linux-kernel - Re: [PATCH V2] kasan: fix last shadow judgement in memory_is_poisoned

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Date:	Wed, 9 Sep 2015 13:01:34 +0300
From:	Andrey Ryabinin <aryabinin@...tuozzo.com>
To:	Xishi Qiu <qiuxishi@...wei.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrey Konovalov <adech.fo@...il.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Michal Marek <mmarek@...e.cz>, <zhongjiang@...wei.com>
CC:	Linux MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
	<ryabinin.a.a@...il.com>
Subject: Re: [PATCH V2] kasan: fix last shadow judgement in
 memory_is_poisoned_16()

On 09/08/2015 03:12 PM, Xishi Qiu wrote:
> 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@...wei.com>

Acked-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
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