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

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

1 files changed, 69 insertions, 29 deletions

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index c9a69064462f..52c8dd6d8e82 100644
--- 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)