linux-kernel - Re: use after free of struct powernow_k8

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Date:	Wed, 30 Sep 2009 13:30:59 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Michal Schmidt <mschmidt@...hat.com>
Cc:	linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org,
	mark.langsdorf@....com
Subject: Re: use after free of struct powernow_k8_data

On Thu, 24 Sep 2009 16:51:25 +0200
Michal Schmidt <mschmidt@...hat.com> wrote:

> Hello,
> 
> After resume from suspend I get:
> 
> =============================================================================
> BUG kmalloc-256: Poison overwritten
> -----------------------------------------------------------------------------
> 
> INFO: 0xffff880073bf1bb0-0xffff880073bf1bb7. First byte 0x12 instead of 0x6b
> INFO: Allocated in powernowk8_cpu_init+0x72/0xc27 [powernow_k8] age=290 cpu=0 pid=1782
> INFO: Freed in powernowk8_cpu_exit+0x6b/0x88 [powernow_k8] age=289 cpu=0 pid=1782
> INFO: Slab 0xffffea0002f059e8 objects=12 used=10 fp=0xffff880073bf1b88 flags=0x200000000000c3
> INFO: Object 0xffff880073bf1b88 @offset=2952 fp=0xffff880073bf1e18
> 
> Bytes b4 0xffff880073bf1b78:  ec 77 fe ff 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a __w____....ZZZZZZZZ
>   Object 0xffff880073bf1b88:  6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
>   Object 0xffff880073bf1b98:  6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
>   Object 0xffff880073bf1ba8:  6b 6b 6b 6b 6b 6b 6b 6b 12 00 00 00 0c 00 00 00 kkkkkkkk........
>   Object 0xffff880073bf1bb8:  6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
> 
> The overwritten values correspond to the currvid (0x12) and currfid (0x0c)
> fields if struct powernow_k8_data. Earlier in dmesg these exact values
> can be seen:
> 
> powernow-k8: table matched fid 0xc, giving vid 0x12
> powernow-k8: target matches current values (fid 0xc, vid 0x12)
> 
> It seems that something called query_current_values_with_pending_wait()
> while the struct was already freed.
> 
> It is perfectly reproducible. The kernel is the latest from git
> (94a8d5caba74211ec76dac80fc6e2d5c391530df).
> I'm attaching the full dmesg and .config.
> 

Do you know if this is a regression?  If so, since which kernel version?

Thanks.
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