linux-kernel - Re: [PATCH] fix NULL-pointer dereference on scsi_run

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Message-ID: <1343897839.5073.7.camel@dabdike.int.hansenpartnership.com>
Date:	Thu, 02 Aug 2012 09:57:19 +0100
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Chanho Min <chanho0207@...il.com>
Cc:	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] fix NULL-pointer dereference on scsi_run_queue

On Thu, 2012-08-02 at 17:41 +0900, Chanho Min wrote:
> This patch is to fix a oops from a torn down device. When
> scsi_run_queue process starved queues, scsi_request_fn can race with
> scsi_remove_device. In this case, rarely, scsi_request_fn release the
> last reference and set sdev->request_queue to NULL. It result in
> NULL-pointer dereference when spin_unlock is tried with (NULL)->
> queue_lock. We need to add an extra reference to the device on both
> sides of the __blk_run_queue to hold reference until scsi_request_fn
> is finished.

You need a recent kernel with this patch:

commit 940f5d47e2f2e1fa00443921a0abf4822335b54d
Author: Bart Van Assche <bvanassche@....org>
Date:   Fri Jun 29 15:34:26 2012 +0000

    [SCSI] Avoid dangling pointer in scsi_requeue_command()

James


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