Commit message: virtio-net: out-of-bounds buffer write on load

CVE-2013-4149 QEMU 1.3.0 out-of-bounds buffer write in
virtio_net_load()@hw/net/virtio-net.c

>         } else if (n->mac_table.in_use) {
>             uint8_t *buf = g_malloc0(n->mac_table.in_use);

We are allocating buffer of size n->mac_table.in_use

>             qemu_get_buffer(f, buf, n->mac_table.in_use * ETH_ALEN);

and read to the n->mac_table.in_use size buffer n->mac_table.in_use *
ETH_ALEN bytes, corrupting memory.

If adversary controls state then memory written there is controlled
by adversary.

Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
CVE: CVE-2013-4149
CWE: CWE-119
Vulnerability description: Buffer overflow in virtio_net_load function in net/virtio-net.c in QEMU 1.3.0 through 1.7.x before 1.7.2 might allow remote attackers to execute arbitrary code via a large MAC table.

Project: qemu
File: virtio-net.c

static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
{
    VirtIONet *n = opaque;
    VirtIODevice *vdev = VIRTIO_DEVICE(n);
    int ret, i, link_down;

    if (version_id < 2 || version_id > VIRTIO_NET_VM_VERSION)
        return -EINVAL;

    ret = virtio_load(vdev, f);
    if (ret) {
        return ret;
    }

    qemu_get_buffer(f, n->mac, ETH_ALEN);
    n->vqs[0].tx_waiting = qemu_get_be32(f);

    virtio_net_set_mrg_rx_bufs(n, qemu_get_be32(f));

    if (version_id >= 3)
        n->status = qemu_get_be16(f);

    if (version_id >= 4) {
        if (version_id < 8) {
            n->promisc = qemu_get_be32(f);
            n->allmulti = qemu_get_be32(f);
        } else {
            n->promisc = qemu_get_byte(f);
            n->allmulti = qemu_get_byte(f);
        }
    }

    if (version_id >= 5) {
        n->mac_table.in_use = qemu_get_be32(f);
        /* MAC_TABLE_ENTRIES may be different from the saved image */
        if (n->mac_table.in_use <= MAC_TABLE_ENTRIES) {
            qemu_get_buffer(f, n->mac_table.macs,
                            n->mac_table.in_use * ETH_ALEN);
        } else if (n->mac_table.in_use) {
            uint8_t *buf = g_malloc0(n->mac_table.in_use);
            qemu_get_buffer(f, buf, n->mac_table.in_use * ETH_ALEN);
            g_free(buf);
            n->mac_table.multi_overflow = n->mac_table.uni_overflow = 1;
            n->mac_table.in_use = 0;
        }
    }
 
    if (version_id >= 6)
        qemu_get_buffer(f, (uint8_t *)n->vlans, MAX_VLAN >> 3);

    if (version_id >= 7) {
        if (qemu_get_be32(f) && !peer_has_vnet_hdr(n)) {
            error_report("virtio-net: saved image requires vnet_hdr=on");
            return -1;
        }
    }

    if (version_id >= 9) {
        n->mac_table.multi_overflow = qemu_get_byte(f);
        n->mac_table.uni_overflow = qemu_get_byte(f);
    }

    if (version_id >= 10) {
        n->alluni = qemu_get_byte(f);
        n->nomulti = qemu_get_byte(f);
        n->nouni = qemu_get_byte(f);
        n->nobcast = qemu_get_byte(f);
    }

    if (version_id >= 11) {
        if (qemu_get_byte(f) && !peer_has_ufo(n)) {
            error_report("virtio-net: saved image requires TUN_F_UFO support");
            return -1;
        }
    }

    if (n->max_queues > 1) {
        if (n->max_queues != qemu_get_be16(f)) {
            error_report("virtio-net: different max_queues ");
            return -1;
        }

        n->curr_queues = qemu_get_be16(f);
        if (n->curr_queues > n->max_queues) {
            error_report("virtio-net: curr_queues %x > max_queues %x",
                         n->curr_queues, n->max_queues);
            return -1;
        }
        for (i = 1; i < n->curr_queues; i++) {
            n->vqs[i].tx_waiting = qemu_get_be32(f);
        }
    }

    if ((1 << VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) & vdev->guest_features) {
        n->curr_guest_offloads = qemu_get_be64(f);
    } else {
        n->curr_guest_offloads = virtio_net_supported_guest_offloads(n);
    }

    if (peer_has_vnet_hdr(n)) {
        virtio_net_apply_guest_offloads(n);
    }

    virtio_net_set_queues(n);

    /* Find the first multicast entry in the saved MAC filter */
    for (i = 0; i < n->mac_table.in_use; i++) {
        if (n->mac_table.macs[i * ETH_ALEN] & 1) {
            break;
        }
    }
    n->mac_table.first_multi = i;

    /* nc.link_down can't be migrated, so infer link_down according
     * to link status bit in n->status */
    link_down = (n->status & VIRTIO_NET_S_LINK_UP) == 0;
    for (i = 0; i < n->max_queues; i++) {
        qemu_get_subqueue(n->nic, i)->link_down = link_down;
    }

    return 0;
}