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Commit e076da13 authored by Oliver Neukum's avatar Oliver Neukum Committed by Greg Kroah-Hartman
Browse files

UAS: fix deadlock in error handling and PM flushing work 



commit f6cc6093a729ede1ff5658b493237c42b82ba107 upstream.

A SCSI error handler and block runtime PM must not allocate
memory with GFP_KERNEL. Furthermore they must not wait for
tasks allocating memory with GFP_KERNEL.
That means that they cannot share a workqueue with arbitrary tasks.

Fix this for UAS using a private workqueue.

Signed-off-by: default avatarOliver Neukum <oneukum@suse.com>
Fixes: f9dc024a ("uas: pre_reset and suspend: Fix a few races")
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200415141750.811-2-oneukum@suse.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9ca6a4d8

drivers/usb/storage/uas.c

+40 −3
Original line number Diff line number Diff line
@@ -81,6 +81,19 @@ static void uas_free_streams(struct uas_dev_info *devinfo); 
static void uas_log_cmd_state(struct scsi_cmnd *cmnd, const char *prefix,

				int status);



/*

 * This driver needs its own workqueue, as we need to control memory allocation.

 *

 * In the course of error handling and power management uas_wait_for_pending_cmnds()

 * needs to flush pending work items. In these contexts we cannot allocate memory

 * by doing block IO as we would deadlock. For the same reason we cannot wait

 * for anything allocating memory not heeding these constraints.

 *

 * So we have to control all work items that can be on the workqueue we flush.

 * Hence we cannot share a queue and need our own.

 */

static struct workqueue_struct *workqueue;



static void uas_do_work(struct work_struct *work)

{

	struct uas_dev_info *devinfo =
@@ -109,7 +122,7 @@ static void uas_do_work(struct work_struct *work) 
		if (!err)

			cmdinfo->state &= ~IS_IN_WORK_LIST;

		else

			schedule_work(&devinfo->work);

			queue_work(workqueue, &devinfo->work);

	}

out:

	spin_unlock_irqrestore(&devinfo->lock, flags);
@@ -134,7 +147,7 @@ static void uas_add_work(struct uas_cmd_info *cmdinfo) 


	lockdep_assert_held(&devinfo->lock);

	cmdinfo->state |= IS_IN_WORK_LIST;

	schedule_work(&devinfo->work);

	queue_work(workqueue, &devinfo->work);

}



static void uas_zap_pending(struct uas_dev_info *devinfo, int result)
@@ -1236,7 +1249,31 @@ static struct usb_driver uas_driver = { 
	.id_table = uas_usb_ids,

};



module_usb_driver(uas_driver);

static int __init uas_init(void)

{

	int rv;



	workqueue = alloc_workqueue("uas", WQ_MEM_RECLAIM, 0);

	if (!workqueue)

		return -ENOMEM;



	rv = usb_register(&uas_driver);

	if (rv) {

		destroy_workqueue(workqueue);

		return -ENOMEM;

	}



	return 0;

}



static void __exit uas_exit(void)

{

	usb_deregister(&uas_driver);

	destroy_workqueue(workqueue);

}



module_init(uas_init);

module_exit(uas_exit);



MODULE_LICENSE("GPL");

MODULE_AUTHOR(