[PATCH] media: s5p-g2d: avoid double free on video register failure

[Lukasz Stelmach]

It was 2026-05-17 nie 19:46, when Guangshuo Li wrote:
> g2d_probe() allocates a video_device with video_device_alloc() and
> releases it from the rel_vdev error path if video_register_device()
> fails.
>
> This can double free the video_device when __video_register_device()
> reaches device_register() and that call fails:
>
>   video_register_device()
>     -> __video_register_device()
>        -> device_register() fails
>           -> put_device(&vdev->dev)
>              -> v4l2_device_release()
>                 -> vdev->release(vdev)
>                    -> video_device_release(vdev)
>
>   g2d_probe()
>     -> rel_vdev
>        -> video_device_release(vfd)
>
> Use video_device_release_empty() while registering the device so that
> registration failure paths do not free vfd through vdev->release().
> g2d_probe() then releases vfd exactly once from rel_vdev. Restore
> video_device_release() after successful registration so the registered
> device keeps its normal lifetime handling.
>
> This issue was found by a static analysis tool I am developing.

Thank you for taking time to analyze our code. I was going to write
something along the lines Marek Szyprowski has laready written in this
thread https://lore.kernel.org/all/CANUHTR-RfWnoMRRAoDb6CPZsaiAYBLy61dd0P6TnKYgjNeBWpA@mail.gmail.com/
Do follow his advise with this one too.

> Fixes: 918847341af0 ("[media] v4l: add G2D driver for s5p device family")
> Signed-off-by: Guangshuo Li <lgs201920130244 at gmail.com>
> ---
>  drivers/media/platform/samsung/s5p-g2d/g2d.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/media/platform/samsung/s5p-g2d/g2d.c b/drivers/media/platform/samsung/s5p-g2d/g2d.c
> index a18b13db19d5..f38c28abd6d9 100644
> --- a/drivers/media/platform/samsung/s5p-g2d/g2d.c
> +++ b/drivers/media/platform/samsung/s5p-g2d/g2d.c
> @@ -684,6 +684,7 @@ static int g2d_probe(struct platform_device *pdev)
>  		goto unreg_v4l2_dev;
>  	}
>  	*vfd = g2d_videodev;
> +	vfd->release = video_device_release_empty;
>  	set_bit(V4L2_FL_QUIRK_INVERTED_CROP, &vfd->flags);
>  	vfd->lock = &dev->mutex;
>  	vfd->v4l2_dev = &dev->v4l2_dev;
> @@ -711,6 +712,8 @@ static int g2d_probe(struct platform_device *pdev)
>  		v4l2_err(&dev->v4l2_dev, "Failed to register video device\n");
>  		goto free_m2m;
>  	}
> +
> +	vfd->release = video_device_release;
>  	video_set_drvdata(vfd, dev);
>  	dev->vfd = vfd;
>  	v4l2_info(&dev->v4l2_dev, "device registered as /dev/video%d\n",

-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics
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