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>

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