Merge branch 'uaccess-work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel...

Pull iov_iter hardening from Al Viro:
 "This is the iov_iter/uaccess/hardening pile.

  For one thing, it trims the inline part of copy_to_user/copy_from_user
  to the minimum that *does* need to be inlined - object size checks,
  basically. For another, it sanitizes the checks for iov_iter
  primitives. There are 4 groups of checks: access_ok(), might_fault(),
  object size and KASAN.

   - access_ok() had been verified by whoever had set the iov_iter up.
     However, that has happened in a function far away, so proving that
     there's no path to actual copying bypassing those checks is hard
     and proving that iov_iter has not been buggered in the meanwhile is
     also not pleasant. So we want those redone in actual
     copyin/copyout.

   - might_fault() is better off consolidated - we know whether it needs
     to be checked as soon as we enter iov_iter primitive and observe
     the iov_iter flavour. No need to wait until the copyin/copyout. The
     call chains are short enough to make sure we won't miss anything -
     in fact, it's more robust that way, since there are cases where we
     do e.g. forced fault-in before getting to copyin/copyout. It's not
     quite what we need to check (in particular, combination of
     iovec-backed and set_fs(KERNEL_DS) is almost certainly a bug, not a
     cause to skip checks), but that's for later series. For now let's
     keep might_fault().

   - KASAN checks belong in copyin/copyout - at the same level where
     other iov_iter flavours would've hit them in memcpy().

   - object size checks should apply to *all* iov_iter flavours, not
     just iovec-backed ones.

  There are two groups of primitives - one gets the kernel object
  described as pointer + size (copy_to_iter(), etc.) while another gets
  it as page + offset + size (copy_page_to_iter(), etc.)

  For the first group the checks are best done where we actually have a
  chance to find the object size. In other words, those belong in inline
  wrappers in uio.h, before calling into iov_iter.c. Same kind as we
  have for inlined part of copy_to_user().

  For the second group there is no object to look at - offset in page is
  just a number, it bears no type information. So we do them in the
  common helper called by iov_iter.c primitives of that kind. All it
  currently does is checking that we are not trying to access outside of
  the compound page; eventually we might want to add some sanity checks
  on the page involved.

  So the things we need in copyin/copyout part of iov_iter.c do not
  quite match anything in uaccess.h (we want no zeroing, we *do* want
  access_ok() and KASAN and we want no might_fault() or object size
  checks done on that level). OTOH, these needs are simple enough to
  provide a couple of helpers (static in iov_iter.c) doing just what we
  need..."

* 'uaccess-work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  iov_iter: saner checks on copyin/copyout
  iov_iter: sanity checks for copy to/from page primitives
  iov_iter/hardening: move object size checks to inlined part
  copy_{to,from}_user(): consolidate object size checks
  copy_{from,to}_user(): move kasan checks and might_fault() out-of-line

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index d7d3ea637dd0a500875cbe64c00eb5e0188acd41..250a27614328471e4a805884a952881116a14c3e 100644 (file)
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -113,6 +113,33 @@ static inline void check_object_size(const void *ptr, unsigned long n,
 { }
 #endif /* CONFIG_HARDENED_USERCOPY */
 
+extern void __compiletime_error("copy source size is too small")
+__bad_copy_from(void);
+extern void __compiletime_error("copy destination size is too small")
+__bad_copy_to(void);
+
+static inline void copy_overflow(int size, unsigned long count)
+{
+       WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
+}
+
+static __always_inline bool
+check_copy_size(const void *addr, size_t bytes, bool is_source)
+{
+       int sz = __compiletime_object_size(addr);
+       if (unlikely(sz >= 0 && sz < bytes)) {
+               if (!__builtin_constant_p(bytes))
+                       copy_overflow(sz, bytes);
+               else if (is_source)
+                       __bad_copy_from();
+               else
+                       __bad_copy_to();
+               return false;
+       }
+       check_object_size(addr, bytes, is_source);
+       return true;
+}
+
 #ifndef arch_setup_new_exec
 static inline void arch_setup_new_exec(void) { }
 #endif

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 201418d5e15c2b92dc7d7bc73b54f469eb488a35..80b587085e7913c19ab17d33a1a1ff77e51ad7ad 100644 (file)
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -109,8 +109,11 @@ static inline unsigned long
 _copy_from_user(void *to, const void __user *from, unsigned long n)
 {
        unsigned long res = n;
-       if (likely(access_ok(VERIFY_READ, from, n)))
+       might_fault();
+       if (likely(access_ok(VERIFY_READ, from, n))) {
+               kasan_check_write(to, n);
                res = raw_copy_from_user(to, from, n);
+       }
        if (unlikely(res))
                memset(to + (n - res), 0, res);
        return res;
@@ -124,8 +127,11 @@ _copy_from_user(void *, const void __user *, unsigned long);
 static inline unsigned long
 _copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-       if (access_ok(VERIFY_WRITE, to, n))
+       might_fault();
+       if (access_ok(VERIFY_WRITE, to, n)) {
+               kasan_check_read(from, n);
                n = raw_copy_to_user(to, from, n);
+       }
        return n;
 }
 #else
@@ -133,49 +139,19 @@ extern unsigned long
 _copy_to_user(void __user *, const void *, unsigned long);
 #endif
 
-extern void __compiletime_error("usercopy buffer size is too small")
-__bad_copy_user(void);
-
-static inline void copy_user_overflow(int size, unsigned long count)
-{
-       WARN(1, "Buffer overflow detected (%d < %lu)!\n", size, count);
-}
-
 static __always_inline unsigned long __must_check
 copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-       int sz = __compiletime_object_size(to);
-
-       might_fault();
-       kasan_check_write(to, n);
-
-       if (likely(sz < 0 || sz >= n)) {
-               check_object_size(to, n, false);
+       if (likely(check_copy_size(to, n, false)))
                n = _copy_from_user(to, from, n);
-       } else if (!__builtin_constant_p(n))
-               copy_user_overflow(sz, n);
-       else
-               __bad_copy_user();
-
        return n;
 }
 
 static __always_inline unsigned long __must_check
 copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-       int sz = __compiletime_object_size(from);
-
-       kasan_check_read(from, n);
-       might_fault();
-
-       if (likely(sz < 0 || sz >= n)) {
-               check_object_size(from, n, true);
+       if (likely(check_copy_size(from, n, true)))
                n = _copy_to_user(to, from, n);
-       } else if (!__builtin_constant_p(n))
-               copy_user_overflow(sz, n);
-       else
-               __bad_copy_user();
-
        return n;
 }
 #ifdef CONFIG_COMPAT

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 55cd54a0e94100cc71b4ddeb03d8b35392a32b7a..342d2dc225b95b51e36d0f9a8a37c990e69f4d74 100644 (file)
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -10,6 +10,7 @@
 #define __LINUX_UIO_H
 
 #include <linux/kernel.h>
+#include <linux/thread_info.h>
 #include <uapi/linux/uio.h>
 
 struct page;
@@ -91,10 +92,58 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
                         struct iov_iter *i);
 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
                         struct iov_iter *i);
-size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
-size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
-bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i);
-size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
+
+size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
+size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
+bool _copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i);
+size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
+bool _copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i);
+
+static __always_inline __must_check
+size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
+{
+       if (unlikely(!check_copy_size(addr, bytes, true)))
+               return bytes;
+       else
+               return _copy_to_iter(addr, bytes, i);
+}
+
+static __always_inline __must_check
+size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
+{
+       if (unlikely(!check_copy_size(addr, bytes, false)))
+               return bytes;
+       else
+               return _copy_from_iter(addr, bytes, i);
+}
+
+static __always_inline __must_check
+bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
+{
+       if (unlikely(!check_copy_size(addr, bytes, false)))
+               return false;
+       else
+               return _copy_from_iter_full(addr, bytes, i);
+}
+
+static __always_inline __must_check
+size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
+{
+       if (unlikely(!check_copy_size(addr, bytes, false)))
+               return bytes;
+       else
+               return _copy_from_iter_nocache(addr, bytes, i);
+}
+
+static __always_inline __must_check
+bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
+{
+       if (unlikely(!check_copy_size(addr, bytes, false)))
+               return false;
+       else
+               return _copy_from_iter_full_nocache(addr, bytes, i);
+}
+
 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
 /*
  * Note, users like pmem that depend on the stricter semantics of
@@ -102,15 +151,20 @@ size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i);
  * IS_ENABLED(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) before assuming that the
  * destination is flushed from the cache on return.
  */
-size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
+size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i);
 #else
-static inline size_t copy_from_iter_flushcache(void *addr, size_t bytes,
-                                      struct iov_iter *i)
+#define _copy_from_iter_flushcache _copy_from_iter_nocache
+#endif
+
+static __always_inline __must_check
+size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 {
-       return copy_from_iter_nocache(addr, bytes, i);
+       if (unlikely(!check_copy_size(addr, bytes, false)))
+               return bytes;
+       else
+               return _copy_from_iter_flushcache(addr, bytes, i);
 }
-#endif
-bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i);
+
 size_t iov_iter_zero(size_t bytes, struct iov_iter *);
 unsigned long iov_iter_alignment(const struct iov_iter *i);
 unsigned long iov_iter_gap_alignment(const struct iov_iter *i);

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index c9a69064462f8c0bf3b1a7b58623c14e7b0d371f..52c8dd6d8e8290fa8df614e0017542a600b9c536 100644 (file)
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -130,6 +130,24 @@
        }                                                       \
 }
 
+static int copyout(void __user *to, const void *from, size_t n)
+{
+       if (access_ok(VERIFY_WRITE, to, n)) {
+               kasan_check_read(from, n);
+               n = raw_copy_to_user(to, from, n);
+       }
+       return n;
+}
+
+static int copyin(void *to, const void __user *from, size_t n)
+{
+       if (access_ok(VERIFY_READ, from, n)) {
+               kasan_check_write(to, n);
+               n = raw_copy_from_user(to, from, n);
+       }
+       return n;
+}
+
 static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t bytes,
                         struct iov_iter *i)
 {
@@ -144,6 +162,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
        if (unlikely(!bytes))
                return 0;
 
+       might_fault();
        wanted = bytes;
        iov = i->iov;
        skip = i->iov_offset;
@@ -155,7 +174,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
                from = kaddr + offset;
 
                /* first chunk, usually the only one */
-               left = __copy_to_user_inatomic(buf, from, copy);
+               left = copyout(buf, from, copy);
                copy -= left;
                skip += copy;
                from += copy;
@@ -165,7 +184,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
                        iov++;
                        buf = iov->iov_base;
                        copy = min(bytes, iov->iov_len);
-                       left = __copy_to_user_inatomic(buf, from, copy);
+                       left = copyout(buf, from, copy);
                        copy -= left;
                        skip = copy;
                        from += copy;
@@ -184,7 +203,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
 
        kaddr = kmap(page);
        from = kaddr + offset;
-       left = __copy_to_user(buf, from, copy);
+       left = copyout(buf, from, copy);
        copy -= left;
        skip += copy;
        from += copy;
@@ -193,7 +212,7 @@ static size_t copy_page_to_iter_iovec(struct page *page, size_t offset, size_t b
                iov++;
                buf = iov->iov_base;
                copy = min(bytes, iov->iov_len);
-               left = __copy_to_user(buf, from, copy);
+               left = copyout(buf, from, copy);
                copy -= left;
                skip = copy;
                from += copy;
@@ -227,6 +246,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
        if (unlikely(!bytes))
                return 0;
 
+       might_fault();
        wanted = bytes;
        iov = i->iov;
        skip = i->iov_offset;
@@ -238,7 +258,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
                to = kaddr + offset;
 
                /* first chunk, usually the only one */
-               left = __copy_from_user_inatomic(to, buf, copy);
+               left = copyin(to, buf, copy);
                copy -= left;
                skip += copy;
                to += copy;
@@ -248,7 +268,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
                        iov++;
                        buf = iov->iov_base;
                        copy = min(bytes, iov->iov_len);
-                       left = __copy_from_user_inatomic(to, buf, copy);
+                       left = copyin(to, buf, copy);
                        copy -= left;
                        skip = copy;
                        to += copy;
@@ -267,7 +287,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
 
        kaddr = kmap(page);
        to = kaddr + offset;
-       left = __copy_from_user(to, buf, copy);
+       left = copyin(to, buf, copy);
        copy -= left;
        skip += copy;
        to += copy;
@@ -276,7 +296,7 @@ static size_t copy_page_from_iter_iovec(struct page *page, size_t offset, size_t
                iov++;
                buf = iov->iov_base;
                copy = min(bytes, iov->iov_len);
-               left = __copy_from_user(to, buf, copy);
+               left = copyin(to, buf, copy);
                copy -= left;
                skip = copy;
                to += copy;
@@ -535,14 +555,15 @@ static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
        return bytes;
 }
 
-size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
+size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 {
        const char *from = addr;
        if (unlikely(i->type & ITER_PIPE))
                return copy_pipe_to_iter(addr, bytes, i);
+       if (iter_is_iovec(i))
+               might_fault();
        iterate_and_advance(i, bytes, v,
-               __copy_to_user(v.iov_base, (from += v.iov_len) - v.iov_len,
-                              v.iov_len),
+               copyout(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len),
                memcpy_to_page(v.bv_page, v.bv_offset,
                               (from += v.bv_len) - v.bv_len, v.bv_len),
                memcpy(v.iov_base, (from += v.iov_len) - v.iov_len, v.iov_len)
@@ -550,18 +571,19 @@ size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 
        return bytes;
 }
-EXPORT_SYMBOL(copy_to_iter);
+EXPORT_SYMBOL(_copy_to_iter);
 
-size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
+size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 {
        char *to = addr;
        if (unlikely(i->type & ITER_PIPE)) {
                WARN_ON(1);
                return 0;
        }
+       if (iter_is_iovec(i))
+               might_fault();
        iterate_and_advance(i, bytes, v,
-               __copy_from_user((to += v.iov_len) - v.iov_len, v.iov_base,
-                                v.iov_len),
+               copyin((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
                memcpy_from_page((to += v.bv_len) - v.bv_len, v.bv_page,
                                 v.bv_offset, v.bv_len),
                memcpy((to += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)
@@ -569,9 +591,9 @@ size_t copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 
        return bytes;
 }
-EXPORT_SYMBOL(copy_from_iter);
+EXPORT_SYMBOL(_copy_from_iter);
 
-bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
+bool _copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
 {
        char *to = addr;
        if (unlikely(i->type & ITER_PIPE)) {
@@ -581,8 +603,10 @@ bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
        if (unlikely(i->count < bytes))
                return false;
 
+       if (iter_is_iovec(i))
+               might_fault();
        iterate_all_kinds(i, bytes, v, ({
-               if (__copy_from_user((to += v.iov_len) - v.iov_len,
+               if (copyin((to += v.iov_len) - v.iov_len,
                                      v.iov_base, v.iov_len))
                        return false;
                0;}),
@@ -594,9 +618,9 @@ bool copy_from_iter_full(void *addr, size_t bytes, struct iov_iter *i)
        iov_iter_advance(i, bytes);
        return true;
 }
-EXPORT_SYMBOL(copy_from_iter_full);
+EXPORT_SYMBOL(_copy_from_iter_full);
 
-size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
+size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 {
        char *to = addr;
        if (unlikely(i->type & ITER_PIPE)) {
@@ -613,10 +637,10 @@ size_t copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 
        return bytes;
 }
-EXPORT_SYMBOL(copy_from_iter_nocache);
+EXPORT_SYMBOL(_copy_from_iter_nocache);
 
 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
-size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
+size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 {
        char *to = addr;
        if (unlikely(i->type & ITER_PIPE)) {
@@ -634,10 +658,10 @@ size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 
        return bytes;
 }
-EXPORT_SYMBOL_GPL(copy_from_iter_flushcache);
+EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
 #endif
 
-bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
+bool _copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
 {
        char *to = addr;
        if (unlikely(i->type & ITER_PIPE)) {
@@ -659,11 +683,22 @@ bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
        iov_iter_advance(i, bytes);
        return true;
 }
-EXPORT_SYMBOL(copy_from_iter_full_nocache);
+EXPORT_SYMBOL(_copy_from_iter_full_nocache);
+
+static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
+{
+       size_t v = n + offset;
+       if (likely(n <= v && v <= (PAGE_SIZE << compound_order(page))))
+               return true;
+       WARN_ON(1);
+       return false;
+}
 
 size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
                         struct iov_iter *i)
 {
+       if (unlikely(!page_copy_sane(page, offset, bytes)))
+               return 0;
        if (i->type & (ITER_BVEC|ITER_KVEC)) {
                void *kaddr = kmap_atomic(page);
                size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
@@ -679,13 +714,15 @@ EXPORT_SYMBOL(copy_page_to_iter);
 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
                         struct iov_iter *i)
 {
+       if (unlikely(!page_copy_sane(page, offset, bytes)))
+               return 0;
        if (unlikely(i->type & ITER_PIPE)) {
                WARN_ON(1);
                return 0;
        }
        if (i->type & (ITER_BVEC|ITER_KVEC)) {
                void *kaddr = kmap_atomic(page);
-               size_t wanted = copy_from_iter(kaddr + offset, bytes, i);
+               size_t wanted = _copy_from_iter(kaddr + offset, bytes, i);
                kunmap_atomic(kaddr);
                return wanted;
        } else
@@ -722,7 +759,7 @@ size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
        if (unlikely(i->type & ITER_PIPE))
                return pipe_zero(bytes, i);
        iterate_and_advance(i, bytes, v,
-               __clear_user(v.iov_base, v.iov_len),
+               clear_user(v.iov_base, v.iov_len),
                memzero_page(v.bv_page, v.bv_offset, v.bv_len),
                memset(v.iov_base, 0, v.iov_len)
        )
@@ -735,14 +772,17 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
                struct iov_iter *i, unsigned long offset, size_t bytes)
 {
        char *kaddr = kmap_atomic(page), *p = kaddr + offset;
+       if (unlikely(!page_copy_sane(page, offset, bytes))) {
+               kunmap_atomic(kaddr);
+               return 0;
+       }
        if (unlikely(i->type & ITER_PIPE)) {
                kunmap_atomic(kaddr);
                WARN_ON(1);
                return 0;
        }
        iterate_all_kinds(i, bytes, v,
-               __copy_from_user_inatomic((p += v.iov_len) - v.iov_len,
-                                         v.iov_base, v.iov_len),
+               copyin((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len),
                memcpy_from_page((p += v.bv_len) - v.bv_len, v.bv_page,
                                 v.bv_offset, v.bv_len),
                memcpy((p += v.iov_len) - v.iov_len, v.iov_base, v.iov_len)

diff --git a/lib/usercopy.c b/lib/usercopy.c
index 1b6010a3beb8528a71676e2fdf0cf19924fd889a..f5d9f08ee032f36a19cafa8a2d83f648d326fd97 100644 (file)
--- a/lib/usercopy.c
+++ b/lib/usercopy.c
@@ -6,8 +6,11 @@
 unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
 {
        unsigned long res = n;
-       if (likely(access_ok(VERIFY_READ, from, n)))
+       might_fault();
+       if (likely(access_ok(VERIFY_READ, from, n))) {
+               kasan_check_write(to, n);
                res = raw_copy_from_user(to, from, n);
+       }
        if (unlikely(res))
                memset(to + (n - res), 0, res);
        return res;
@@ -18,8 +21,11 @@ EXPORT_SYMBOL(_copy_from_user);
 #ifndef INLINE_COPY_TO_USER
 unsigned long _copy_to_user(void *to, const void __user *from, unsigned long n)
 {
-       if (likely(access_ok(VERIFY_WRITE, to, n)))
+       might_fault();
+       if (likely(access_ok(VERIFY_WRITE, to, n))) {
+               kasan_check_read(from, n);
                n = raw_copy_to_user(to, from, n);
+       }
        return n;
 }
 EXPORT_SYMBOL(_copy_to_user);