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(+)
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);
+ 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
Best regards,
--
Ricardo Ribalda <ribalda@chromium.org>
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
Hi Laurent On Wed, 14 Dec 2022 at 13:41, Laurent Pinchart <laurent.pinchart@ideasonboard.com> wrote: > > 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 ? Indeed... I could add a mutex just for flush_status what do you think? > > 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 -- Ricardo Ribalda
Hi Ricardo, On Wed, Dec 14, 2022 at 01:44:56PM +0100, Ricardo Ribalda wrote: > On Wed, 14 Dec 2022 at 13:41, Laurent Pinchart wrote: > > 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 ? > > Indeed... > > I could add a mutex just for flush_status > > what do you think? It may be possible to avoid that. I'm giving it a try. > > > > 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
Hi Laurent On Wed, 14 Dec 2022 at 14:30, Laurent Pinchart <laurent.pinchart@ideasonboard.com> wrote: > > > Isn't this still racy ? > > > > Indeed... > > > > I could add a mutex just for flush_status > > > > what do you think? > > It may be possible to avoid that. I'm giving it a try. Just sent a new version without lock... -- Ricardo Ribalda
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