diff mbox series

[v2,1/2] media: uvcvideo: Fix race condition with usb_kill_urb

Message ID 20221212-uvc-race-v2-1-54496cc3b8ab@chromium.org
State New
Headers
Series uvc: Fix race condition on uvc |

Commit Message

Ricardo Ribalda Dec. 13, 2022, 2:35 p.m. UTC 
  usb_kill_urb warranties that all the handlers are finished when it
returns, but does not protect against threads that might be handling
asynchronously the urb.

For UVC, the function uvc_ctrl_status_event_async() takes care of
control changes asynchronously.

 If the code is executed in the following order:

CPU 0					CPU 1
===== 					=====
uvc_status_complete()
					uvc_status_stop()
uvc_ctrl_status_event_work()
					uvc_status_start() -> FAIL

Then uvc_status_start will keep failing and this error will be shown:

<4>[    5.540139] URB 0000000000000000 submitted while active
drivers/usb/core/urb.c:378 usb_submit_urb+0x4c3/0x528

Let's improve the current situation, by not re-submiting the urb if
we are stopping the status event. Also process the queued work
(if any) during stop.

CPU 0					CPU 1
===== 					=====
uvc_status_complete()
					uvc_status_stop()
					uvc_status_start()
uvc_ctrl_status_event_work() -> FAIL

Hopefully, with the usb layer protection this should be enough to cover
all the cases.

Cc: stable@vger.kernel.org
Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives")
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_ctrl.c   | 3 +++
 drivers/media/usb/uvc/uvc_status.c | 6 ++++++
 drivers/media/usb/uvc/uvcvideo.h   | 1 +
 3 files changed, 10 insertions(+)

Comments

Yunke Cao Dec. 14, 2022, 4:04 a.m. UTC | #1 
On Tue, Dec 13, 2022 at 11:36 PM Ricardo Ribalda <ribalda@chromium.org> wrote:
>
> usb_kill_urb warranties that all the handlers are finished when it
> returns, but does not protect against threads that might be handling
> asynchronously the urb.
>
> For UVC, the function uvc_ctrl_status_event_async() takes care of
> control changes asynchronously.
>
>  If the code is executed in the following order:
>
> CPU 0                                   CPU 1
> =====                                   =====
> uvc_status_complete()
>                                         uvc_status_stop()
> uvc_ctrl_status_event_work()
>                                         uvc_status_start() -> FAIL
>
> Then uvc_status_start will keep failing and this error will be shown:
>
> <4>[    5.540139] URB 0000000000000000 submitted while active
> drivers/usb/core/urb.c:378 usb_submit_urb+0x4c3/0x528
>
> Let's improve the current situation, by not re-submiting the urb if
> we are stopping the status event. Also process the queued work
> (if any) during stop.
>
> CPU 0                                   CPU 1
> =====                                   =====
> uvc_status_complete()
>                                         uvc_status_stop()
>                                         uvc_status_start()
> uvc_ctrl_status_event_work() -> FAIL
>
> Hopefully, with the usb layer protection this should be enough to cover
> all the cases.
>
> Cc: stable@vger.kernel.org
> Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives")
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
>  drivers/media/usb/uvc/uvc_ctrl.c   | 3 +++
>  drivers/media/usb/uvc/uvc_status.c | 6 ++++++
>  drivers/media/usb/uvc/uvcvideo.h   | 1 +
>  3 files changed, 10 insertions(+)
>
> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> index c95a2229f4fa..5160facc8e20 100644
> --- a/drivers/media/usb/uvc/uvc_ctrl.c
> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> @@ -1442,6 +1442,9 @@ static void uvc_ctrl_status_event_work(struct work_struct *work)
>
>         uvc_ctrl_status_event(w->chain, w->ctrl, w->data);
>
> +       if (dev->flush_status)
> +               return;
> +
>         /* Resubmit the URB. */
>         w->urb->interval = dev->int_ep->desc.bInterval;
>         ret = usb_submit_urb(w->urb, GFP_KERNEL);
> diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
> index 7518ffce22ed..09a5802dc974 100644
> --- a/drivers/media/usb/uvc/uvc_status.c
> +++ b/drivers/media/usb/uvc/uvc_status.c
> @@ -304,10 +304,16 @@ int uvc_status_start(struct uvc_device *dev, gfp_t flags)
>         if (dev->int_urb == NULL)
>                 return 0;
>
> +       dev->flush_status = false;
>         return usb_submit_urb(dev->int_urb, flags);
>  }
>
>  void uvc_status_stop(struct uvc_device *dev)
>  {
> +       struct uvc_ctrl_work *w = &dev->async_ctrl;
> +
> +       dev->flush_status = true;
>         usb_kill_urb(dev->int_urb);
> +       if (cancel_work_sync(&w->work))
> +               uvc_ctrl_status_event(w->chain, w->ctrl, w->data);
>  }
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index df93db259312..6a9b72d6789e 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -560,6 +560,7 @@ struct uvc_device {
>         struct usb_host_endpoint *int_ep;
>         struct urb *int_urb;
>         u8 *status;
> +       bool flush_status;
>         struct input_dev *input;
>         char input_phys[64];
>
>
> --
> 2.39.0.rc1.256.g54fd8350bd-goog-b4-0.11.0-dev-696ae

Reviewed-by: Yunke Cao <yunkec@chromium.org>
diff mbox series

Patch

diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
index c95a2229f4fa..5160facc8e20 100644
--- a/drivers/media/usb/uvc/uvc_ctrl.c
+++ b/drivers/media/usb/uvc/uvc_ctrl.c
@@ -1442,6 +1442,9 @@  static void uvc_ctrl_status_event_work(struct work_struct *work)
 
 	uvc_ctrl_status_event(w->chain, w->ctrl, w->data);
 
+	if (dev->flush_status)
+		return;
+
 	/* Resubmit the URB. */
 	w->urb->interval = dev->int_ep->desc.bInterval;
 	ret = usb_submit_urb(w->urb, GFP_KERNEL);
diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
index 7518ffce22ed..09a5802dc974 100644
--- a/drivers/media/usb/uvc/uvc_status.c
+++ b/drivers/media/usb/uvc/uvc_status.c
@@ -304,10 +304,16 @@  int uvc_status_start(struct uvc_device *dev, gfp_t flags)
 	if (dev->int_urb == NULL)
 		return 0;
 
+	dev->flush_status = false;
 	return usb_submit_urb(dev->int_urb, flags);
 }
 
 void uvc_status_stop(struct uvc_device *dev)
 {
+	struct uvc_ctrl_work *w = &dev->async_ctrl;
+
+	dev->flush_status = true;
 	usb_kill_urb(dev->int_urb);
+	if (cancel_work_sync(&w->work))
+		uvc_ctrl_status_event(w->chain, w->ctrl, w->data);
 }
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index df93db259312..6a9b72d6789e 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -560,6 +560,7 @@  struct uvc_device {
 	struct usb_host_endpoint *int_ep;
 	struct urb *int_urb;
 	u8 *status;
+	bool flush_status;
 	struct input_dev *input;
 	char input_phys[64];