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>

4 files changed, 28 insertions, 13 deletions

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index 8fed1cd78658..f11ca837361b 100644
--- 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
index 37874e2f30ed..ccf40550c475 100644
--- 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 @@ ipv4_connected:
 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
index 982f6c44ea01..1f57094d3111 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -308,21 +308,24 @@ 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);
@@ -330,7 +333,9 @@ static int l2tp_ip_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len
         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
index 9978d01ba0ba..af9abfff637c 100644
--- 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;
 
@@ -390,10 +387,18 @@ 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);
@@ -401,6 +406,7 @@ static int l2tp_ip6_connect(struct sock *sk, struct sockaddr *uaddr,
         sk_add_bind_node(sk, &l2tp_ip6_bind_table);
         write_unlock_bh(&l2tp_ip6_lock);
 
+out_sk:
         release_sock(sk);
 
         return rc;