linux-kernel - Re: 2.6.39-rc5+ BUG at scsi_run

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Date:	Tue, 03 May 2011 12:00:18 -0500
From:	James Bottomley <James.Bottomley@...e.de>
To:	Jim Schutt <jaschut@...dia.gov>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: 2.6.39-rc5+ BUG at scsi_run_queue+0x24/0xe3

On Tue, 2011-05-03 at 10:53 -0600, Jim Schutt wrote:
> Please let me know if what further information you need, or if there is
> anything I can do, to help resolve this.

I think this is the fix (already in rc-fixes):

James

---
>From 3e85ea868dbd60a84240be5c1eebc36841b9c568 Mon Sep 17 00:00:00 2001
From: James Bottomley <James.Bottomley@...e.de>
Date: Sun, 1 May 2011 09:42:07 -0500
Subject: [PATCH] [SCSI] fix oops in scsi_run_queue()

The recent commit closing the race window in device teardown:

commit 86cbfb5607d4b81b1a993ff689bbd2addd5d3a9b
Author: James Bottomley <James.Bottomley@...e.de>
Date:   Fri Apr 22 10:39:59 2011 -0500

    [SCSI] put stricter guards on queue dead checks

is causing a potential NULL deref in scsi_run_queue() because the
q->queuedata may already be NULL by the time this function is called.
Since we shouldn't be running a queue that is being torn down, simply
add a NULL check in scsi_run_queue() to forestall this.

Signed-off-by: James Bottomley <James.Bottomley@...e.de>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index e9901b8..03979f4 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -404,6 +404,10 @@ static void scsi_run_queue(struct request_queue *q)
 	LIST_HEAD(starved_list);
 	unsigned long flags;
 
+	/* if the device is dead, sdev will be NULL, so no queue to run */
+	if (!sdev)
+		return;
+
 	if (scsi_target(sdev)->single_lun)
 		scsi_single_lun_run(sdev);
 


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