static void control_work_handler(struct work_struct *work)
{
	struct ports_device *portdev;
	struct virtqueue *vq;
	struct port_buffer *buf;
	unsigned int len;

	portdev = container_of(work, struct ports_device, control_work);
	vq = portdev->c_ivq;

	spin_lock(&portdev->c_ivq_lock);
	while ((buf = virtqueue_get_buf(vq, &len))) {
		spin_unlock(&portdev->c_ivq_lock);

		buf->len = len;
		buf->offset = 0;

		handle_control_message(vq->vdev, portdev, buf);

		spin_lock(&portdev->c_ivq_lock);
		if (add_inbuf(portdev->c_ivq, buf) < 0) {
			dev_warn(&portdev->vdev->dev,
				 "Error adding buffer to queue\n");
			free_buf(buf, false);
		}
	}
	spin_unlock(&portdev->c_ivq_lock);
}
The program copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow.