From: Xishi Qiu qiuxishi@huawei.com
The shadow which correspond 16 bytes memory may span 2 or 3 bytes. If the memory is aligned on 8, then the shadow takes only 2 bytes. So we check "shadow_first_bytes" is enough, and need not to call "memory_is_poisoned_1(addr + 15);". But the code "if (likely(!last_byte))" is wrong judgement.
e.g. addr=0, so last_byte = 15 & KASAN_SHADOW_MASK = 7, then the code will continue to call "memory_is_poisoned_1(addr + 15);"
Signed-off-by: Xishi Qiu qiuxishi@huawei.com Acked-by: Andrey Ryabinin aryabinin@virtuozzo.com Cc: Andrey Konovalov adech.fo@gmail.com Cc: Rusty Russell rusty@rustcorp.com.au Cc: Michal Marek mmarek@suse.cz Cc: zhongjiang@huawei.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org (cherry picked from commit 8d77a6d18ae9ccfd5eee1cc551ee4ac27fd41464) Signed-off-by: Alex Shi alex.shi@linaro.org --- mm/kasan/kasan.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c index 6c513a6..3d64922 100644 --- a/mm/kasan/kasan.c +++ b/mm/kasan/kasan.c @@ -135,12 +135,11 @@ static __always_inline bool memory_is_poisoned_16(unsigned long addr)
if (unlikely(*shadow_addr)) { u16 shadow_first_bytes = *(u16 *)shadow_addr; - s8 last_byte = (addr + 15) & KASAN_SHADOW_MASK;
if (unlikely(shadow_first_bytes)) return true;
- if (likely(!last_byte)) + if (likely(IS_ALIGNED(addr, 8))) return false;
return memory_is_poisoned_1(addr + 15);