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

[Juan Quintela <quintela@redhat.com>]

Juan Quintela <quintela@redhat.com> wrote:
> "Michael S. Tsirkin" <mst@redhat.com> 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" <dgilbert@redhat.com>
>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>> ---
>>  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.

After discussing with michael, left it as int32_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/

and use here "%ix   .... %zx"

Later, Juan.

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