static int packet_rcv_fanout(struct sk_buff *skb, struct net_device *dev,
			     struct packet_type *pt, struct net_device *orig_dev)
{
	struct packet_fanout *f = pt->af_packet_priv;
	unsigned int num = READ_ONCE(f->num_members);
	struct net *net = read_pnet(&f->net);
	struct packet_sock *po;
	unsigned int idx;

	if (!net_eq(dev_net(dev), net) || !num) {
		kfree_skb(skb);
		return 0;
	}

	if (fanout_has_flag(f, PACKET_FANOUT_FLAG_DEFRAG)) {
		skb = ip_check_defrag(net, skb, IP_DEFRAG_AF_PACKET);
		if (!skb)
			return 0;
	}
	switch (f->type) {
	case PACKET_FANOUT_HASH:
	default:
		idx = fanout_demux_hash(f, skb, num);
		break;
	case PACKET_FANOUT_LB:
		idx = fanout_demux_lb(f, skb, num);
		break;
	case PACKET_FANOUT_CPU:
		idx = fanout_demux_cpu(f, skb, num);
		break;
	case PACKET_FANOUT_RND:
		idx = fanout_demux_rnd(f, skb, num);
		break;
	case PACKET_FANOUT_QM:
		idx = fanout_demux_qm(f, skb, num);
		break;
	case PACKET_FANOUT_ROLLOVER:
		idx = fanout_demux_rollover(f, skb, 0, false, num);
		break;
	case PACKET_FANOUT_CBPF:
	case PACKET_FANOUT_EBPF:
		idx = fanout_demux_bpf(f, skb, num);
		break;
	}

	if (fanout_has_flag(f, PACKET_FANOUT_FLAG_ROLLOVER))
		idx = fanout_demux_rollover(f, skb, idx, true, num);

	po = pkt_sk(f->arr[idx]);
	return po->prot_hook.func(skb, dev, &po->prot_hook, orig_dev);
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.