static struct dst_entry *ip6_sk_dst_check(struct sock *sk,
					  struct dst_entry *dst,
 					  const struct flowi6 *fl6)
 {
 	struct ipv6_pinfo *np = inet6_sk(sk);
	struct rt6_info *rt = (struct rt6_info *)dst;
 
 	if (!dst)
 		goto out;
 
 	/* Yes, checking route validity in not connected
 	 * case is not very simple. Take into account,
 	 * that we do not support routing by source, TOS,
	 * and MSG_DONTROUTE 		--ANK (980726)
	 *
	 * 1. ip6_rt_check(): If route was host route,
	 *    check that cached destination is current.
	 *    If it is network route, we still may
	 *    check its validity using saved pointer
	 *    to the last used address: daddr_cache.
	 *    We do not want to save whole address now,
	 *    (because main consumer of this service
	 *    is tcp, which has not this problem),
	 *    so that the last trick works only on connected
	 *    sockets.
	 * 2. oif also should be the same.
	 */
	if (ip6_rt_check(&rt->rt6i_dst, &fl6->daddr, np->daddr_cache) ||
#ifdef CONFIG_IPV6_SUBTREES
	    ip6_rt_check(&rt->rt6i_src, &fl6->saddr, np->saddr_cache) ||
#endif
	    (fl6->flowi6_oif && fl6->flowi6_oif != dst->dev->ifindex)) {
		dst_release(dst);
		dst = NULL;
	}

out:
	return dst;
}

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.