diff options
| author | Peter Collingbourne <pcc@google.com> | 2021-04-29 22:59:46 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-04-30 11:20:41 -0700 |
| commit | bfcfe37136d718f5f5846f51df9ff22d13752a5b (patch) | |
| tree | 6c11742772238ae94b78e091955a9b750c15c5f9 /mm/kasan | |
| parent | f76e0c41c0ac7f6ae614dd50ce3e983b974b87c1 (diff) | |
kasan: fix kasan_byte_accessible() to be consistent with actual checks
We can sometimes end up with kasan_byte_accessible() being called on
non-slab memory. For example ksize() and krealloc() may end up calling it
on KFENCE allocated memory. In this case the memory will be tagged with
KASAN_SHADOW_INIT, which a subsequent patch ("kasan: initialize shadow to
TAG_INVALID for SW_TAGS") will set to the same value as KASAN_TAG_INVALID,
causing kasan_byte_accessible() to fail when called on non-slab memory.
This highlighted the fact that the check in kasan_byte_accessible() was
inconsistent with checks as implemented for loads and stores
(kasan_check_range() in SW tags mode and hardware-implemented checks in HW
tags mode). kasan_check_range() does not have a check for
KASAN_TAG_INVALID, and instead has a comparison against
KASAN_SHADOW_START. In HW tags mode, we do not have either, but we do set
TCR_EL1.TCMA which corresponds with the comparison against
KASAN_TAG_KERNEL.
Therefore, update kasan_byte_accessible() for both SW and HW tags modes to
correspond with the respective checks on loads and stores.
Link: https://linux-review.googlesource.com/id/Ic6d40803c57dcc6331bd97fbb9a60b0d38a65a36
Link: https://lkml.kernel.org/r/20210405220647.1965262-1-pcc@google.com
Signed-off-by: Peter Collingbourne <pcc@google.com>
Reviewed-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Peter Collingbourne <pcc@google.com>
Cc: Evgenii Stepanov <eugenis@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/kasan')
| -rw-r--r-- | mm/kasan/kasan.h | 3 | ||||
| -rw-r--r-- | mm/kasan/sw_tags.c | 10 |
2 files changed, 8 insertions, 5 deletions
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index c1581e8a9b8e..552f8381d988 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -396,8 +396,7 @@ static inline bool kasan_byte_accessible(const void *addr) u8 ptr_tag = get_tag(addr); u8 mem_tag = hw_get_mem_tag((void *)addr); - return (mem_tag != KASAN_TAG_INVALID) && - (ptr_tag == KASAN_TAG_KERNEL || ptr_tag == mem_tag); + return ptr_tag == KASAN_TAG_KERNEL || ptr_tag == mem_tag; } #else /* CONFIG_KASAN_HW_TAGS */ diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c index 94c2d33be333..00ae8913fc74 100644 --- a/mm/kasan/sw_tags.c +++ b/mm/kasan/sw_tags.c @@ -121,10 +121,14 @@ bool kasan_check_range(unsigned long addr, size_t size, bool write, bool kasan_byte_accessible(const void *addr) { u8 tag = get_tag(addr); - u8 shadow_byte = READ_ONCE(*(u8 *)kasan_mem_to_shadow(kasan_reset_tag(addr))); + void *untagged_addr = kasan_reset_tag(addr); + u8 shadow_byte; - return (shadow_byte != KASAN_TAG_INVALID) && - (tag == KASAN_TAG_KERNEL || tag == shadow_byte); + if (untagged_addr < kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) + return false; + + shadow_byte = READ_ONCE(*(u8 *)kasan_mem_to_shadow(untagged_addr)); + return tag == KASAN_TAG_KERNEL || tag == shadow_byte; } #define DEFINE_HWASAN_LOAD_STORE(size) \ |