static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
{
    VirtIONet *n = q->n;
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    VirtQueueElement elem;
    int32_t num_packets = 0;
    int queue_index = vq2q(virtio_get_queue_index(q->tx_vq));
    if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
        return num_packets;
    }

    assert(vdev->vm_running);

    if (q->async_tx.elem.out_num) {
        virtio_queue_set_notification(q->tx_vq, 0);
        return num_packets;
    }

    while (virtqueue_pop(q->tx_vq, &elem)) {
        ssize_t ret, len;
        unsigned int out_num = elem.out_num;
        struct iovec *out_sg = &elem.out_sg[0];
        struct iovec sg[VIRTQUEUE_MAX_SIZE];

        if (out_num < 1) {
            error_report("virtio-net header not in first element");
            exit(1);
        }

        /*
         * If host wants to see the guest header as is, we can
         * pass it on unchanged. Otherwise, copy just the parts
         * that host is interested in.
         */
        assert(n->host_hdr_len <= n->guest_hdr_len);
        if (n->host_hdr_len != n->guest_hdr_len) {
            unsigned sg_num = iov_copy(sg, ARRAY_SIZE(sg),
                                       out_sg, out_num,
                                       0, n->host_hdr_len);
            sg_num += iov_copy(sg + sg_num, ARRAY_SIZE(sg) - sg_num,
                             out_sg, out_num,
                             n->guest_hdr_len, -1);
            out_num = sg_num;
            out_sg = sg;
        }

        len = n->guest_hdr_len;

        ret = qemu_sendv_packet_async(qemu_get_subqueue(n->nic, queue_index),
                                      out_sg, out_num, virtio_net_tx_complete);
        if (ret == 0) {
            virtio_queue_set_notification(q->tx_vq, 0);
            q->async_tx.elem = elem;
            q->async_tx.len  = len;
            return -EBUSY;
        }

        len += ret;

        virtqueue_push(q->tx_vq, &elem, 0);
        virtio_notify(vdev, q->tx_vq);

        if (++num_packets >= n->tx_burst) {
            break;
        }
    }
    return num_packets;
}

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.