[v3] media:exynos4-is: Fix a use after free in isp_video_release

Message ID 20210427132734.5212-1-lyl2019@mail.ustc.edu.cn
State New
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  • [v3] media:exynos4-is: Fix a use after free in isp_video_release
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Commit Message

Lv Yunlong April 27, 2021, 1:27 p.m.
In isp_video_release, file->private_data is freed via
_vb2_fop_release()->v4l2_fh_release(). But the freed
file->private_data is still used in v4l2_fh_is_singular_file()
->v4l2_fh_is_singular(file->private_data), which is a use
after free bug.

My patch sets file->private_data to NULL after _vb2_fop_release()
to avoid the use after free, and uses a variable 'is_singular_file'
to keep the original function unchanged.

Fixes: 34947b8aebe3f ("[media] exynos4-is: Add the FIMC-IS ISP capture DMA driver")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
---
 drivers/media/platform/exynos4-is/fimc-isp-video.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Comments

Hans Verkuil May 5, 2021, 9:31 a.m. | #1
Hi Lv Yunlong,

On 27/04/2021 15:27, Lv Yunlong wrote:
> In isp_video_release, file->private_data is freed via
> _vb2_fop_release()->v4l2_fh_release(). But the freed
> file->private_data is still used in v4l2_fh_is_singular_file()
> ->v4l2_fh_is_singular(file->private_data), which is a use
> after free bug.
> 
> My patch sets file->private_data to NULL after _vb2_fop_release()
> to avoid the use after free, and uses a variable 'is_singular_file'
> to keep the original function unchanged.

Actually, it is the use of 'is_singular_file' that fixes the bug,
the 'file->private_data = NULL;' is unnecessary here.

That said, it would be a really good idea if in a separate patch you
make v4l2_fh_release() more robust by setting filp->private_data to
NULL after the kfree(fh).

Regards,

	Hans

> 
> Fixes: 34947b8aebe3f ("[media] exynos4-is: Add the FIMC-IS ISP capture DMA driver")
> Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
> ---
>  drivers/media/platform/exynos4-is/fimc-isp-video.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/exynos4-is/fimc-isp-video.c b/drivers/media/platform/exynos4-is/fimc-isp-video.c
> index 612b9872afc8..c07dcb0bccc2 100644
> --- a/drivers/media/platform/exynos4-is/fimc-isp-video.c
> +++ b/drivers/media/platform/exynos4-is/fimc-isp-video.c
> @@ -306,17 +306,21 @@ static int isp_video_release(struct file *file)
>  	struct fimc_is_video *ivc = &isp->video_capture;
>  	struct media_entity *entity = &ivc->ve.vdev.entity;
>  	struct media_device *mdev = entity->graph_obj.mdev;
> +	bool is_singular_file;
>  
>  	mutex_lock(&isp->video_lock);
>  
> -	if (v4l2_fh_is_singular_file(file) && ivc->streaming) {
> +	is_singular_file = v4l2_fh_is_singular_file(file);
> +
> +	if (is_singular_file && ivc->streaming) {
>  		media_pipeline_stop(entity);
>  		ivc->streaming = 0;
>  	}
>  
>  	_vb2_fop_release(file, NULL);
> +	file->private_data = NULL;
>  
> -	if (v4l2_fh_is_singular_file(file)) {
> +	if (is_singular_file) {
>  		fimc_pipeline_call(&ivc->ve, close);
>  
>  		mutex_lock(&mdev->graph_mutex);
>
Lv Yunlong May 6, 2021, 7:19 a.m. | #2
> -----原始邮件-----

> 发件人: "Hans Verkuil" <hverkuil@xs4all.nl>

> 发送时间: 2021-05-05 17:31:04 (星期三)

> 收件人: "Lv Yunlong" <lyl2019@mail.ustc.edu.cn>, s.nawrocki@samsung.com, mchehab@kernel.org, krzk@kernel.org

> 抄送: linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org

> 主题: Re: [PATCH v3] media:exynos4-is: Fix a use after free in isp_video_release

> 

> Hi Lv Yunlong,

> 

> On 27/04/2021 15:27, Lv Yunlong wrote:

> > In isp_video_release, file->private_data is freed via

> > _vb2_fop_release()->v4l2_fh_release(). But the freed

> > file->private_data is still used in v4l2_fh_is_singular_file()

> > ->v4l2_fh_is_singular(file->private_data), which is a use

> > after free bug.

> > 

> > My patch sets file->private_data to NULL after _vb2_fop_release()

> > to avoid the use after free, and uses a variable 'is_singular_file'

> > to keep the original function unchanged.

> 

> Actually, it is the use of 'is_singular_file' that fixes the bug,

> the 'file->private_data = NULL;' is unnecessary here.

> 

> That said, it would be a really good idea if in a separate patch you

> make v4l2_fh_release() more robust by setting filp->private_data to

> NULL after the kfree(fh).

> 

> Regards,

> 

> 	Hans

> 

> > 

> > Fixes: 34947b8aebe3f ("[media] exynos4-is: Add the FIMC-IS ISP capture DMA driver")

> > Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>

> > ---

> >  drivers/media/platform/exynos4-is/fimc-isp-video.c | 8 ++++++--

> >  1 file changed, 6 insertions(+), 2 deletions(-)

> > 

> > diff --git a/drivers/media/platform/exynos4-is/fimc-isp-video.c b/drivers/media/platform/exynos4-is/fimc-isp-video.c

> > index 612b9872afc8..c07dcb0bccc2 100644

> > --- a/drivers/media/platform/exynos4-is/fimc-isp-video.c

> > +++ b/drivers/media/platform/exynos4-is/fimc-isp-video.c

> > @@ -306,17 +306,21 @@ static int isp_video_release(struct file *file)

> >  	struct fimc_is_video *ivc = &isp->video_capture;

> >  	struct media_entity *entity = &ivc->ve.vdev.entity;

> >  	struct media_device *mdev = entity->graph_obj.mdev;

> > +	bool is_singular_file;

> >  

> >  	mutex_lock(&isp->video_lock);

> >  

> > -	if (v4l2_fh_is_singular_file(file) && ivc->streaming) {

> > +	is_singular_file = v4l2_fh_is_singular_file(file);

> > +

> > +	if (is_singular_file && ivc->streaming) {

> >  		media_pipeline_stop(entity);

> >  		ivc->streaming = 0;

> >  	}

> >  

> >  	_vb2_fop_release(file, NULL);

> > +	file->private_data = NULL;

> >  

> > -	if (v4l2_fh_is_singular_file(file)) {

> > +	if (is_singular_file) {

> >  		fimc_pipeline_call(&ivc->ve, close);

> >  

> >  		mutex_lock(&mdev->graph_mutex);

> > 

> 



Ok, thanks for your suggestion.

Do you means i need submit a new path to set filp->private_data = NULL
after kfree(fh) in v4l2_fh_release() ?

Lv Yunlong
Hans Verkuil May 6, 2021, 7:23 a.m. | #3
On 06/05/2021 09:19, lyl2019@mail.ustc.edu.cn wrote:
> 

> 

> 

>> -----原始邮件-----

>> 发件人: "Hans Verkuil" <hverkuil@xs4all.nl>

>> 发送时间: 2021-05-05 17:31:04 (星期三)

>> 收件人: "Lv Yunlong" <lyl2019@mail.ustc.edu.cn>, s.nawrocki@samsung.com, mchehab@kernel.org, krzk@kernel.org

>> 抄送: linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org

>> 主题: Re: [PATCH v3] media:exynos4-is: Fix a use after free in isp_video_release

>>

>> Hi Lv Yunlong,

>>

>> On 27/04/2021 15:27, Lv Yunlong wrote:

>>> In isp_video_release, file->private_data is freed via

>>> _vb2_fop_release()->v4l2_fh_release(). But the freed

>>> file->private_data is still used in v4l2_fh_is_singular_file()

>>> ->v4l2_fh_is_singular(file->private_data), which is a use

>>> after free bug.

>>>

>>> My patch sets file->private_data to NULL after _vb2_fop_release()

>>> to avoid the use after free, and uses a variable 'is_singular_file'

>>> to keep the original function unchanged.

>>

>> Actually, it is the use of 'is_singular_file' that fixes the bug,

>> the 'file->private_data = NULL;' is unnecessary here.

>>

>> That said, it would be a really good idea if in a separate patch you

>> make v4l2_fh_release() more robust by setting filp->private_data to

>> NULL after the kfree(fh).

>>

>> Regards,

>>

>> 	Hans

>>

>>>

>>> Fixes: 34947b8aebe3f ("[media] exynos4-is: Add the FIMC-IS ISP capture DMA driver")

>>> Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>

>>> ---

>>>  drivers/media/platform/exynos4-is/fimc-isp-video.c | 8 ++++++--

>>>  1 file changed, 6 insertions(+), 2 deletions(-)

>>>

>>> diff --git a/drivers/media/platform/exynos4-is/fimc-isp-video.c b/drivers/media/platform/exynos4-is/fimc-isp-video.c

>>> index 612b9872afc8..c07dcb0bccc2 100644

>>> --- a/drivers/media/platform/exynos4-is/fimc-isp-video.c

>>> +++ b/drivers/media/platform/exynos4-is/fimc-isp-video.c

>>> @@ -306,17 +306,21 @@ static int isp_video_release(struct file *file)

>>>  	struct fimc_is_video *ivc = &isp->video_capture;

>>>  	struct media_entity *entity = &ivc->ve.vdev.entity;

>>>  	struct media_device *mdev = entity->graph_obj.mdev;

>>> +	bool is_singular_file;

>>>  

>>>  	mutex_lock(&isp->video_lock);

>>>  

>>> -	if (v4l2_fh_is_singular_file(file) && ivc->streaming) {

>>> +	is_singular_file = v4l2_fh_is_singular_file(file);

>>> +

>>> +	if (is_singular_file && ivc->streaming) {

>>>  		media_pipeline_stop(entity);

>>>  		ivc->streaming = 0;

>>>  	}

>>>  

>>>  	_vb2_fop_release(file, NULL);

>>> +	file->private_data = NULL;

>>>  

>>> -	if (v4l2_fh_is_singular_file(file)) {

>>> +	if (is_singular_file) {

>>>  		fimc_pipeline_call(&ivc->ve, close);

>>>  

>>>  		mutex_lock(&mdev->graph_mutex);

>>>

>>

> 

> 

> Ok, thanks for your suggestion.

> 

> Do you means i need submit a new path to set filp->private_data = NULL

> after kfree(fh) in v4l2_fh_release() ?


Yes, so one updated patch for fimc-isp-video.c and a second patch for v4l2-fh.c.

Regards,

	Hans

> 

> Lv Yunlong

>

Patch

diff --git a/drivers/media/platform/exynos4-is/fimc-isp-video.c b/drivers/media/platform/exynos4-is/fimc-isp-video.c
index 612b9872afc8..c07dcb0bccc2 100644
--- a/drivers/media/platform/exynos4-is/fimc-isp-video.c
+++ b/drivers/media/platform/exynos4-is/fimc-isp-video.c
@@ -306,17 +306,21 @@  static int isp_video_release(struct file *file)
 	struct fimc_is_video *ivc = &isp->video_capture;
 	struct media_entity *entity = &ivc->ve.vdev.entity;
 	struct media_device *mdev = entity->graph_obj.mdev;
+	bool is_singular_file;
 
 	mutex_lock(&isp->video_lock);
 
-	if (v4l2_fh_is_singular_file(file) && ivc->streaming) {
+	is_singular_file = v4l2_fh_is_singular_file(file);
+
+	if (is_singular_file && ivc->streaming) {
 		media_pipeline_stop(entity);
 		ivc->streaming = 0;
 	}
 
 	_vb2_fop_release(file, NULL);
+	file->private_data = NULL;
 
-	if (v4l2_fh_is_singular_file(file)) {
+	if (is_singular_file) {
 		fimc_pipeline_call(&ivc->ve, close);
 
 		mutex_lock(&mdev->graph_mutex);