2019-11-05 16:01:06

by Pan Bian

Subject: [PATCH] media: rockchip/rga: fix potential use after free

The variable vga->vfd is an alias for vfd. Therefore, releasing vfd and
then unregister vga->vfd will lead to a use after free bug. In fact, the
free operation and the unregister operation are reversed.

Signed-off-by: Pan Bian <[email protected]>
---
drivers/media/platform/rockchip/rga/rga.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/rockchip/rga/rga.c b/drivers/media/platform/rockchip/rga/rga.c
index e9ff12b6b5bb..613b868fce33 100644
--- a/drivers/media/platform/rockchip/rga/rga.c
+++ b/drivers/media/platform/rockchip/rga/rga.c
@@ -901,9 +901,9 @@ static int rga_probe(struct platform_device *pdev)
return 0;

rel_vdev:
- video_device_release(vfd);
-unreg_video_dev:
video_unregister_device(rga->vfd);
+unreg_video_dev:
+ video_device_release(vfd);
unreg_v4l2_dev:
v4l2_device_unregister(&rga->v4l2_dev);
err_put_clk:
--
2.7.4

2019-11-09 11:09:30

by Hans Verkuil

Subject: Re: [PATCH] media: rockchip/rga: fix potential use after free

On 11/5/19 4:55 PM, Pan Bian wrote:
> The variable vga->vfd is an alias for vfd. Therefore, releasing vfd and
> then unregister vga->vfd will lead to a use after free bug. In fact, the
> free operation and the unregister operation are reversed.
>
> Signed-off-by: Pan Bian <[email protected]>
> ---
> drivers/media/platform/rockchip/rga/rga.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/platform/rockchip/rga/rga.c b/drivers/media/platform/rockchip/rga/rga.c
> index e9ff12b6b5bb..613b868fce33 100644
> --- a/drivers/media/platform/rockchip/rga/rga.c
> +++ b/drivers/media/platform/rockchip/rga/rga.c
> @@ -901,9 +901,9 @@ static int rga_probe(struct platform_device *pdev)
> return 0;
>
> rel_vdev:
> - video_device_release(vfd);
> -unreg_video_dev:
> video_unregister_device(rga->vfd);
> +unreg_video_dev:
> + video_device_release(vfd);
> unreg_v4l2_dev:
> v4l2_device_unregister(&rga->v4l2_dev);
> err_put_clk:
>

This isn't right, you need to update the goto labels as well.

With this change unreg_video_dev releases the vdev, while rel_vdev
unregisters it. Very confusing.

I'd also rename unreg_video_dev to unreg_vdev to be consistent with
rel_vdev.

Regards,

Hans