Messages in this thread Patch in this message |  | | Date | Wed, 14 Dec 2022 14:41:36 +0200 | From | Laurent Pinchart <> | Subject | Re: [PATCH v3] media: uvcvideo: Fix race condition with usb_kill_urb |
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Hi Ricardo,
Thank you for the patch.
On Wed, Dec 14, 2022 at 12:18:52PM +0100, Ricardo Ribalda 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") > Reviewed-by: Yunke Cao <yunkec@chromium.org> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org> > --- > uvc: Fix race condition on uvc > > Make sure that all the async work is finished when we stop the status urb. > > To: Yunke Cao <yunkec@chromium.org> > To: Sergey Senozhatsky <senozhatsky@chromium.org> > To: Max Staudt <mstaudt@google.com> > To: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > To: Mauro Carvalho Chehab <mchehab@kernel.org> > Cc: linux-media@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > --- > Changes in v3: > - Remove the patch for dev->status, makes more sense in another series, and makes > the zero day less nervous. > - Update reviewed-by (thanks Yunke!). > - Link to v2: https://lore.kernel.org/r/20221212-uvc-race-v2-0-54496cc3b8ab@chromium.org > > Changes in v2: > - Add a patch for not kalloc dev->status > - Redo the logic mechanism, so it also works with suspend (Thanks Yunke!) > - Link to v1: https://lore.kernel.org/r/20221212-uvc-race-v1-0-c52e1783c31d@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);
Isn't this still racy ?
CPU0 CPU1 ==== ====
uvc_status_stop() uvc_ctrl_status_event_work() { { if (dev->flush_status) return;
dev->flush_status = true; usb_kill_urb(dev->int_urb);
/* Resubmit the URB. */ w->urb->interval = dev->int_ep->desc.bInterval; ret = usb_submit_urb(w->urb, GFP_KERNEL); }
if (cancel_work_sync(&w->work)) uvc_ctrl_status_event(w->chain, w->ctrl, w->data); }
uvc_status_start() will then return an error, right ?
> + 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]; > > > --- > base-commit: 0ec5a38bf8499f403f81cb81a0e3a60887d1993c > change-id: 20221212-uvc-race-09276ea68bf8
-- Regards,
Laurent Pinchart
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