diff --git a/drivers/usb/serial/io_ti.c b/drivers/usb/serial/io_ti.c
index 0fc2da9..a417756 100644
--- a/drivers/usb/serial/io_ti.c
+++ b/drivers/usb/serial/io_ti.c
@@ -1681,6 +1681,12 @@
 	function    = TIUMP_GET_FUNC_FROM_CODE(data[0]);
 	dbg("%s - port_number %d, function %d, info 0x%x",
 	     __func__, port_number, function, data[1]);
+
+	if (port_number >= edge_serial->serial->num_ports) {
+		dev_err(&urb->dev->dev, "bad port number %d\n", port_number);
+		goto exit;
+	}
+
 	port = edge_serial->serial->port[port_number];
 	edge_port = usb_get_serial_port_data(port);
 	if (!edge_port) {