static int tun_set_coalesce(struct net_device *dev,
			    struct ethtool_coalesce *ec)
{
	struct tun_struct *tun = netdev_priv(dev);

	if (ec->rx_max_coalesced_frames > NAPI_POLL_WEIGHT)
		tun->rx_batched = NAPI_POLL_WEIGHT;
	else
		tun->rx_batched = ec->rx_max_coalesced_frames;

	return 0;
}

The product dereferences a pointer that it expects to be valid but is NULL.