Commit message: virtio: validate config_len on load

Malformed input can have config_len in migration stream
exceed the array size allocated on destination, the
result will be heap overflow.

To fix, that config_len matches on both sides.

CVE-2014-0182

Reported-by: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

--

v2: use %ix and %zx to print config_len values
Signed-off-by: Juan Quintela <quintela@redhat.com>
CVE: CVE-2014-0182
CWE: CWE-119
Vulnerability description: Heap-based buffer overflow in the virtio_load function in hw/virtio/virtio.c in QEMU before 1.7.2 might allow remote attackers to execute arbitrary code via a crafted config length in a savevm image.

Project: qemu

 int virtio_load(VirtIODevice *vdev, QEMUFile *f)
 {
     int i, ret;
    int32_t config_len;
     uint32_t num;
     uint32_t features;
     uint32_t supported_features;
    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);

    if (k->load_config) {
        ret = k->load_config(qbus->parent, f);
        if (ret)
            return ret;
    }

    qemu_get_8s(f, &vdev->status);
    qemu_get_8s(f, &vdev->isr);
    qemu_get_be16s(f, &vdev->queue_sel);
    if (vdev->queue_sel >= VIRTIO_PCI_QUEUE_MAX) {
        return -1;
    }
    qemu_get_be32s(f, &features);

    if (virtio_set_features(vdev, features) < 0) {
        supported_features = k->get_features(qbus->parent);
        error_report("Features 0x%x unsupported. Allowed features: 0x%x",
                     features, supported_features);
                      features, supported_features);
         return -1;
     }
    config_len = qemu_get_be32(f);
    if (config_len != vdev->config_len) {
        error_report("Unexpected config length 0x%x. Expected 0x%zx",
                     config_len, vdev->config_len);
        return -1;
    }
     qemu_get_buffer(f, vdev->config, vdev->config_len);
 
     num = qemu_get_be32(f);
    for (i = 0; i < num; i++) {
        vdev->vq[i].vring.num = qemu_get_be32(f);
        if (k->has_variable_vring_alignment) {
            vdev->vq[i].vring.align = qemu_get_be32(f);
        }
        vdev->vq[i].pa = qemu_get_be64(f);
        qemu_get_be16s(f, &vdev->vq[i].last_avail_idx);
        vdev->vq[i].signalled_used_valid = false;
        vdev->vq[i].notification = true;

        if (vdev->vq[i].pa) {
            uint16_t nheads;
            virtqueue_init(&vdev->vq[i]);
            nheads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx;
            /* Check it isn't doing very strange things with descriptor numbers. */
            if (nheads > vdev->vq[i].vring.num) {
                error_report("VQ %d size 0x%x Guest index 0x%x "
                             "inconsistent with Host index 0x%x: delta 0x%x",
                             i, vdev->vq[i].vring.num,
                             vring_avail_idx(&vdev->vq[i]),
                             vdev->vq[i].last_avail_idx, nheads);
                return -1;
            }
        } else if (vdev->vq[i].last_avail_idx) {
            error_report("VQ %d address 0x0 "
                         "inconsistent with Host index 0x%x",
                         i, vdev->vq[i].last_avail_idx);
                return -1;
	}
        if (k->load_queue) {
            ret = k->load_queue(qbus->parent, i, f);
            if (ret)
                return ret;
        }
    }

    virtio_notify_vector(vdev, VIRTIO_NO_VECTOR);
    return 0;
}