linux-kernel - Re: [PATCH] Prevent buffer overflow in UVC Gadget setup handler

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Message-ID: <780379d9-2331-cd7a-126d-cdaa8aec023d@ideasonboard.com>
Date:   Thu, 1 Dec 2022 13:49:38 +0000
From:   Dan Scally <dan.scally@...asonboard.com>
To:     Szymon Heidrich <szymon.heidrich@...il.com>,
        laurent.pinchart@...asonboard.com
Cc:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Prevent buffer overflow in UVC Gadget setup handler

Hello - thanks for the patch

On 01/12/2022 12:21, Szymon Heidrich wrote:
> Setup function uvc_function_setup


You've written uvc_function_setup here, but the code changes 
uvc_function_ep0_complete.

>   permits control transfer
> requests with up to 64 bytes of payload (UVC_MAX_REQUEST_SIZE),
> data stage handler for OUT transfer uses memcpy to copy req->actual
> bytes to uvc_event->data.data array of size 60. This may result
> in an overflow of 4 bytes.
>
> Signed-off-by: Szymon Heidrich <szymon.heidrich@...il.com>


Good catch

> ---
>   drivers/usb/gadget/function/f_uvc.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/usb/gadget/function/f_uvc.c b/drivers/usb/gadget/function/f_uvc.c
> index 6e196e061..69c5eb3a3 100644
> --- a/drivers/usb/gadget/function/f_uvc.c
> +++ b/drivers/usb/gadget/function/f_uvc.c
> @@ -216,8 +216,9 @@ uvc_function_ep0_complete(struct usb_ep *ep, struct usb_request *req)
>   
>   		memset(&v4l2_event, 0, sizeof(v4l2_event));
>   		v4l2_event.type = UVC_EVENT_DATA;
> -		uvc_event->data.length = req->actual;
> -		memcpy(&uvc_event->data.data, req->buf, req->actual);
> +		uvc_event->data.length = (req->actual > sizeof(uvc_event->data.data) ?
> +			sizeof(uvc_event->data.data) : req->actual);


There's a clamp() macro in f_uvc.c, can we use that?

> +		memcpy(&uvc_event->data.data, req->buf, uvc_event->data.length);
>   		v4l2_event_queue(&uvc->vdev, &v4l2_event);
>   	}
>   }