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

commit 6f6543f5 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

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;