static void tun_flow_flush(struct tun_struct *tun)
{
	int i;

	spin_lock_bh(&tun->lock);
	for (i = 0; i < TUN_NUM_FLOW_ENTRIES; i++) {
		struct tun_flow_entry *e;
		struct hlist_node *n;

		hlist_for_each_entry_safe(e, n, &tun->flows[i], hash_link)
			tun_flow_delete(tun, e);
	}
	spin_unlock_bh(&tun->lock);
}

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