Re: [PATCH v8 1/4] usb: gadget: uvc: prevent use of disabled endpoint

[Avichal Rakesh <arakesh@google.com>]

On 10/24/23 11:36, Avichal Rakesh wrote:
> 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/20230615171558.GK741@pendragon.ideasonboard.com/
> Link: https://lore.kernel.org/20230531085544.253363-1-dan.scally@ideasonboard.com/
> Reviewed-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
> Tested-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
> Signed-off-by: Avichal Rakesh <arakesh@google.com>
> ---
> v1 -> v2: Rebased to ToT and reworded commit message.
> v2 -> v3: Fix email threading goof-up
> v3 -> v4: Address review comments & re-rebase to ToT
> v4 -> v5: Add Reviewed-by & Tested-by
> v5 -> v6: No change
> v6 -> v7: No change
> v7 -> v8: No change. Getting back in review queue
> 
>  drivers/usb/gadget/function/f_uvc.c     | 11 +++++------
>  drivers/usb/gadget/function/f_uvc.h     |  2 +-
>  drivers/usb/gadget/function/uvc.h       |  2 +-
>  drivers/usb/gadget/function/uvc_v4l2.c  | 20 +++++++++++++++++---
>  drivers/usb/gadget/function/uvc_video.c |  3 ++-
>  5 files changed, 26 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
> index faa398109431..ae08341961eb 100644
> --- a/drivers/usb/gadget/function/f_uvc.c
> +++ b/drivers/usb/gadget/function/f_uvc.c
> @@ -263,10 +263,13 @@ uvc_function_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
>  	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);
>  }
> 
> @@ -337,15 +340,11 @@ uvc_function_set_alt(struct usb_function *f, unsigned interface, unsigned alt)
>  		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)
> diff --git a/drivers/usb/gadget/function/f_uvc.h b/drivers/usb/gadget/function/f_uvc.h
> index 1db972d4beeb..e7f9f13f14dc 100644
> --- a/drivers/usb/gadget/function/f_uvc.h
> +++ b/drivers/usb/gadget/function/f_uvc.h
> @@ -11,7 +11,7 @@
> 
>  struct uvc_device;
> 
> -void uvc_function_setup_continue(struct uvc_device *uvc);
> +void uvc_function_setup_continue(struct uvc_device *uvc, int disale_ep);
> 
>  void uvc_function_connect(struct uvc_device *uvc);
> 
> diff --git a/drivers/usb/gadget/function/uvc.h b/drivers/usb/gadget/function/uvc.h
> index 6751de8b63ad..989bc6b4e93d 100644
> --- a/drivers/usb/gadget/function/uvc.h
> +++ b/drivers/usb/gadget/function/uvc.h
> @@ -177,7 +177,7 @@ struct uvc_file_handle {
>   * 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);
> 
> diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c
> index 3f0a9795c0d4..7cb8d027ff0c 100644
> --- a/drivers/usb/gadget/function/uvc_v4l2.c
> +++ b/drivers/usb/gadget/function/uvc_v4l2.c
> @@ -451,7 +451,7 @@ uvc_v4l2_streamon(struct file *file, void *fh, enum v4l2_buf_type type)
>  	 * 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;
> @@ -463,11 +463,18 @@ uvc_v4l2_streamoff(struct file *file, void *fh, enum v4l2_buf_type type)
>  	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
> @@ -500,6 +507,14 @@ uvc_v4l2_subscribe_event(struct v4l2_fh *fh,
>  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;
> @@ -647,4 +662,3 @@ const struct v4l2_file_operations uvc_v4l2_fops = {
>  	.get_unmapped_area = uvcg_v4l2_get_unmapped_area,
>  #endif
>  };
> -
> diff --git a/drivers/usb/gadget/function/uvc_video.c b/drivers/usb/gadget/function/uvc_video.c
> index 91af3b1ef0d4..c334802ac0a4 100644
> --- a/drivers/usb/gadget/function/uvc_video.c
> +++ b/drivers/usb/gadget/function/uvc_video.c
> @@ -384,13 +384,14 @@ static void uvcg_video_pump(struct work_struct *work)
>  	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.
> --
> 2.42.0.758.gaed0368e0e-goog

Hey Greg,

Considering Laurent and Dan haven't responded, and Michael and I have 
tested this change, would it be possible to merge this patch set
if the changes look OK to you? I don't think there are any outstanding
items to be done around these fixes.

Thank you!
- Avi.