The patch titled
Subject: kasan: fix last shadow judgement in memory_is_poisoned_16()
has been added to the -mm tree. Its filename is
kasan-fix-last-shadow-judgement-in-memory_is_poisoned_16.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kasan-fix-last-shadow-judgement-in-memory_is_poisoned_16.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kasan-fix-last-shadow-judgement-in-memory_is_poisoned_16.patch
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------------------------------------------------------
From: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx>
Acked-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Andrey Konovalov <adech.fo@xxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Michal Marek <mmarek@xxxxxxx>
Cc: <zhongjiang@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kasan/kasan.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff -puN mm/kasan/kasan.c~kasan-fix-last-shadow-judgement-in-memory_is_poisoned_16 mm/kasan/kasan.c
--- a/mm/kasan/kasan.c~kasan-fix-last-shadow-judgement-in-memory_is_poisoned_16
+++ a/mm/kasan/kasan.c
@@ -135,12 +135,11 @@ static __always_inline bool memory_is_po
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);
_
Patches currently in -mm which might be from qiuxishi@xxxxxxxxxx are
kasan-fix-last-shadow-judgement-in-memory_is_poisoned_16.patch
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