP until we have
 929                                  * seen a writer */
 930                                 filp->f_version = pipe->w_counter;
 931                         } else {
 932                                 if (wait_for_partner(pipe, &pipe->w_counter))
 933                                         goto err_rd;
 934                         }
 935                 }
 936                 break;
 937
 938         case FMODE_WRITE:
 939         /*
 940          *  O_WRONLY
 941          *  POSIX.1 says that O_NONBLOCK means return -1 with
 942          *  errno=ENXIO when there is no process reading the FIFO.
 943          */
 944                 ret = -ENXIO;
 945                 if (!is_pipe && (filp->f_flags & O_NONBLOCK) && !pipe->readers)
 946                         goto err;
 947
 948                 pipe->w_counter++;
 949                 if (!pipe->writers++)
 950                         wake_up_partner(pipe);
 951
 952                 if (!is_pipe && !pipe->readers) {
 953                         if (wait_for_partner(pipe, &pipe->r_counter))
 954                                 goto err_wr;
 955                 }
 956                 break;
 957
 958         case FMODE_READ | FMODE_WRITE:
 959         /*
 960          *  O_RDWR
 961          *  POSIX.1 leaves this case "undefined" when O_NONBLOCK is set.
 962          *  This implementation will NEVER block on a O_RDWR open, since
 963          *  the process can at least talk to itself.
 964          */
 965
 966                 pipe->readers++;
 967                 pipe->writers++;
 968                 pipe->r_counter++;
 969                 pipe->w_counter++;
 970                 if (pipe->readers == 1 || pipe->writers == 1)
 971                         wake_up_partner(pipe);
 972                 break;
 973
 974         default:
 975                 ret = -EINVAL;
 976                 goto err;
 977         }
 978
 979         /* Ok! */
 980         __pipe_unlock(pipe);
 981         return 0;
 982
 983 err_rd:
 984         if (!--pipe->readers)
 985                 wake_up_interruptible(&pipe->wait);
 986         ret = -ERESTARTSYS;
 987         goto err;
 988
 989 err_wr:
 990         if (!--pipe->writers)
 991                 wake_up_interruptible(&pipe->wait);
 992         ret = -ERESTARTSYS;
 993         goto err;
 994
 995 err:
 996         __pipe_unlock(pipe);
 997
 998         put_pipe_info(inode, pipe);
 999         return ret;
1000 }
1001
1002 const struct file_operations pipefifo_fops = {
1003         .open           = fifo_open,
1004         .llseek         = no_llseek,
1005         .read_iter      = pipe_read,
1006         .write_iter     = pipe_write,
1007         .get_poll_head  = pipe_get_poll_head,
1008         .poll_mask      = pipe_poll_mask,
1009         .unlocked_ioctl = pipe_ioctl,
1010         .release        = pipe_release,
1011         .fasync         = pipe_fasync,
1012 };
1013
1014 /*
1015  * Currently we rely on the pipe array holding a power-of-2 number
1016  * of pages. Returns 0 on error.
1017  */
1018 unsigned int round_pipe_size(unsigned long size)
1019 {
1020         if (size > (1U << 31))
1021                 return 0;
1022
1023         /* Minimum pipe size, as required by POSIX */
1024         if (size < PAGE_SIZE)
1025                 return PAGE_SIZE;
1026
1027         return roundup_pow_of_two(size);
1028 }
1029
1030 /*
1031  * Allocate a new array of pipe buffers and copy the info over. Returns the
1032  * pipe size if successful, or return -ERROR on error.
1033  */
1034 static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
1035 {
1036         struct pipe_buffer *bufs;
1037         unsigned int size, nr_pages;
1038         unsigned long user_bufs;
1039         long ret = 0;
1040
1041         size = round_pipe_size(arg);
1042         nr_pages = size >> PAGE_SHIFT;
1043
1044         if (!nr_pages)
1045                 return -EINVAL;
1046
1047         /*
1048          * If trying to increase the pipe capacity, check that an
1049          * unprivileged user is not trying to exceed various limits
1050          * (soft limit check here, hard limit check just below).
1051          * Decreasing the pipe capacity is always permitted, even
1052          * if the user is currently over a limit.
1053          */
1054         if (nr_pages > pipe->buffers &&
1055                         size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
1056                 return -EPERM;
1057
1058         user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
1059
1060         if (nr_pages > pipe->buffers &&
1061                         (too_many_pipe_buffers_hard(user_bufs) ||
1062                          too_many_pipe_buffers_soft(user_bufs)) &&
1063                         is_unprivileged_user()) {
1064                 ret = -EPERM;
1065                 goto out_revert_acct;
1066         }
1067
1068         /*
1069          * We can shrink the pipe, if arg >= pipe->nrbufs. Since we don't
1070          * expect a lot of shrink+grow operations, just free and allocate
1071          * again like we would do for growing. If the pipe currently
1072          * contains more buffers than arg, then return busy.
1073          */
1074         if (nr_pages < pipe->nrbufs) {
1075                 ret = -EBUSY;
1076                 goto out_revert_acct;
1077         }
1078
1079         bufs = kcalloc(nr_pages, sizeof(*bufs),
1080                        GFP_KERNEL_ACCOUNT | __GFP_NOWARN);
1081         if (unlikely(!bufs)) {
1082                 ret = -ENOMEM;
1083                 goto out_revert_acct;
1084         }
1085
1086         /*
1087          * The pipe array wraps around, so just start the new one at zero
1088          * and adjust the indexes.
1089          */
1090         if (pipe->nrbufs) {
1091                 unsigned int tail;
1092                 unsigned int head;
1093
1094                 tail = pipe->curbuf + pipe->nrbufs;
1095                 if (tail < pipe->buffers)
1096                         tail = 0;
1097                 else
1098                         tail &= (pipe->buffers - 1);
1099
1100                 head = pipe->nrbufs - tail;
1101                 if (head)
1102                         memcpy(bufs, pipe->bufs + pipe->curbuf, head * sizeof(struct pipe_buffer));
1103                 if (tail)
1104                         memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
1105         }
1106
1107         pipe->curbuf = 0;
1108         kfree(pipe->bufs);
1109         pipe->bufs = bufs;
1110         pipe->buffers = nr_pages;
1111         return nr_pages * PAGE_SIZE;
1112
1113 out_revert_acct:
1114         (void) account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
1115         return ret;
1116 }
1117
1118 /*
1119  * After the inode slimming patch, i_pipe/i_bdev/i_cdev share the same
1120  * location, so checking ->i_pipe is not enough to verify that this is a
1121  * pipe.
1122  */
1123 struct pipe_inode_info *get_pipe_info(struct file *file)
1124 {
1125         return file->f_op == &pipefifo_fops ? file->private_data : NULL;
1126 }
1127
1128 long pipe_fcntl(struct file *file, unsigned int cmd, unsigned long arg)
1129 {
1130         struct pipe_inode_info *pipe;
1131         long ret;
1132
1133         pipe = get_pipe_info(file);
1134         if (!pipe)
1135                 return -EBADF;
1136
1137         __pipe_lock(pipe);
1138
1139         switch (cmd) {
1140         case F_SETPIPE_SZ:
1141                 ret = pipe_set_size(pipe, arg);
1142                 break;
1143         case F_GETPIPE_SZ:
1144                 ret = pipe->buffers * PAGE_SIZE;
1145                 break;
1146         default:
1147                 ret = -EINVAL;
1148                 break;
1149         }
1150
1151         __pipe_unlock(pipe);
1152         return ret;
1153 }
1154
1155 static const struct super_operations pipefs_ops = {
1156         .destroy_inode = free_inode_nonrcu,
1157         .statfs = simple_statfs,
1158 };
1159
1160 /*
1161  * pipefs should _never_ be mounted by userland - too much of security hassle,
1162  * no real gain from having the whole whorehouse mounted. So we don't need
1163  * any operations on the root directory. However, we need a non-trivial
1164  * d_name - pipe: will go nicely and kill the special-casing in procfs.
1165  */
1166 static struct dentry *pipefs_mount(struct file_system_type *fs_type,
1167                          int flags, const char *dev_name, void *data)
1168 {
1169         return mount_pseudo(fs_type, "pipe:", &pipefs_ops,
1170                         &pipefs_dentry_operations, PIPEFS_MAGIC);
1171 }
1172
1173 static struct file_system_type pipe_fs_type = {
1174         .name           = "pipefs",
1175         .mount          = pipefs_mount,
1176         .kill_sb        = kill_anon_super,
1177 };
1178
1179 static int __init init_pipe_fs(void)
1180 {
1181         int err = register_filesystem(&pipe_fs_type);
1182
1183         if (!err) {
1184                 pipe_mnt = kern_mount(&pipe_fs_type);
1185                 if (IS_ERR(pipe_mnt)) {
1186                         err = PTR_ERR(pipe_mnt);
1187                         unregister_filesystem(&pipe_fs_type);
1188                 }
1189         }
1190         return err;
1191 }
1192
1193 fs_initcall(init_pipe_fs);