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 --cc include/linux/uio.h
index 55cd54a0e94100cc71b4ddeb03d8b35392a32b7a,243e2362fe1a8a1ea8b0480c362d10c679d4ea95..342d2dc225b95b51e36d0f9a8a37c990e69f4d74
--- 1/include/linux/uio.h
--- 2/include/linux/uio.h
+++ b/include/linux/uio.h
@@@ -91,26 -92,58 +92,79 @@@ size_t copy_page_to_iter(struct page *p
                         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
 + * copy_from_iter_flushcache() than copy_from_iter_nocache() must check for
 + * 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 --cc lib/iov_iter.c
index c9a69064462f8c0bf3b1a7b58623c14e7b0d371f,b3b2ee8a20b54ac597046bd1dfd5c3a6d9627c46..52c8dd6d8e8290fa8df614e0017542a600b9c536
--- 1/lib/iov_iter.c
--- 2/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@@ -613,31 -637,9 +637,31 @@@ size_t _copy_from_iter_nocache(void *ad
  
        return bytes;
  }
- EXPORT_SYMBOL(copy_from_iter_nocache);
+ EXPORT_SYMBOL(_copy_from_iter_nocache);
  
- size_t copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 +#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
- EXPORT_SYMBOL_GPL(copy_from_iter_flushcache);
++size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 +{
 +      char *to = addr;
 +      if (unlikely(i->type & ITER_PIPE)) {
 +              WARN_ON(1);
 +              return 0;
 +      }
 +      iterate_and_advance(i, bytes, v,
 +              __copy_from_user_flushcache((to += v.iov_len) - v.iov_len,
 +                                       v.iov_base, v.iov_len),
 +              memcpy_page_flushcache((to += v.bv_len) - v.bv_len, v.bv_page,
 +                               v.bv_offset, v.bv_len),
 +              memcpy_flushcache((to += v.iov_len) - v.iov_len, v.iov_base,
 +                      v.iov_len)
 +      )
 +
 +      return bytes;
 +}
- bool copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
++EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
 +#endif
 +
+ bool _copy_from_iter_full_nocache(void *addr, size_t bytes, struct iov_iter *i)
  {
        char *to = addr;
        if (unlikely(i->type & ITER_PIPE)) {