linux-kernel - Re: [PATCH v1 1/1] media: uvc: Handle cameras with invalid descriptors

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Message-ID: <Yypgi6Jc9/tZLtIw@pendragon.ideasonboard.com>
Date:   Wed, 21 Sep 2022 03:53:31 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Ricardo Ribalda <ribalda@...omium.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot <syzkaller@...glegroups.com>
Subject: Re: [PATCH v1 1/1] media: uvc: Handle cameras with invalid
 descriptors

Hi Ricardo,

Thank you for the patch.

On Tue, Sep 20, 2022 at 04:04:55PM +0200, Ricardo Ribalda wrote:
> If the source entity does not contain any pads, do not create a link.
> 
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> 
> diff --git a/drivers/media/usb/uvc/uvc_entity.c b/drivers/media/usb/uvc/uvc_entity.c
> index 7c4d2f93d351..1f730cb72e58 100644
> --- a/drivers/media/usb/uvc/uvc_entity.c
> +++ b/drivers/media/usb/uvc/uvc_entity.c
> @@ -43,7 +43,7 @@ static int uvc_mc_create_links(struct uvc_video_chain *chain,
>  		source = (UVC_ENTITY_TYPE(remote) == UVC_TT_STREAMING)
>  		       ? (remote->vdev ? &remote->vdev->entity : NULL)
>  		       : &remote->subdev.entity;
> -		if (source == NULL)
> +		if (source == NULL || source->num_pads == 0)

source->num_pads and remote->num_pads should always be identical, but as
the next line uses remote->num_pads, wouldn't it be better to test that
variable ? If so, I'd move the test a file lines earlier, with the
remote == NULL test.

What do you think ? If you agree I can make that change when applying,
there's no need for a new version. Otherwise I'll keep the patch as-is.

>  			continue;
>  
>  		remote_pad = remote->num_pads - 1;
> 

-- 
Regards,

Laurent Pinchart