static void mISDN_sock_unlink(struct mISDN_sock_list *l, struct sock *sk)
{
	write_lock_bh(&l->lock);
	sk_del_node_init(sk);
	write_unlock_bh(&l->lock);
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.