2023-03-13 16:34:12

by Zheng Wang

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

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 <[email protected]>
---
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

2023-03-14 19:53:46

by Jernej Škrabec

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

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 <[email protected]>
> ---
> 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 <[email protected]>

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);

2023-03-15 09:00:15

by Zheng Hacker

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

Jernej Škrabec <[email protected]> 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 <[email protected]>
> > ---
> > 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 <[email protected]>
>

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);
>
>
>
>