linux-kernel - Re: [SCSI] NULL pointer dereference in sym53c8xx (bisected)

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Message-ID: <4EDBAF99.6010904@gentoo.org>
Date:	Sun, 04 Dec 2011 19:36:25 +0200
From:	Stratos Psomadakis <psomas@...too.org>
To:	linux-kernel@...r.kernel.org
CC:	Steffen Maier <maier@...ux.vnet.ibm.com>, stable@...r.kernel.org,
	gregkh@...e.de, linux-scsi@...r.kernel.org,
	JBottomley@...allels.com, matthew@....cx, Martin.vGagern@....net,
	kernel@...too.org
Subject: Re: [SCSI] NULL pointer dereference in sym53c8xx (bisected)

On 12/04/2011 02:11 AM, Stratos Psomadakis wrote:
> On 12/03/2011 11:07 PM, Steffen Maier wrote:
>> On 12/02/2011 04:26 PM, Stratos Psomadakis wrote:
>>> After upstream commit 4e6c82b3614a18740ef63109d58743a359266daf ([SCSI]
>>> fix WARNING: at drivers/scsi/scsi_lib.c:1704), which is also included in
>>> 3.0-stable and 3.1-stable kernels, the kernel fails to boot (NULL
>>> pointer dereference in sym53c8xx_slave_destroy).
>>>
>>> Bug report at the Gentoo Bugzilla (reported and bisected by Martin von
>>> Gagern). [1]  (stack trace [2])
>>>
>>> I think that the problem is that (after commit 4e6c82b)
>>> __scsi_remove_device() is called if slave_alloc() in scsi_alloc_sdev()
>>> fails. But __scsi_remove_device() calls slave_destroy(), which (I think)
>>> doesn't make much sense (ie to call slave_destroy() when slave_alloc()
>>> fails).
>>>
>>> For sym53c8xx, this results in a NULL pointer dereference (struct
>>> sym_lcb pointer) in slave_destroy().
>>>
>>> [1] https://bugs.gentoo.org/show_bug.cgi?id=392567
>>> [2] https://392567.bugs.gentoo.org/attachment.cgi?id=294381
>> To me this looks like the same thing we encountered in the zfcp LLD:
>> http://www.spinics.net/lists/linux-scsi/msg55575.html
>> James explained the pairing of slave_alloc and slave_destroy even if
>> slave_alloc returned early in which case slave_destroy needs to cope
>> with that:
>> http://www.spinics.net/lists/linux-scsi/msg55449.html
>>
> Indeed.
>
> I'll follow-up with a patch similar to the one you sent for zfcp. I
> think that returning if sym_lcb is NULL should be ok.
I forgot to chain the patch email in this thread, so here's the link:
http://marc.info/?l=linux-scsi&m=132295936832641&w=2

>> HTH
>> Steffen
>>
>> Linux on System z Development
>>
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-- 
Stratos Psomadakis
<psomas@...too.org>



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