static int pppoe_connect(struct socket *sock, struct sockaddr *uservaddr,
		  int sockaddr_len, int flags)
{
	struct sock *sk = sock->sk;
	struct sockaddr_pppox *sp = (struct sockaddr_pppox *)uservaddr;
	struct pppox_sock *po = pppox_sk(sk);
	struct net_device *dev = NULL;
	struct pppoe_net *pn;
	struct net *net = NULL;
	int error;

	lock_sock(sk);

	error = -EINVAL;
	if (sp->sa_protocol != PX_PROTO_OE)
		goto end;

	/* Check for already bound sockets */
	error = -EBUSY;
	if ((sk->sk_state & PPPOX_CONNECTED) &&
	     stage_session(sp->sa_addr.pppoe.sid))
		goto end;

	/* Check for already disconnected sockets, on attempts to disconnect */
	error = -EALREADY;
	if ((sk->sk_state & PPPOX_DEAD) &&
	     !stage_session(sp->sa_addr.pppoe.sid))
		goto end;

	error = 0;

	/* Delete the old binding */
	if (stage_session(po->pppoe_pa.sid)) {
		pppox_unbind_sock(sk);
		pn = pppoe_pernet(sock_net(sk));
		delete_item(pn, po->pppoe_pa.sid,
			    po->pppoe_pa.remote, po->pppoe_ifindex);
		if (po->pppoe_dev) {
			dev_put(po->pppoe_dev);
			po->pppoe_dev = NULL;
		}

		memset(sk_pppox(po) + 1, 0,
		       sizeof(struct pppox_sock) - sizeof(struct sock));
		sk->sk_state = PPPOX_NONE;
	}

	/* Re-bind in session stage only */
	if (stage_session(sp->sa_addr.pppoe.sid)) {
		error = -ENODEV;
		net = sock_net(sk);
		dev = dev_get_by_name(net, sp->sa_addr.pppoe.dev);
		if (!dev)
			goto err_put;

		po->pppoe_dev = dev;
		po->pppoe_ifindex = dev->ifindex;
		pn = pppoe_pernet(net);
		if (!(dev->flags & IFF_UP)) {
			goto err_put;
		}

		memcpy(&po->pppoe_pa,
		       &sp->sa_addr.pppoe,
		       sizeof(struct pppoe_addr));

		write_lock_bh(&pn->hash_lock);
		error = __set_item(pn, po);
		write_unlock_bh(&pn->hash_lock);
		if (error < 0)
			goto err_put;

		po->chan.hdrlen = (sizeof(struct pppoe_hdr) +
				   dev->hard_header_len);

		po->chan.mtu = dev->mtu - sizeof(struct pppoe_hdr);
		po->chan.private = sk;
		po->chan.ops = &pppoe_chan_ops;

		error = ppp_register_net_channel(dev_net(dev), &po->chan);
		if (error) {
			delete_item(pn, po->pppoe_pa.sid,
				    po->pppoe_pa.remote, po->pppoe_ifindex);
			goto err_put;
		}

		sk->sk_state = PPPOX_CONNECTED;
	}

	po->num = sp->sa_addr.pppoe.sid;

end:
	release_sock(sk);
	return error;
err_put:
	if (po->pppoe_dev) {
		dev_put(po->pppoe_dev);
		po->pppoe_dev = NULL;
	}
	goto end;
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.