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authorPeter Collingbourne <pcc@google.com>2021-04-29 22:59:46 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-04-30 11:20:41 -0700
commitbfcfe37136d718f5f5846f51df9ff22d13752a5b (patch)
tree6c11742772238ae94b78e091955a9b750c15c5f9 /mm/kasan
parentf76e0c41c0ac7f6ae614dd50ce3e983b974b87c1 (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.h3
-rw-r--r--mm/kasan/sw_tags.c10
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) \