static int tpacket_rcv(struct sk_buff *skb, struct net_device *dev,
		       struct packet_type *pt, struct net_device *orig_dev)
{
	struct sock *sk;
	struct packet_sock *po;
	struct sockaddr_ll *sll;
	union tpacket_uhdr h;
	u8 *skb_head = skb->data;
	int skb_len = skb->len;
	unsigned int snaplen, res;
	unsigned long status = TP_STATUS_USER;
	unsigned short macoff, netoff, hdrlen;
	struct sk_buff *copy_skb = NULL;
	struct timespec ts;
	__u32 ts_status;
	bool is_drop_n_account = false;

	/* struct tpacket{2,3}_hdr is aligned to a multiple of TPACKET_ALIGNMENT.
	 * We may add members to them until current aligned size without forcing
	 * userspace to call getsockopt(..., PACKET_HDRLEN, ...).
	 */
	BUILD_BUG_ON(TPACKET_ALIGN(sizeof(*h.h2)) != 32);
	BUILD_BUG_ON(TPACKET_ALIGN(sizeof(*h.h3)) != 48);

	if (skb->pkt_type == PACKET_LOOPBACK)
		goto drop;

	sk = pt->af_packet_priv;
	po = pkt_sk(sk);

	if (!net_eq(dev_net(dev), sock_net(sk)))
		goto drop;

	if (dev->header_ops) {
		if (sk->sk_type != SOCK_DGRAM)
			skb_push(skb, skb->data - skb_mac_header(skb));
		else if (skb->pkt_type == PACKET_OUTGOING) {
			/* Special case: outgoing packets have ll header at head */
			skb_pull(skb, skb_network_offset(skb));
		}
	}

	snaplen = skb->len;

	res = run_filter(skb, sk, snaplen);
	if (!res)
		goto drop_n_restore;

	if (skb->ip_summed == CHECKSUM_PARTIAL)
		status |= TP_STATUS_CSUMNOTREADY;
	else if (skb->pkt_type != PACKET_OUTGOING &&
		 (skb->ip_summed == CHECKSUM_COMPLETE ||
		  skb_csum_unnecessary(skb)))
		status |= TP_STATUS_CSUM_VALID;

	if (snaplen > res)
		snaplen = res;

	if (sk->sk_type == SOCK_DGRAM) {
		macoff = netoff = TPACKET_ALIGN(po->tp_hdrlen) + 16 +
				  po->tp_reserve;
	} else {
		unsigned int maclen = skb_network_offset(skb);
		netoff = TPACKET_ALIGN(po->tp_hdrlen +
				       (maclen < 16 ? 16 : maclen)) +
				       po->tp_reserve;
		if (po->has_vnet_hdr)
			netoff += sizeof(struct virtio_net_hdr);
		macoff = netoff - maclen;
	}
	if (po->tp_version <= TPACKET_V2) {
		if (macoff + snaplen > po->rx_ring.frame_size) {
			if (po->copy_thresh &&
			    atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf) {
				if (skb_shared(skb)) {
					copy_skb = skb_clone(skb, GFP_ATOMIC);
				} else {
					copy_skb = skb_get(skb);
					skb_head = skb->data;
				}
				if (copy_skb)
					skb_set_owner_r(copy_skb, sk);
			}
			snaplen = po->rx_ring.frame_size - macoff;
			if ((int)snaplen < 0)
				snaplen = 0;
		}
	} else if (unlikely(macoff + snaplen >
			    GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len)) {
		u32 nval;

		nval = GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len - macoff;
		pr_err_once("tpacket_rcv: packet too big, clamped from %u to %u. macoff=%u\n",
			    snaplen, nval, macoff);
		snaplen = nval;
		if (unlikely((int)snaplen < 0)) {
			snaplen = 0;
			macoff = GET_PBDQC_FROM_RB(&po->rx_ring)->max_frame_len;
		}
	}
	spin_lock(&sk->sk_receive_queue.lock);
	h.raw = packet_current_rx_frame(po, skb,
					TP_STATUS_KERNEL, (macoff+snaplen));
	if (!h.raw)
		goto drop_n_account;
	if (po->tp_version <= TPACKET_V2) {
		packet_increment_rx_head(po, &po->rx_ring);
	/*
	 * LOSING will be reported till you read the stats,
	 * because it's COR - Clear On Read.
	 * Anyways, moving it for V1/V2 only as V3 doesn't need this
	 * at packet level.
	 */
		if (po->stats.stats1.tp_drops)
			status |= TP_STATUS_LOSING;
	}
	po->stats.stats1.tp_packets++;
	if (copy_skb) {
		status |= TP_STATUS_COPY;
		__skb_queue_tail(&sk->sk_receive_queue, copy_skb);
	}
	spin_unlock(&sk->sk_receive_queue.lock);

	if (po->has_vnet_hdr) {
		if (__packet_rcv_vnet(skb, h.raw + macoff -
					   sizeof(struct virtio_net_hdr))) {
			spin_lock(&sk->sk_receive_queue.lock);
			goto drop_n_account;
		}
	}

	skb_copy_bits(skb, 0, h.raw + macoff, snaplen);

	if (!(ts_status = tpacket_get_timestamp(skb, &ts, po->tp_tstamp)))
		getnstimeofday(&ts);

	status |= ts_status;

	switch (po->tp_version) {
	case TPACKET_V1:
		h.h1->tp_len = skb->len;
		h.h1->tp_snaplen = snaplen;
		h.h1->tp_mac = macoff;
		h.h1->tp_net = netoff;
		h.h1->tp_sec = ts.tv_sec;
		h.h1->tp_usec = ts.tv_nsec / NSEC_PER_USEC;
		hdrlen = sizeof(*h.h1);
		break;
	case TPACKET_V2:
		h.h2->tp_len = skb->len;
		h.h2->tp_snaplen = snaplen;
		h.h2->tp_mac = macoff;
		h.h2->tp_net = netoff;
		h.h2->tp_sec = ts.tv_sec;
		h.h2->tp_nsec = ts.tv_nsec;
		if (skb_vlan_tag_present(skb)) {
			h.h2->tp_vlan_tci = skb_vlan_tag_get(skb);
			h.h2->tp_vlan_tpid = ntohs(skb->vlan_proto);
			status |= TP_STATUS_VLAN_VALID | TP_STATUS_VLAN_TPID_VALID;
		} else {
			h.h2->tp_vlan_tci = 0;
			h.h2->tp_vlan_tpid = 0;
		}
		memset(h.h2->tp_padding, 0, sizeof(h.h2->tp_padding));
		hdrlen = sizeof(*h.h2);
		break;
	case TPACKET_V3:
		/* tp_nxt_offset,vlan are already populated above.
		 * So DONT clear those fields here
		 */
		h.h3->tp_status |= status;
		h.h3->tp_len = skb->len;
		h.h3->tp_snaplen = snaplen;
		h.h3->tp_mac = macoff;
		h.h3->tp_net = netoff;
		h.h3->tp_sec  = ts.tv_sec;
		h.h3->tp_nsec = ts.tv_nsec;
		memset(h.h3->tp_padding, 0, sizeof(h.h3->tp_padding));
		hdrlen = sizeof(*h.h3);
		break;
	default:
		BUG();
	}

	sll = h.raw + TPACKET_ALIGN(hdrlen);
	sll->sll_halen = dev_parse_header(skb, sll->sll_addr);
	sll->sll_family = AF_PACKET;
	sll->sll_hatype = dev->type;
	sll->sll_protocol = skb->protocol;
	sll->sll_pkttype = skb->pkt_type;
	if (unlikely(po->origdev))
		sll->sll_ifindex = orig_dev->ifindex;
	else
		sll->sll_ifindex = dev->ifindex;

	smp_mb();

#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE == 1
	if (po->tp_version <= TPACKET_V2) {
		u8 *start, *end;

		end = (u8 *) PAGE_ALIGN((unsigned long) h.raw +
					macoff + snaplen);

		for (start = h.raw; start < end; start += PAGE_SIZE)
			flush_dcache_page(pgv_to_page(start));
	}
	smp_wmb();
#endif

	if (po->tp_version <= TPACKET_V2) {
		__packet_set_status(po, h.raw, status);
		sk->sk_data_ready(sk);
	} else {
		prb_clear_blk_fill_status(&po->rx_ring);
	}

drop_n_restore:
	if (skb_head != skb->data && skb_shared(skb)) {
		skb->data = skb_head;
		skb->len = skb_len;
	}
drop:
	if (!is_drop_n_account)
		consume_skb(skb);
	else
		kfree_skb(skb);
	return 0;

drop_n_account:
	is_drop_n_account = true;
	po->stats.stats1.tp_drops++;
	spin_unlock(&sk->sk_receive_queue.lock);

	sk->sk_data_ready(sk);
	kfree_skb(copy_skb);
	goto drop_n_restore;
}

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.