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

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

[Pan Bian]

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 <bianpan2016@163.com>
---
 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


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

[Hans Verkuil]

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 <bianpan2016@163.com>
> ---
>  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

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