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SubjectRe: [PATCH v2] media: rockchip/rga: fix potential use after free
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On 11/11/19 9:28 AM, 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>
> ---
> v2: update the goto label names consistently
> ---
> drivers/media/platform/rockchip/rga/rga.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/platform/rockchip/rga/rga.c b/drivers/media/platform/rockchip/rga/rga.c
> index e9ff12b6b5bb..d2297abafc69 100644
> --- a/drivers/media/platform/rockchip/rga/rga.c
> +++ b/drivers/media/platform/rockchip/rga/rga.c
> @@ -863,7 +863,7 @@ static int rga_probe(struct platform_device *pdev)
> if (IS_ERR(rga->m2m_dev)) {
> v4l2_err(&rga->v4l2_dev, "Failed to init mem2mem device\n");
> ret = PTR_ERR(rga->m2m_dev);
> - goto unreg_video_dev;
> + goto rel_vdev;
> }
>
> pm_runtime_get_sync(rga->dev);
> @@ -892,7 +892,7 @@ static int rga_probe(struct platform_device *pdev)
> ret = video_register_device(vfd, VFL_TYPE_GRABBER, -1);
> if (ret) {
> v4l2_err(&rga->v4l2_dev, "Failed to register video device\n");
> - goto rel_vdev;
> + goto unreg_dev;
> }
>
> v4l2_info(&rga->v4l2_dev, "Registered %s as /dev/%s\n",
> @@ -900,10 +900,10 @@ static int rga_probe(struct platform_device *pdev)
>
> return 0;
>
> +unreg_dev:
> + video_unregister_device(rga->vfd);

This is wrong. If video_register_device fails, then you call video_device_release,
not video_unregister_device. The unreg_video_dev case is bogus and should be removed.

Instead you need a v4l2_m2m_release() call to clean up the v4l2_m2m_init() result
if there is an error.

Regards,

Hans

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

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