USB: cdc-acm: check for valid interfaces

We need to check that we have both a valid data and control inteface for both
types of headers (union and not union.)

References: https://bugzilla.kernel.org/show_bug.cgi?id=83551
Reported-by: Simon Schubert <2+kernel@0x2c.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/class/cdc-acm.c

@@ -1195,10 +1195,11 @@ next_desc:
 	} else {
 		control_interface = usb_ifnum_to_if(usb_dev, union_header->bMasterInterface0);
 		data_interface = usb_ifnum_to_if(usb_dev, (data_interface_num = union_header->bSlaveInterface0));
-		if (!control_interface || !data_interface) {
-			dev_dbg(&intf->dev, "no interfaces\n");
-			return -ENODEV;
-		}
+	}
+
+	if (!control_interface || !data_interface) {
+		dev_dbg(&intf->dev, "no interfaces\n");
+		return -ENODEV;
 	}
 
 	if (data_interface_num != call_interface_num)