l2tp: lock socket before checking flags in connect()

Socket flags aren't updated atomically, so the socket must be locked while reading the SOCK_ZAPPED flag. This issue exists for both l2tp_ip and l2tp_ip6. For IPv6, this patch also brings error handling for __ip6_datagram_connect() failures. Signed-off-by: Guillaume Nault <g.nault@alphalink.fr> Signed-off-by: David S. Miller <davem@davemloft.net>
mariux64 · Nov 30, 2016 · 0382a25 · 0382a25
1 parent bb83d62
commit 0382a25
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Showing 4 changed files with 28 additions and 13 deletions.
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
@@ -970,6 +970,8 @@ int compat_ipv6_setsockopt(struct sock *sk, int level, int optname,
 int compat_ipv6_getsockopt(struct sock *sk, int level, int optname,
 			   char __user *optval, int __user *optlen);
 
+int __ip6_datagram_connect(struct sock *sk, struct sockaddr *addr,
+			   int addr_len);
 int ip6_datagram_connect(struct sock *sk, struct sockaddr *addr, int addr_len);
 int ip6_datagram_connect_v6_only(struct sock *sk, struct sockaddr *addr,
 				 int addr_len);

diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
@@ -139,7 +139,8 @@ void ip6_datagram_release_cb(struct sock *sk)
 }
 EXPORT_SYMBOL_GPL(ip6_datagram_release_cb);
 
-static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr,
+			   int addr_len)
 {
 	struct sockaddr_in6	*usin = (struct sockaddr_in6 *) uaddr;
 	struct inet_sock	*inet = inet_sk(sk);
@@ -252,6 +253,7 @@ static int __ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int a
 out:
 	return err;
 }
+EXPORT_SYMBOL_GPL(__ip6_datagram_connect);
 
 int ip6_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
 {

diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
@@ -308,29 +308,34 @@ static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
 	struct sockaddr_l2tpip *lsa = (struct sockaddr_l2tpip *) uaddr;
 	int rc;
 
-	if (sock_flag(sk, SOCK_ZAPPED)) /* Must bind first - autobinding does not work */
-		return -EINVAL;
-
 	if (addr_len < sizeof(*lsa))
 		return -EINVAL;
 
 	if (ipv4_is_multicast(lsa->l2tp_addr.s_addr))
 		return -EINVAL;
 
-	rc = ip4_datagram_connect(sk, uaddr, addr_len);
-	if (rc < 0)
-		return rc;
-
 	lock_sock(sk);
 
+	/* Must bind first - autobinding does not work */
+	if (sock_flag(sk, SOCK_ZAPPED)) {
+		rc = -EINVAL;
+		goto out_sk;
+	}
+
+	rc = __ip4_datagram_connect(sk, uaddr, addr_len);
+	if (rc < 0)
+		goto out_sk;
+
 	l2tp_ip_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;
 
 	write_lock_bh(&l2tp_ip_lock);
 	hlist_del_init(&sk->sk_bind_node);
 	sk_add_bind_node(sk, &l2tp_ip_bind_table);
 	write_unlock_bh(&l2tp_ip_lock);
 
+out_sk:
 	release_sock(sk);
+
 	return rc;
 }
 

diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
@@ -371,9 +371,6 @@ static int l2tp_ip6_connect(struct sock *sk, struct sockaddr *uaddr,
 	int	addr_type;
 	int rc;
 
-	if (sock_flag(sk, SOCK_ZAPPED)) /* Must bind first - autobinding does not work */
-		return -EINVAL;
-
 	if (addr_len < sizeof(*lsa))
 		return -EINVAL;
 
@@ -390,17 +387,26 @@ static int l2tp_ip6_connect(struct sock *sk, struct sockaddr *uaddr,
 			return -EINVAL;
 	}
 
-	rc = ip6_datagram_connect(sk, uaddr, addr_len);
-
 	lock_sock(sk);
 
+	 /* Must bind first - autobinding does not work */
+	if (sock_flag(sk, SOCK_ZAPPED)) {
+		rc = -EINVAL;
+		goto out_sk;
+	}
+
+	rc = __ip6_datagram_connect(sk, uaddr, addr_len);
+	if (rc < 0)
+		goto out_sk;
+
 	l2tp_ip6_sk(sk)->peer_conn_id = lsa->l2tp_conn_id;
 
 	write_lock_bh(&l2tp_ip6_lock);
 	hlist_del_init(&sk->sk_bind_node);
 	sk_add_bind_node(sk, &l2tp_ip6_bind_table);
 	write_unlock_bh(&l2tp_ip6_lock);
 
+out_sk:
 	release_sock(sk);
 
 	return rc;