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: [email protected]
Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives")
Reviewed-by: Yunke Cao <[email protected]>
Signed-off-by: Ricardo Ribalda <[email protected]>
---
uvc: Fix race condition on uvc
Make sure that all the async work is finished when we stop the status urb.
To: Yunke Cao <[email protected]>
To: Sergey Senozhatsky <[email protected]>
To: Max Staudt <[email protected]>
To: Laurent Pinchart <[email protected]>
To: Mauro Carvalho Chehab <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
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/[email protected]
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/[email protected]
---
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 <[email protected]>
Hi Laurent
On Wed, 14 Dec 2022 at 13:41, Laurent Pinchart
<[email protected]> 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: [email protected]
> > Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives")
> > Reviewed-by: Yunke Cao <[email protected]>
> > Signed-off-by: Ricardo Ribalda <[email protected]>
> > ---
> > uvc: Fix race condition on uvc
> >
> > Make sure that all the async work is finished when we stop the status urb.
> >
> > To: Yunke Cao <[email protected]>
> > To: Sergey Senozhatsky <[email protected]>
> > To: Max Staudt <[email protected]>
> > To: Laurent Pinchart <[email protected]>
> > To: Mauro Carvalho Chehab <[email protected]>
> > Cc: [email protected]
> > Cc: [email protected]
> > ---
> > 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/[email protected]
> >
> > 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/[email protected]
> > ---
> > 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,
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: [email protected]
> Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives")
> Reviewed-by: Yunke Cao <[email protected]>
> Signed-off-by: Ricardo Ribalda <[email protected]>
> ---
> uvc: Fix race condition on uvc
>
> Make sure that all the async work is finished when we stop the status urb.
>
> To: Yunke Cao <[email protected]>
> To: Sergey Senozhatsky <[email protected]>
> To: Max Staudt <[email protected]>
> To: Laurent Pinchart <[email protected]>
> To: Mauro Carvalho Chehab <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> ---
> 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/[email protected]
>
> 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/[email protected]
> ---
> 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 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: [email protected]
> > > Fixes: e5225c820c05 ("media: uvcvideo: Send a control event when a Control Change interrupt arrives")
> > > Reviewed-by: Yunke Cao <[email protected]>
> > > Signed-off-by: Ricardo Ribalda <[email protected]>
> > > ---
> > > uvc: Fix race condition on uvc
> > >
> > > Make sure that all the async work is finished when we stop the status urb.
> > >
> > > To: Yunke Cao <[email protected]>
> > > To: Sergey Senozhatsky <[email protected]>
> > > To: Max Staudt <[email protected]>
> > > To: Laurent Pinchart <[email protected]>
> > > To: Mauro Carvalho Chehab <[email protected]>
> > > Cc: [email protected]
> > > Cc: [email protected]
> > > ---
> > > 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/[email protected]
> > >
> > > 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/[email protected]
> > > ---
> > > 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
<[email protected]> 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