From 425f11f628631c26ebc4dfe0dabb77e0eb4643af Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Fri, 29 Jun 2012 15:34:26 +0000 Subject: 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: Paul Gortmaker --- drivers/scsi/scsi_lib.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 6712297407bb..a7e6572940ef 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -484,15 +484,26 @@ static void scsi_run_queue(struct request_queue *q) */ 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