Commit message: l2tp: fix info leak via getsockname()

The L2TP code for IPv6 fails to initialize the l2tp_unused member of
struct sockaddr_l2tpip6 and that for leaks two bytes kernel stack via
the getsockname() syscall. Initialize l2tp_unused with 0 to avoid the
info leak.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Cc: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
CVE: CVE-2012-6543
CWE: CWE-200
Vulnerability description: The l2tp_ip6_getname function in net/l2tp/l2tp_ip6.c in the Linux kernel before 3.6 does not initialize a certain structure member, which allows local users to obtain sensitive information from kernel stack memory via a crafted application.

Project: linux
File: l2tp_ip6.c

static struct sock *__l2tp_ip6_bind_lookup(struct net *net,
					   struct in6_addr *laddr,
					   int dif, u32 tunnel_id)
{
	struct hlist_node *node;
	struct sock *sk;

	sk_for_each_bound(sk, node, &l2tp_ip6_bind_table) {
		struct in6_addr *addr = inet6_rcv_saddr(sk);
		struct l2tp_ip6_sock *l2tp = l2tp_ip6_sk(sk);

		if (l2tp == NULL)
			continue;

		if ((l2tp->conn_id == tunnel_id) &&
		    net_eq(sock_net(sk), net) &&
		    !(addr && ipv6_addr_equal(addr, laddr)) &&
		    !(sk->sk_bound_dev_if && sk->sk_bound_dev_if != dif))
			goto found;
	}

	sk = NULL;
found:
	return sk;
}

Project: linux
File: l2tp_ip6.c

static void l2tp_ip6_destroy_sock(struct sock *sk)
{
	lock_sock(sk);
	ip6_flush_pending_frames(sk);
	release_sock(sk);

	inet6_destroy_sock(sk);
}

Project: linux
File: l2tp_ip6.c

static int l2tp_ip6_recvmsg(struct kiocb *iocb, struct sock *sk,
			    struct msghdr *msg, size_t len, int noblock,
			    int flags, int *addr_len)
{
	struct inet_sock *inet = inet_sk(sk);
	struct sockaddr_l2tpip6 *lsa = (struct sockaddr_l2tpip6 *)msg->msg_name;
	size_t copied = 0;
	int err = -EOPNOTSUPP;
	struct sk_buff *skb;

	if (flags & MSG_OOB)
		goto out;

	if (addr_len)
		*addr_len = sizeof(*lsa);

	if (flags & MSG_ERRQUEUE)
		return ipv6_recv_error(sk, msg, len);

	skb = skb_recv_datagram(sk, flags, noblock, &err);
	if (!skb)
		goto out;

	copied = skb->len;
	if (len < copied) {
		msg->msg_flags |= MSG_TRUNC;
		copied = len;
	}

	err = skb_copy_datagram_iovec(skb, 0, msg->msg_iov, copied);
	if (err)
		goto done;

	sock_recv_timestamp(msg, sk, skb);

	/* Copy the address. */
	if (lsa) {
		lsa->l2tp_family = AF_INET6;
		lsa->l2tp_unused = 0;
		lsa->l2tp_addr = ipv6_hdr(skb)->saddr;
		lsa->l2tp_flowinfo = 0;
		lsa->l2tp_scope_id = 0;
		if (ipv6_addr_type(&lsa->l2tp_addr) & IPV6_ADDR_LINKLOCAL)
			lsa->l2tp_scope_id = IP6CB(skb)->iif;
	}

	if (inet->cmsg_flags)
		ip_cmsg_recv(msg, skb);

	if (flags & MSG_TRUNC)
		copied = skb->len;
done:
	skb_free_datagram(sk, skb);
out:
	return err ? err : copied;
}

Project: linux
File: l2tp_ip6.c

static int l2tp_ip6_sendmsg(struct kiocb *iocb, struct sock *sk,
			    struct msghdr *msg, size_t len)
{
	struct ipv6_txoptions opt_space;
	struct sockaddr_l2tpip6 *lsa =
		(struct sockaddr_l2tpip6 *) msg->msg_name;
	struct in6_addr *daddr, *final_p, final;
	struct ipv6_pinfo *np = inet6_sk(sk);
	struct ipv6_txoptions *opt = NULL;
	struct ip6_flowlabel *flowlabel = NULL;
	struct dst_entry *dst = NULL;
	struct flowi6 fl6;
	int addr_len = msg->msg_namelen;
	int hlimit = -1;
	int tclass = -1;
	int dontfrag = -1;
	int transhdrlen = 4; /* zero session-id */
	int ulen = len + transhdrlen;
	int err;

	/* Rough check on arithmetic overflow,
	   better check is made in ip6_append_data().
	 */
	if (len > INT_MAX)
		return -EMSGSIZE;

	/* Mirror BSD error message compatibility */
	if (msg->msg_flags & MSG_OOB)
		return -EOPNOTSUPP;

	/*
	 *	Get and verify the address.
	 */
	memset(&fl6, 0, sizeof(fl6));

	fl6.flowi6_mark = sk->sk_mark;

	if (lsa) {
		if (addr_len < SIN6_LEN_RFC2133)
			return -EINVAL;

		if (lsa->l2tp_family && lsa->l2tp_family != AF_INET6)
			return -EAFNOSUPPORT;

		daddr = &lsa->l2tp_addr;
		if (np->sndflow) {
			fl6.flowlabel = lsa->l2tp_flowinfo & IPV6_FLOWINFO_MASK;
			if (fl6.flowlabel&IPV6_FLOWLABEL_MASK) {
				flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
				if (flowlabel == NULL)
					return -EINVAL;
				daddr = &flowlabel->dst;
			}
		}

		/*
		 * Otherwise it will be difficult to maintain
		 * sk->sk_dst_cache.
		 */
		if (sk->sk_state == TCP_ESTABLISHED &&
		    ipv6_addr_equal(daddr, &np->daddr))
			daddr = &np->daddr;

		if (addr_len >= sizeof(struct sockaddr_in6) &&
		    lsa->l2tp_scope_id &&
		    ipv6_addr_type(daddr) & IPV6_ADDR_LINKLOCAL)
			fl6.flowi6_oif = lsa->l2tp_scope_id;
	} else {
		if (sk->sk_state != TCP_ESTABLISHED)
			return -EDESTADDRREQ;

		daddr = &np->daddr;
		fl6.flowlabel = np->flow_label;
	}

	if (fl6.flowi6_oif == 0)
		fl6.flowi6_oif = sk->sk_bound_dev_if;

	if (msg->msg_controllen) {
		opt = &opt_space;
		memset(opt, 0, sizeof(struct ipv6_txoptions));
		opt->tot_len = sizeof(struct ipv6_txoptions);

		err = datagram_send_ctl(sock_net(sk), sk, msg, &fl6, opt,
					&hlimit, &tclass, &dontfrag);
		if (err < 0) {
			fl6_sock_release(flowlabel);
			return err;
		}
		if ((fl6.flowlabel & IPV6_FLOWLABEL_MASK) && !flowlabel) {
			flowlabel = fl6_sock_lookup(sk, fl6.flowlabel);
			if (flowlabel == NULL)
				return -EINVAL;
		}
		if (!(opt->opt_nflen|opt->opt_flen))
			opt = NULL;
	}

	if (opt == NULL)
		opt = np->opt;
	if (flowlabel)
		opt = fl6_merge_options(&opt_space, flowlabel, opt);
	opt = ipv6_fixup_options(&opt_space, opt);

	fl6.flowi6_proto = sk->sk_protocol;
	if (!ipv6_addr_any(daddr))
		fl6.daddr = *daddr;
	else
		fl6.daddr.s6_addr[15] = 0x1; /* :: means loopback (BSD'ism) */
	if (ipv6_addr_any(&fl6.saddr) && !ipv6_addr_any(&np->saddr))
		fl6.saddr = np->saddr;

	final_p = fl6_update_dst(&fl6, opt, &final);

	if (!fl6.flowi6_oif && ipv6_addr_is_multicast(&fl6.daddr))
		fl6.flowi6_oif = np->mcast_oif;
	else if (!fl6.flowi6_oif)
		fl6.flowi6_oif = np->ucast_oif;

	security_sk_classify_flow(sk, flowi6_to_flowi(&fl6));

	dst = ip6_dst_lookup_flow(sk, &fl6, final_p, true);
	if (IS_ERR(dst)) {
		err = PTR_ERR(dst);
		goto out;
	}

	if (hlimit < 0) {
		if (ipv6_addr_is_multicast(&fl6.daddr))
			hlimit = np->mcast_hops;
		else
			hlimit = np->hop_limit;
		if (hlimit < 0)
			hlimit = ip6_dst_hoplimit(dst);
	}

	if (tclass < 0)
		tclass = np->tclass;

	if (dontfrag < 0)
		dontfrag = np->dontfrag;

	if (msg->msg_flags & MSG_CONFIRM)
		goto do_confirm;

back_from_confirm:
	lock_sock(sk);
	err = ip6_append_data(sk, ip_generic_getfrag, msg->msg_iov,
			      ulen, transhdrlen, hlimit, tclass, opt,
			      &fl6, (struct rt6_info *)dst,
			      msg->msg_flags, dontfrag);
	if (err)
		ip6_flush_pending_frames(sk);
	else if (!(msg->msg_flags & MSG_MORE))
		err = l2tp_ip6_push_pending_frames(sk);
	release_sock(sk);
done:
	dst_release(dst);
out:
	fl6_sock_release(flowlabel);

	return err < 0 ? err : len;

do_confirm:
	dst_confirm(dst);
	if (!(msg->msg_flags & MSG_PROBE) || len)
		goto back_from_confirm;
	err = 0;
	goto done;
}