[SCSI] Avoid dangling pointer in scsi_requeue_command() (940f5d47) · Commits · 戴 / test

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>

drivers/scsi/scsi_lib.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -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)

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