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Subject[34-longterm 169/196] fix oops in scsi_run_queue()
Date
From: James Bottomley <James.Bottomley@suse.de>

-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.
-------------------
commit c055f5b2614b4f758ae6cc86733f31fa4c2c5844 upstream.

The recent commit closing the race window in device teardown:

commit 86cbfb5607d4b81b1a993ff689bbd2addd5d3a9b
Author: James Bottomley <James.Bottomley@suse.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.

Tested-by: Jim Schutt <jaschut@sandia.gov>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
drivers/scsi/scsi_lib.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index c2a9e12..725f3cd 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -400,10 +400,15 @@ static inline int scsi_host_is_busy(struct Scsi_Host *shost)
static void scsi_run_queue(struct request_queue *q)
{
struct scsi_device *sdev = q->queuedata;
- struct Scsi_Host *shost = sdev->host;
+ struct Scsi_Host *shost;
LIST_HEAD(starved_list);
unsigned long flags;

+ /* if the device is dead, sdev will be NULL, so no queue to run */
+ if (!sdev)
+ return;
+
+ shost = sdev->host;
if (scsi_target(sdev)->single_lun)
scsi_single_lun_run(sdev);

--
1.7.9.3


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