USB: gadget: f_midi: f_midi_complete to call queue_work

BugLink: https://bugs.launchpad.net/bugs/2106494

[ Upstream commit 4ab37fc ]

When using USB MIDI, a lock is attempted to be acquired twice through a
re-entrant call to f_midi_transmit, causing a deadlock.

Fix it by using queue_work() to schedule the inner f_midi_transmit() via
a high priority work queue from the completion handler.

Link: https://lore.kernel.org/all/CAArt=LjxU0fUZOj06X+5tkeGT+6RbXzpWg1h4t4Fwa_KGVAX6g@mail.gmail.com/
Fixes: d5daf49 ("USB: gadget: midi: add midi function driver")
Cc: stable <[email protected]>
Signed-off-by: Jill Donahue <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
Signed-off-by: Noah Wager <[email protected]>
Signed-off-by: Mehmet Basaran <[email protected]>

Author: jilliandonahue

drivers/usb/gadget/function/f_midi.c

@@ -283,7 +283,7 @@ f_midi_complete(struct usb_ep *ep, struct usb_request *req)
 			/* Our transmit completed. See if there's more to go.
 			 * f_midi_transmit eats req, don't queue it again. */
 			req->length = 0;
-			f_midi_transmit(midi);
+			queue_work(system_highpri_wq, &midi->work);
 			return;
 		}
 		break;