void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err)
{
	struct sk_buff *skb;
	struct nlmsghdr *rep;
	struct nlmsgerr *errmsg;
	size_t payload = sizeof(*errmsg);

	/* error messages get the original request appened */
	if (err)
		payload += nlmsg_len(nlh);

	skb = netlink_alloc_skb(in_skb->sk, nlmsg_total_size(payload),
				NETLINK_CB(in_skb).portid, GFP_KERNEL);
	if (!skb) {
		struct sock *sk;

		sk = netlink_lookup(sock_net(in_skb->sk),
				    in_skb->sk->sk_protocol,
				    NETLINK_CB(in_skb).portid);
		if (sk) {
			sk->sk_err = ENOBUFS;
			sk->sk_error_report(sk);
			sock_put(sk);
		}
		return;
	}

	rep = __nlmsg_put(skb, NETLINK_CB(in_skb).portid, nlh->nlmsg_seq,
			  NLMSG_ERROR, payload, 0);
	errmsg = nlmsg_data(rep);
	errmsg->error = err;
	memcpy(&errmsg->msg, nlh, err ? nlh->nlmsg_len : sizeof(*nlh));
	netlink_unicast(in_skb->sk, skb, NETLINK_CB(in_skb).portid, MSG_DONTWAIT);
}

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.