Re: [PATCH] media: uvcvideo: Fix bounds for descriptor parsing

[Laurent Pinchart]

Hi Ricardo,

Thank you for the patch.

On Fri, Sep 11, 2026 at 01:23:50PM +0000, Ricardo Ribalda wrote:
> uvc_parse_control() passes descriptor by descriptor to
> uvc_parse_standard_control() with the number of bytes remaining in the
> buffer, not the number of bytes of that descriptor.
> 
> Because of this, malformed descriptors could leak over the next
> descriptor, leaving malformed data in our structures.

What issue does this fix in practice ?

> Change the code so we pass the actual length of the descriptor to the
> parser.
> 
> Note that this makes the existing check more strict and some devices
> that are wrongly parsed today will not be probed now.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index e289cc71ba98..429f1ab19a2a 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -1248,11 +1248,14 @@ static int uvc_parse_control(struct uvc_device *dev)
>  	 */
>  
>  	while (buflen > 2) {
> -		if (uvc_parse_vendor_control(dev, buffer, buflen) ||
> +		if (buflen < buffer[0] || buffer[0] < 3)
> +			return -EINVAL;
> +
> +		if (uvc_parse_vendor_control(dev, buffer, buffer[0]) ||
>  		    buffer[1] != USB_DT_CS_INTERFACE)
>  			goto next_descriptor;
>  
> -		ret = uvc_parse_standard_control(dev, buffer, buflen);
> +		ret = uvc_parse_standard_control(dev, buffer, buffer[0]);
>  		if (ret < 0)
>  			return ret;
>  
> 
> ---
> base-commit: 27953c044974baf7e24dee3e9342fe0103dea80c
> change-id: 20260911-uvc-ctrl-bound-9c1940f06fc7

-- 
Regards,

Laurent Pinchart