From 84ecccfc25f7dda4f1d2aeb6db0658368d3ef185 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Fri, 29 Jun 2012 15:34:26 +0000 Subject: SCSI: Avoid dangling pointer in scsi_requeue_command() commit 940f5d47e2f2e1fa00443921a0abf4822335b54d upstream. 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 Signed-off-by: Bart Van Assche Reviewed-by: Mike Christie Reviewed-by: Tejun Heo [jejb: enhance commend and add commit log for stable] Signed-off-by: James Bottomley Signed-off-by: Greg Kroah-Hartman --- drivers/scsi/scsi_lib.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'drivers/scsi') diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index f97edb75e56..19291463c55 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -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) -- cgit v1.2.3-18-g5258