Re: [PATCH 1/6] media: v4l2-dev: Add range check for vdev->minor

[Sakari Ailus]

Hi Ricardo,

On Tue, Apr 28, 2026 at 12:41:07PM +0000, Ricardo Ribalda wrote:
> If the fixed minor ranges are not properly set we could end up in a
> situation where the calculated minor is invalid. Add a check for this in
> the code.
> 
> This check also fixes the following smatch warning:
> 
> drivers/media/v4l2-core/v4l2-dev.c:1036 __video_register_device() error: buffer overflow 'video_devices' 256 <= 288
> drivers/media/v4l2-core/v4l2-dev.c:1043 __video_register_device() error: buffer overflow 'video_devices' 256 <= 288
> drivers/media/v4l2-core/v4l2-dev.c:1101 __video_register_device() error: buffer overflow 'video_devices' 256 <= 288
> 
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> ---
>  drivers/media/v4l2-core/v4l2-dev.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> index 6ce623a1245a..a731ffdb91ee 100644
> --- a/drivers/media/v4l2-core/v4l2-dev.c
> +++ b/drivers/media/v4l2-core/v4l2-dev.c
> @@ -1032,6 +1032,12 @@ int __video_register_device(struct video_device *vdev,
>  	vdev->minor = i + minor_offset;
>  	vdev->num = nr;
>  
> +	if (WARN_ON(vdev->minor >= VIDEO_NUM_DEVICES)) {

Could this be combined with the should-not-happen case below? The error
handling is the same (releasing the mutex) and the error code could be as
well. I think the message can be just as well removed as we have a
WARN_ON() here anyway.

I wonder what Hans thinks.

> +		mutex_unlock(&videodev_lock);
> +		pr_err("invalid minor. Check ranges.\n");
> +		return -EINVAL;
> +	}
> +
>  	/* Should not happen since we thought this minor was free */
>  	if (WARN_ON(video_devices[vdev->minor])) {
>  		mutex_unlock(&videodev_lock);
> 

-- 
Kind regards,

Sakari Ailus