static void handle_control_message(struct virtio_device *vdev,
				   struct ports_device *portdev,
				   struct port_buffer *buf)
{
	struct virtio_console_control *cpkt;
	struct port *port;
	size_t name_size;
	int err;

	cpkt = (struct virtio_console_control *)(buf->buf + buf->offset);

	port = find_port_by_id(portdev, virtio32_to_cpu(vdev, cpkt->id));
	if (!port &&
	    cpkt->event != cpu_to_virtio16(vdev, VIRTIO_CONSOLE_PORT_ADD)) {
		/* No valid header at start of buffer.  Drop it. */
		dev_dbg(&portdev->vdev->dev,
			"Invalid index %u in control packet\n", cpkt->id);
		return;
	}

	switch (virtio16_to_cpu(vdev, cpkt->event)) {
	case VIRTIO_CONSOLE_PORT_ADD:
		if (port) {
			dev_dbg(&portdev->vdev->dev,
				"Port %u already added\n", port->id);
			send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
			break;
		}
		if (virtio32_to_cpu(vdev, cpkt->id) >=
		    portdev->max_nr_ports) {
			dev_warn(&portdev->vdev->dev,
				"Request for adding port with "
				"out-of-bound id %u, max. supported id: %u\n",
				cpkt->id, portdev->max_nr_ports - 1);
			break;
		}
		add_port(portdev, virtio32_to_cpu(vdev, cpkt->id));
		break;
	case VIRTIO_CONSOLE_PORT_REMOVE:
		unplug_port(port);
		break;
	case VIRTIO_CONSOLE_CONSOLE_PORT:
		if (!cpkt->value)
			break;
		if (is_console_port(port))
			break;

		init_port_console(port);
		complete(&early_console_added);
		/*
		 * Could remove the port here in case init fails - but
		 * have to notify the host first.
		 */
		break;
	case VIRTIO_CONSOLE_RESIZE: {
		struct {
			__u16 rows;
			__u16 cols;
		} size;

		if (!is_console_port(port))
			break;

		memcpy(&size, buf->buf + buf->offset + sizeof(*cpkt),
		       sizeof(size));
		set_console_size(port, size.rows, size.cols);

		port->cons.hvc->irq_requested = 1;
		resize_console(port);
		break;
	}
	case VIRTIO_CONSOLE_PORT_OPEN:
		port->host_connected = virtio16_to_cpu(vdev, cpkt->value);
		wake_up_interruptible(&port->waitqueue);
		/*
		 * If the host port got closed and the host had any
		 * unconsumed buffers, we'll be able to reclaim them
		 * now.
		 */
		spin_lock_irq(&port->outvq_lock);
		reclaim_consumed_buffers(port);
		spin_unlock_irq(&port->outvq_lock);

		/*
		 * If the guest is connected, it'll be interested in
		 * knowing the host connection state changed.
		 */
		spin_lock_irq(&port->inbuf_lock);
		send_sigio_to_port(port);
		spin_unlock_irq(&port->inbuf_lock);
		break;
	case VIRTIO_CONSOLE_PORT_NAME:
		/*
		 * If we woke up after hibernation, we can get this
		 * again.  Skip it in that case.
		 */
		if (port->name)
			break;

		/*
		 * Skip the size of the header and the cpkt to get the size
		 * of the name that was sent
		 */
		name_size = buf->len - buf->offset - sizeof(*cpkt) + 1;

		port->name = kmalloc(name_size, GFP_KERNEL);
		if (!port->name) {
			dev_err(port->dev,
				"Not enough space to store port name\n");
			break;
		}
		strncpy(port->name, buf->buf + buf->offset + sizeof(*cpkt),
			name_size - 1);
		port->name[name_size - 1] = 0;

		/*
		 * Since we only have one sysfs attribute, 'name',
		 * create it only if we have a name for the port.
		 */
		err = sysfs_create_group(&port->dev->kobj,
					 &port_attribute_group);
		if (err) {
			dev_err(port->dev,
				"Error %d creating sysfs device attributes\n",
				err);
		} else {
			/*
			 * Generate a udev event so that appropriate
			 * symlinks can be created based on udev
			 * rules.
			 */
			kobject_uevent(&port->dev->kobj, KOBJ_CHANGE);
		}
		break;
	}
}

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.