linux-kernel - Re: [PATCH Next] media: mc: Clear minor number before put device

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Message-ID: <20250910092233.GA20904@pendragon.ideasonboard.com>
Date: Wed, 10 Sep 2025 12:22:33 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Edward Adam Davis <eadavis@...com>
Cc: syzbot+031d0cfd7c362817963f@...kaller.appspotmail.com,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	mchehab@...nel.org, sakari.ailus@...ux.intel.com,
	syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH Next] media: mc: Clear minor number before put device

Hello Edward,

On Wed, Sep 10, 2025 at 09:15:27AM +0800, Edward Adam Davis wrote:
> The device minor should not be cleared after the device is released.

The most important piece of information in a commit message is the
reason for the patch. You need to explain *why* this is needed, not just
state it should be done.

> Fixes: 9e14868dc952 ("media: mc: Clear minor number reservation at unregistration time")
> Reported-by: syzbot+031d0cfd7c362817963f@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=031d0cfd7c362817963f
> Tested-by: syzbot+031d0cfd7c362817963f@...kaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@...com>
> ---
>  drivers/media/mc/mc-devnode.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/media/mc/mc-devnode.c b/drivers/media/mc/mc-devnode.c
> index 0d01cbae98f2..6daa7aa99442 100644
> --- a/drivers/media/mc/mc-devnode.c
> +++ b/drivers/media/mc/mc-devnode.c
> @@ -276,13 +276,10 @@ void media_devnode_unregister(struct media_devnode *devnode)
>  	/* Delete the cdev on this minor as well */
>  	cdev_device_del(&devnode->cdev, &devnode->dev);
>  	devnode->media_dev = NULL;
> +	clear_bit(devnode->minor, media_devnode_nums);
>  	mutex_unlock(&media_devnode_lock);
>  
>  	put_device(&devnode->dev);
> -
> -	mutex_lock(&media_devnode_lock);
> -	clear_bit(devnode->minor, media_devnode_nums);
> -	mutex_unlock(&media_devnode_lock);
>  }
>  
>  /*

-- 
Regards,

Laurent Pinchart