[PATCH v2] media: cedrus: fix use after free bug in cedrus_remove due to race condition

[PATCH v2] media: cedrus: fix use after free bug in cedrus_remove due to race condition

[Zheng Wang]

In cedrus_probe, dev->watchdog_work is bound with cedrus_watchdog function.
In cedrus_device_run, it will started by schedule_delayed_work. If there is
an unfinished work in cedrus_remove, there may be a race condition and 
trigger UAF bug.

CPU0                  CPU1

                    |cedrus_watchdog
cedrus_remove       |
  v4l2_m2m_release  |
  kfree(m2m_dev)    |
                    |
                    | v4l2_m2m_get_curr_priv
                    |   m2m_dev //use

Fix it by canceling the worker in cedrus_remove.

Fixes: 7c38a551bda1 ("media: cedrus: Add watchdog for job completion")
Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
---
v2:
- use cancel_delayed_work_sync instead and add Fixes
label suggested by Hans Verkuil
---
 drivers/staging/media/sunxi/cedrus/cedrus.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c b/drivers/staging/media/sunxi/cedrus/cedrus.c
index a43d5ff66716..a50a4d0a8f71 100644
--- a/drivers/staging/media/sunxi/cedrus/cedrus.c
+++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
@@ -547,6 +547,7 @@ static int cedrus_remove(struct platform_device *pdev)
 {
 	struct cedrus_dev *dev = platform_get_drvdata(pdev);
 
+	cancel_delayed_work_sync(&dev->watchdog_work);
 	if (media_devnode_is_registered(dev->mdev.devnode)) {
 		media_device_unregister(&dev->mdev);
 		v4l2_m2m_unregister_media_controller(dev->m2m_dev);
-- 
2.25.1

Re: [PATCH v2] media: cedrus: fix use after free bug in cedrus_remove due to race condition

[Jernej Škrabec]

Dne ponedeljek, 13. marec 2023 ob 17:31:20 CET je Zheng Wang napisal(a):
> In cedrus_probe, dev->watchdog_work is bound with cedrus_watchdog function.
> In cedrus_device_run, it will started by schedule_delayed_work. If there is
> an unfinished work in cedrus_remove, there may be a race condition and
> trigger UAF bug.
> 
> CPU0                  CPU1
> 
>                     |cedrus_watchdog
> 
> cedrus_remove       |
>   v4l2_m2m_release  |
>   kfree(m2m_dev)    |
> 
>                     | v4l2_m2m_get_curr_priv
>                     | 
>                     |   m2m_dev //use
> 
> Fix it by canceling the worker in cedrus_remove.
> 
> Fixes: 7c38a551bda1 ("media: cedrus: Add watchdog for job completion")
> Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> ---
> v2:
> - use cancel_delayed_work_sync instead and add Fixes
> label suggested by Hans Verkuil
> ---
>  drivers/staging/media/sunxi/cedrus/cedrus.c | 1 +
>  1 file changed, 1 insertion(+)
> 

Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>

Best regards,
Jernej

> diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c
> b/drivers/staging/media/sunxi/cedrus/cedrus.c index
> a43d5ff66716..a50a4d0a8f71 100644
> --- a/drivers/staging/media/sunxi/cedrus/cedrus.c
> +++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
> @@ -547,6 +547,7 @@ static int cedrus_remove(struct platform_device *pdev)
>  {
>  	struct cedrus_dev *dev = platform_get_drvdata(pdev);
> 
> +	cancel_delayed_work_sync(&dev->watchdog_work);
>  	if (media_devnode_is_registered(dev->mdev.devnode)) {
>  		media_device_unregister(&dev->mdev);
>  		v4l2_m2m_unregister_media_controller(dev->m2m_dev);

Re: [PATCH v2] media: cedrus: fix use after free bug in cedrus_remove due to race condition

[Zheng Hacker]

Jernej Škrabec <jernej.skrabec@gmail.com> 于2023年3月15日周三 03:53写道：
>
> Dne ponedeljek, 13. marec 2023 ob 17:31:20 CET je Zheng Wang napisal(a):
> > In cedrus_probe, dev->watchdog_work is bound with cedrus_watchdog function.
> > In cedrus_device_run, it will started by schedule_delayed_work. If there is
> > an unfinished work in cedrus_remove, there may be a race condition and
> > trigger UAF bug.
> >
> > CPU0                  CPU1
> >
> >                     |cedrus_watchdog
> >
> > cedrus_remove       |
> >   v4l2_m2m_release  |
> >   kfree(m2m_dev)    |
> >
> >                     | v4l2_m2m_get_curr_priv
> >                     |
> >                     |   m2m_dev //use
> >
> > Fix it by canceling the worker in cedrus_remove.
> >
> > Fixes: 7c38a551bda1 ("media: cedrus: Add watchdog for job completion")
> > Signed-off-by: Zheng Wang <zyytlz.wz@163.com>
> > ---
> > v2:
> > - use cancel_delayed_work_sync instead and add Fixes
> > label suggested by Hans Verkuil
> > ---
> >  drivers/staging/media/sunxi/cedrus/cedrus.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
>
> Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
>

Thanks for your review.

Best regards,
Zheng

> Best regards,
> Jernej
>
> > diff --git a/drivers/staging/media/sunxi/cedrus/cedrus.c
> > b/drivers/staging/media/sunxi/cedrus/cedrus.c index
> > a43d5ff66716..a50a4d0a8f71 100644
> > --- a/drivers/staging/media/sunxi/cedrus/cedrus.c
> > +++ b/drivers/staging/media/sunxi/cedrus/cedrus.c
> > @@ -547,6 +547,7 @@ static int cedrus_remove(struct platform_device *pdev)
> >  {
> >       struct cedrus_dev *dev = platform_get_drvdata(pdev);
> >
> > +     cancel_delayed_work_sync(&dev->watchdog_work);
> >       if (media_devnode_is_registered(dev->mdev.devnode)) {
> >               media_device_unregister(&dev->mdev);
> >               v4l2_m2m_unregister_media_controller(dev->m2m_dev);
>
>
>
>