int skb_append_datato_frags(struct sock *sk, struct sk_buff *skb,
			int (*getfrag)(void *from, char *to, int offset,
					int len, int odd, struct sk_buff *skb),
			void *from, int length)
{
	int frg_cnt = skb_shinfo(skb)->nr_frags;
	int copy;
	int offset = 0;
	int ret;
	struct page_frag *pfrag = &current->task_frag;

	do {
		/* Return error if we don't have space for new frag */
		if (frg_cnt >= MAX_SKB_FRAGS)
			return -EMSGSIZE;

		if (!sk_page_frag_refill(sk, pfrag))
			return -ENOMEM;

		/* copy the user data to page */
		copy = min_t(int, length, pfrag->size - pfrag->offset);

		ret = getfrag(from, page_address(pfrag->page) + pfrag->offset,
			      offset, copy, 0, skb);
		if (ret < 0)
			return -EFAULT;

		/* copy was successful so update the size parameters */
		skb_fill_page_desc(skb, frg_cnt, pfrag->page, pfrag->offset,
				   copy);
		frg_cnt++;
		pfrag->offset += copy;
		get_page(pfrag->page);

		skb->truesize += copy;
		atomic_add(copy, &sk->sk_wmem_alloc);
		skb->len += copy;
		skb->data_len += copy;
		offset += copy;
		length -= copy;

	} while (length > 0);

	return 0;
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.