usb gadget: uvc: uvc_request_data::length field must be signed

The field is used to pass the UVC request data length, but can also be
used to signal an error when setting it to a negative value. Switch from
unsigned int to __s32.

Reported-by: Fernandez Gonzalo <gfernandez@copreci.es>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/uvc.h

@@ -28,7 +28,7 @@
 
 struct uvc_request_data
 {
-	unsigned int length;
+	__s32 length;
 	__u8 data[60];
 };
 

drivers/usb/gadget/uvc_v4l2.c

@@ -39,7 +39,7 @@ uvc_send_response(struct uvc_device *uvc, struct uvc_request_data *data)
 	if (data->length < 0)
 		return usb_ep_set_halt(cdev->gadget->ep0);
 
-	req->length = min(uvc->event_length, data->length);
+	req->length = min_t(unsigned int, uvc->event_length, data->length);
 	req->zero = data->length < uvc->event_length;
 	req->dma = DMA_ADDR_INVALID;