usb: gadget: uvc: Fix error handling in uvc_queue_buffer()

commit ebe864a6 upstream.

The conversion to videobuf2 failed to check the return value of
vb2_qbuf(). Fix it.
Reported-by: Michael Grzeschik <mgr@pengutronix.de>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-By: Michael Grzeschik <mgr@pengutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/uvc_queue.c

@@ -177,12 +177,16 @@ static int uvc_queue_buffer(struct uvc_video_queue *queue,
 
 	mutex_lock(&queue->mutex);
 	ret = vb2_qbuf(&queue->queue, buf);
+	if (ret < 0)
+		goto done;
+
 	spin_lock_irqsave(&queue->irqlock, flags);
 	ret = (queue->flags & UVC_QUEUE_PAUSED) != 0;
 	queue->flags &= ~UVC_QUEUE_PAUSED;
 	spin_unlock_irqrestore(&queue->irqlock, flags);
-	mutex_unlock(&queue->mutex);
 
+done:
+	mutex_unlock(&queue->mutex);
 	return ret;
 }