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[SCSI] Avoid dangling pointer in scsi_requeue_command() 

When we call scsi_unprep_request() the command associated with the request
gets destroyed and therefore drops its reference on the device.  If this was
the only reference, the device may get released and we end up with a NULL
pointer deref when we call blk_requeue_request.

Reported-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Reviewed-by: Tejun Heo <tj@kernel.org>
Cc: <stable@kernel.org>
[jejb: enhance commend and add commit log for stable]
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Bart Van Assche 2012-06-29 15:34:26 +00:00 committed by James Bottomley
parent 67bd941300
commit 940f5d47e2
1 changed files with 11 additions and 0 deletions
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11
drivers/scsi/scsi_lib.c
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@ -479,15 +479,26 @@ void scsi_requeue_run_queue(struct work_struct *work)
*/
static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
{
struct scsi_device *sdev = cmd->device;
struct request *req = cmd->request;
unsigned long flags;
/*
* We need to hold a reference on the device to avoid the queue being
* killed after the unlock and before scsi_run_queue is invoked which
* may happen because scsi_unprep_request() puts the command which
* releases its reference on the device.
*/
get_device(&sdev->sdev_gendev);
spin_lock_irqsave(q->queue_lock, flags);
scsi_unprep_request(req);
blk_requeue_request(q, req);
spin_unlock_irqrestore(q->queue_lock, flags);
scsi_run_queue(q);
put_device(&sdev->sdev_gendev);
}
void scsi_next_command(struct scsi_cmnd *cmd)