static struct sk_buff *netlink_trim(struct sk_buff *skb, gfp_t allocation)
{
	int delta;

	WARN_ON(skb->sk != NULL);
	if (netlink_skb_is_mmaped(skb))
		return skb;

	delta = skb->end - skb->tail;
	if (is_vmalloc_addr(skb->head) || delta * 2 < skb->truesize)
		return skb;

	if (skb_shared(skb)) {
		struct sk_buff *nskb = skb_clone(skb, allocation);
		if (!nskb)
			return skb;
		consume_skb(skb);
		skb = nskb;
	}

	if (!pskb_expand_head(skb, 0, -delta, allocation))
		skb->truesize -= delta;

	return skb;
}

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.