usb: core: add sanity checks when using bInterfaceClass with new_id

Check if that field is actually used and if so, bail out if it exeeds a
u8. Make it also future-proof by not requiring "exactly three"
parameters in new_id, but simply "more than two".

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/driver.c

@@ -60,7 +60,10 @@ ssize_t usb_store_new_id(struct usb_dynids *dynids,
 	dynid->id.idVendor = idVendor;
 	dynid->id.idProduct = idProduct;
 	dynid->id.match_flags = USB_DEVICE_ID_MATCH_DEVICE;
-	if (fields == 3) {
+	if (fields > 2 && bInterfaceClass) {
+		if (bInterfaceClass > 255)
+			return -EINVAL;
+
 		dynid->id.bInterfaceClass = (u8)bInterfaceClass;
 		dynid->id.match_flags |= USB_DEVICE_ID_MATCH_INT_CLASS;
 	}