linux-kernel - Re: [PATCH v3] usb: gadget: uvc: Prevent buffer overflow in setup handler

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Date:   Tue, 6 Dec 2022 22:43:18 +0100
From:   Szymon Heidrich <szymon.heidrich@...il.com>
To:     dan.scally@...asonboard.com,
        Laurent Pinchart <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 v3] usb: gadget: uvc: Prevent buffer overflow in setup
 handler

On 06/12/2022 22:21, Laurent Pinchart wrote:
> Hi Szymon,
> 
> Thank you for the patch.
> 
> On Tue, Dec 06, 2022 at 03:13:01PM +0100, Szymon Heidrich wrote:
>> Setup function uvc_function_setup 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.
>>
>> Fixes: cdda479f15cd ("USB gadget: video class function driver")
>> Signed-off-by: Szymon Heidrich <szymon.heidrich@...il.com>
> 
> Good catch.
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> 
>> ---
>> V1 -> V2: Corrected commit message and changed ?: in favor of min_t
>> V2 -> V3: Added fixes tag
>>
>>  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..4419b7972 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 = min_t(unsigned int, req->actual,
>> +			sizeof(uvc_event->data.data));
>> +		memcpy(&uvc_event->data.data, req->buf, uvc_event->data.length);
>>  		v4l2_event_queue(&uvc->vdev, &v4l2_event);
>>  	}
>>  }
> 

Hello Dan and Laurent,

Thank you very much for your time, review and accurate remarks.

Best regards,
Szymon