Re: [Qemu-devel] [PATCH v6 4/5] virtio: validate config_len on load

[Juan Quintela]

"Michael S. Tsirkin" <address@hidden> wrote:
> 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" <address@hidden>
> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
>  hw/virtio/virtio.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 3bad71e..0d5d368 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -898,6 +898,7 @@ int virtio_set_features(VirtIODevice *vdev, uint32_t val)
>  int virtio_load(VirtIODevice *vdev, QEMUFile *f)
>  {
>      int i, ret;
> +    int32_t config_len;

Has a warning.

/mnt/kvm/qemu/next/hw/virtio/virtio.c: In function ‘virtio_load’:
/mnt/kvm/qemu/next/hw/virtio/virtio.c:931:22: error: format ‘%i’ expects 
argument of type ‘int’, but argument 2 has type ‘size_t’ [-Werror=format=]
                      config_len, vdev->config_len);
                      ^

changing config_len to size_t.

>      uint32_t num;
>      uint32_t features;
>      uint32_t supported_features;
> @@ -924,7 +925,12 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f)
>                       features, supported_features);
>          return -1;
>      }
> -    vdev->config_len = qemu_get_be32(f);
> +    config_len = qemu_get_be32(f);
> +    if (config_len != vdev->config_len) {
> +        error_report("Unexpected config length 0x%x. Expected 0x%x",

and this to:

s/%x/%zx/

Later, Juan.


> +                     config_len, vdev->config_len);
> +        return -1;
> +    }
>      qemu_get_buffer(f, vdev->config, vdev->config_len);
>  
>      num = qemu_get_be32(f);