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kasan: fix last shadow judgement in memory_is_poisoned_16() 

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>
This commit is contained in:
Xishi Qiu 2015-09-17 16:01:43 -07:00 committed by Linus Torvalds
parent 3aaf14da80
commit 8d77a6d18a
1 changed files with 1 additions and 2 deletions
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3
mm/kasan/kasan.c
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@ -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);