linux-kernel - Re: [PATCH] media: uvc_video: fix bit overflow in uvc_probe

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Message-ID: <Yjx3laKM9Ah+1PRC@pendragon.ideasonboard.com>
Date:   Thu, 24 Mar 2022 15:52:21 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Hangyu Hua <hbh25y@...il.com>
Cc:     mchehab@...nel.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: uvc_video: fix bit overflow in uvc_probe_video

Hi Hangyu,

Thank you for the patch.

On Thu, Mar 24, 2022 at 05:13:08PM +0800, Hangyu Hua wrote:
> probe->dwMaxPayloadTransferSize is a 32bit value, but bandwidth is 16bit. This
> may lead to a bit overflow.
> 
> Signed-off-by: Hangyu Hua <hbh25y@...il.com>
> ---
>  drivers/media/usb/uvc/uvc_video.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index 1b4cc934109e..cc4878373aa7 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -383,7 +383,7 @@ int uvc_probe_video(struct uvc_streaming *stream,
>  	struct uvc_streaming_control *probe)
>  {
>  	struct uvc_streaming_control probe_min, probe_max;
> -	u16 bandwidth;
> +	u32 bandwidth;
>  	unsigned int i;
>  	int ret;
>  
> @@ -422,7 +422,7 @@ int uvc_probe_video(struct uvc_streaming *stream,
>  			break;
>  
>  		bandwidth = probe->dwMaxPayloadTransferSize;
> -		if (bandwidth <= stream->maxpsize)
> +		if (bandwidth <= (u32)stream->maxpsize)

The cast to u32 isn't needed, it's implicit.

This could actually be written

	if (probe->dwMaxPayloadTransferSize <= stream->maxpsize)

The bandwidth local variable can be dropped. Could you submit a v2 with
this change ?

>  			break;
>  
>  		if (stream->dev->quirks & UVC_QUIRK_PROBE_MINMAX) {

-- 
Regards,

Laurent Pinchart