linux-kernel - Re: [PATCH] mm, kasan: introduce a special shadow value for allocator metadata

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Date:	Tue, 31 May 2016 14:52:49 +0300
From:	Andrey Ryabinin <aryabinin@...tuozzo.com>
To:	Alexander Potapenko <glider@...gle.com>, <adech.fo@...il.com>,
	<cl@...ux.com>, <dvyukov@...gle.com>, <akpm@...ux-foundation.org>,
	<rostedt@...dmis.org>, <iamjoonsoo.kim@....com>,
	<js1304@...il.com>, <kcc@...gle.com>
CC:	<kasan-dev@...glegroups.com>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm, kasan: introduce a special shadow value for allocator
 metadata



On 05/31/2016 01:44 PM, Alexander Potapenko wrote:
> Add a special shadow value to distinguish accesses to KASAN-specific
> allocator metadata.
> 
> Unlike AddressSanitizer in the userspace, KASAN lets the kernel proceed
> after a memory error. However a write to the kmalloc metadata may cause
> memory corruptions that will make the tool itself unreliable and induce
> crashes later on. Warning about such corruptions will ease the
> debugging.

It will not. Whether out-of-bounds hits metadata or not is absolutely irrelevant
to the bug itself. This information doesn't help to understand, analyze or fix the bug.