struct sk_buff *sctp_skb_recv_datagram(struct sock *sk, int flags,
				       int noblock, int *err)
{
	int error;
	struct sk_buff *skb;
	long timeo;

	timeo = sock_rcvtimeo(sk, noblock);

	pr_debug("%s: timeo:%ld, max:%ld\n", __func__, timeo,
		 MAX_SCHEDULE_TIMEOUT);

	do {
		/* Again only user level code calls this function,
		 * so nothing interrupt level
		 * will suddenly eat the receive_queue.
		 *
		 *  Look at current nfs client by the way...
		 *  However, this function was correct in any case. 8)
		 */
		if (flags & MSG_PEEK) {
			skb = skb_peek(&sk->sk_receive_queue);
			if (skb)
				refcount_inc(&skb->users);
		} else {
			skb = __skb_dequeue(&sk->sk_receive_queue);
		}

		if (skb)
			return skb;

		/* Caller is allowed not to check sk->sk_err before calling. */
		error = sock_error(sk);
		if (error)
			goto no_packet;

		if (sk->sk_shutdown & RCV_SHUTDOWN)
			break;

		if (sk_can_busy_loop(sk)) {
			sk_busy_loop(sk, noblock);

			if (!skb_queue_empty(&sk->sk_receive_queue))
				continue;
		}

		/* User doesn't want to wait.  */
		error = -EAGAIN;
		if (!timeo)
			goto no_packet;
	} while (sctp_wait_for_packet(sk, err, &timeo) == 0);

	return NULL;

no_packet:
	*err = error;
	return NULL;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.