linux-kernel - [PATCH v2] kasan: Fix a type conversion error

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Date:	Wed, 9 Sep 2015 11:04:05 +0000
From:	Wang Long <long.wanglong@...wei.com>
To:	<ryabinin.a.a@...il.com>, <adech.fo@...il.com>
CC:	<akpm@...ux-foundation.org>, <rusty@...tcorp.com.au>,
	<long.wanglong@...wei.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>, <wanglong@...qinren.net>,
	<peifeiyue@...wei.com>, <morgan.wang@...wei.com>
Subject: [PATCH v2] kasan: Fix a type conversion error

The current KASAN code can not find the following out-of-bounds
bugs:
	char *ptr;
	ptr = kmalloc(8, GFP_KERNEL);
	memset(ptr+7, 0, 2);

the cause of the problem is the type conversion error in
*memory_is_poisoned_n* function. So this patch fix that.

Signed-off-by: Wang Long <long.wanglong@...wei.com>
Acked-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
---
 mm/kasan/kasan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c
index 7b28e9c..5d65d06 100644
--- a/mm/kasan/kasan.c
+++ b/mm/kasan/kasan.c
@@ -204,7 +204,7 @@ static __always_inline bool memory_is_poisoned_n(unsigned long addr,
 		s8 *last_shadow = (s8 *)kasan_mem_to_shadow((void *)last_byte);
 
 		if (unlikely(ret != (unsigned long)last_shadow ||
-			((last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
+			((long)(last_byte & KASAN_SHADOW_MASK) >= *last_shadow)))
 			return true;
 	}
 	return false;
-- 
1.8.3.4

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