gadgetfs: ep_io - wait until IRQ finishes

after usb_ep_queue() if wait_for_completion_interruptible() is
interrupted we need to wait until IRQ gets finished.

Otherwise complete() from epio_complete() can corrupt stack.
Signed-off-by: Jozef Martiniak <jomajm@gmail.com>
Link: https://lore.kernel.org/r/20220708070645.6130-1-jomajm@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/legacy/inode.c

@@ -362,6 +362,7 @@ ep_io (struct ep_data *epdata, void *buf, unsigned len)
 				spin_unlock_irq (&epdata->dev->lock);
 
 				DBG (epdata->dev, "endpoint gone\n");
+				wait_for_completion(&done);
 				epdata->status = -ENODEV;
 			}
 		}