static int __packet_rcv_has_room(struct packet_sock *po, struct sk_buff *skb)
{
	struct sock *sk = &po->sk;
	int ret = ROOM_NONE;

	if (po->prot_hook.func != tpacket_rcv) {
		int avail = sk->sk_rcvbuf - atomic_read(&sk->sk_rmem_alloc)
					  - (skb ? skb->truesize : 0);
		if (avail > (sk->sk_rcvbuf >> ROOM_POW_OFF))
			return ROOM_NORMAL;
		else if (avail > 0)
			return ROOM_LOW;
		else
			return ROOM_NONE;
	}

	if (po->tp_version == TPACKET_V3) {
		if (__tpacket_v3_has_room(po, ROOM_POW_OFF))
			ret = ROOM_NORMAL;
		else if (__tpacket_v3_has_room(po, 0))
			ret = ROOM_LOW;
	} else {
		if (__tpacket_has_room(po, ROOM_POW_OFF))
			ret = ROOM_NORMAL;
		else if (__tpacket_has_room(po, 0))
			ret = ROOM_LOW;
	}

	return ret;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.