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Subject: Re: [patch 4/4] change slab poison pattern
From: Pekka Enberg <penberg@cs.helsinki.fi>
To: Akinobu Mita <mita@miraclelinux.com>
Cc: linux-kernel@vger.kernel.org, akpm@osdl.org,
       Matt Mackall <mpm@selenic.com>,
       Manfred Spraul <manfred@colorfullife.com>
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Date: Mon, 24 Apr 2006 12:20:03 +0300
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Hi,

On Mon, 2006-04-24 at 16:33 +0800, Akinobu Mita wrote:
> kref debugging cannot detect kref_put() with unreferenced object,
> when the structure including kref is allocated by slab
> and slab debugging config is enabled.
> 
> Because use-after-free poisoning make kref counter signed value.
> So this patch prevents it by changing poisoning pattern.

Then why not check against POISON_INUSE when CONFIG_SLAB_DEBUG in the
kref debugging code? I would prefer you didn't change the slab constants
(they're well known by everyone now) but if you must, at least stick a
big fat comment there.

			Pekka