usb: gadget: uvc: prevent use of disabled endpoint

Currently the set_alt callback immediately disables the endpoint and queues
the v4l2 streamoff event. However, as the streamoff event is processed
asynchronously, it is possible that the video_pump thread attempts to queue
requests to an already disabled endpoint.

This change moves disabling usb endpoint to the end of streamoff event
callback. As the endpoint's state can no longer be used, video_pump is
now guarded by uvc->state as well. To be consistent with the actual
streaming state, uvc->state is now toggled between CONNECTED and STREAMING
from the v4l2 event callback only.

Link: https://lore.kernel.org/[e-mail]/
Link: https://lore.kernel.org/[e-mail]/
Reviewed-by: Daniel Scally <[e-mail]>
Reviewed-by: Michael Grzeschik <[e-mail]>
Tested-by: Michael Grzeschik <[e-mail]>
Signed-off-by: Avichal Rakesh <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/gadget/function/f_uvc.c

···
 	return 0;
 }
 
-void uvc_function_setup_continue(struct uvc_device *uvc)
+void uvc_function_setup_continue(struct uvc_device *uvc, int disable_ep)
 {
 	struct usb_composite_dev *cdev = uvc->func.config->cdev;
+
+	if (disable_ep && uvc->video.ep)
+		usb_ep_disable(uvc->video.ep);
 
 	usb_composite_setup_continue(cdev);
 }
···
 		if (uvc->state != UVC_STATE_STREAMING)
 			return 0;
 
-		if (uvc->video.ep)
-			usb_ep_disable(uvc->video.ep);
-
 		memset(&v4l2_event, 0, sizeof(v4l2_event));
 		v4l2_event.type = UVC_EVENT_STREAMOFF;
 		v4l2_event_queue(&uvc->vdev, &v4l2_event);
 
-		uvc->state = UVC_STATE_CONNECTED;
-		return 0;
+		return USB_GADGET_DELAYED_STATUS;
 
 	case 1:
 		if (uvc->state != UVC_STATE_CONNECTED)

drivers/usb/gadget/function/f_uvc.h

···
 
 struct uvc_device;
 
-void uvc_function_setup_continue(struct uvc_device *uvc);
+void uvc_function_setup_continue(struct uvc_device *uvc, int disable_ep);
 
 void uvc_function_connect(struct uvc_device *uvc);
 

drivers/usb/gadget/function/uvc.h

···
  * Functions
  */
 
-extern void uvc_function_setup_continue(struct uvc_device *uvc);
+extern void uvc_function_setup_continue(struct uvc_device *uvc, int disable_ep);
 extern void uvc_function_connect(struct uvc_device *uvc);
 extern void uvc_function_disconnect(struct uvc_device *uvc);
 

drivers/usb/gadget/function/uvc_v4l2.c

···
 	 * Complete the alternate setting selection setup phase now that
 	 * userspace is ready to provide video frames.
 	 */
-	uvc_function_setup_continue(uvc);
+	uvc_function_setup_continue(uvc, 0);
 	uvc->state = UVC_STATE_STREAMING;
 
 	return 0;
···
 	struct video_device *vdev = video_devdata(file);
 	struct uvc_device *uvc = video_get_drvdata(vdev);
 	struct uvc_video *video = &uvc->video;
+	int ret = 0;
 
 	if (type != video->queue.queue.type)
 		return -EINVAL;
 
-	return uvcg_video_enable(video, 0);
+	uvc->state = UVC_STATE_CONNECTED;
+	ret = uvcg_video_enable(video, 0);
+	if (ret < 0)
+		return ret;
+
+	uvc_function_setup_continue(uvc, 1);
+	return 0;
 }
 
 static int
···
 static void uvc_v4l2_disable(struct uvc_device *uvc)
 {
 	uvc_function_disconnect(uvc);
+	/*
+	 * Drop uvc->state to CONNECTED if it was streaming before.
+	 * This ensures that the usb_requests are no longer queued
+	 * to the controller.
+	 */
+	if (uvc->state == UVC_STATE_STREAMING)
+		uvc->state = UVC_STATE_CONNECTED;
+
 	uvcg_video_enable(&uvc->video, 0);
 	uvcg_free_buffers(&uvc->video.queue);
 	uvc->func_connected = false;
···
 	.get_unmapped_area = uvcg_v4l2_get_unmapped_area,
 #endif
 };
-

drivers/usb/gadget/function/uvc_video.c

···
 	struct uvc_video_queue *queue = &video->queue;
 	/* video->max_payload_size is only set when using bulk transfer */
 	bool is_bulk = video->max_payload_size;
+	struct uvc_device *uvc = video->uvc;
 	struct usb_request *req = NULL;
 	struct uvc_buffer *buf;
 	unsigned long flags;
 	bool buf_done;
 	int ret;
 
-	while (video->ep->enabled) {
+	while (uvc->state == UVC_STATE_STREAMING && video->ep->enabled) {
 		/*
 		 * Retrieve the first available USB request, protected by the
 		 * request lock.