diff --git a/drivers/usb/serial/whiteheat.c b/drivers/usb/serial/whiteheat.c
index d3ea90bef84d..52b4f8ad93d0 100644
--- a/drivers/usb/serial/whiteheat.c
+++ b/drivers/usb/serial/whiteheat.c
@@ -604,6 +604,10 @@ static int firm_send_command(struct usb_serial_port *port, __u8 command,
 
 	command_port = port->serial->port[COMMAND_PORT];
 	command_info = usb_get_serial_port_data(command_port);
+
+	if (command_port->bulk_out_size < datasize + 1)
+		return -EIO;
+
 	mutex_lock(&command_info->mutex);
 	command_info->command_finished = false;