tcp: Fix a connect() race with timewait sockets

First patch changes __inet_hash_nolisten() and __inet6_hash()
to get a timewait parameter to be able to unhash it from ehash
at same time the new socket is inserted in hash.

This makes sure timewait socket wont be found by a concurrent
writer in __inet_check_established()

Reported-by: kapil dakhane <kdakhane@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 9 insertions, 3 deletions

diff --git a/net/ipv6/inet6_hashtables.c b/net/ipv6/inet6_hashtables.c
index c813e294ec0c..633a6c266136 100644
--- a/net/ipv6/inet6_hashtables.c
+++ b/net/ipv6/inet6_hashtables.c
@@ -22,9 +22,10 @@
 #include <net/inet6_hashtables.h>
 #include <net/ip.h>
 
-void __inet6_hash(struct sock *sk)
+int __inet6_hash(struct sock *sk, struct inet_timewait_sock *tw)
 {
         struct inet_hashinfo *hashinfo = sk->sk_prot->h.hashinfo;
+        int twrefcnt = 0;
 
         WARN_ON(!sk_unhashed(sk));
 
@@ -45,10 +46,15 @@ void __inet6_hash(struct sock *sk)
                 lock = inet_ehash_lockp(hashinfo, hash);
                 spin_lock(lock);
                 __sk_nulls_add_node_rcu(sk, list);
+                if (tw) {
+                        WARN_ON(sk->sk_hash != tw->tw_hash);
+                        twrefcnt = inet_twsk_unhash(tw);
+                }
                 spin_unlock(lock);
         }
 
         sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
+        return twrefcnt;
 }
 EXPORT_SYMBOL(__inet6_hash);
 
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index aadd7cef73b3..ee9cf62458d4 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -96,7 +96,7 @@ static void tcp_v6_hash(struct sock *sk)
                         return;
                 }
                 local_bh_disable();
-                __inet6_hash(sk);
+                __inet6_hash(sk, NULL);
                 local_bh_enable();
         }
 }
@@ -1496,7 +1496,7 @@ static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
         }
 #endif
 
-        __inet6_hash(newsk);
+        __inet6_hash(newsk, NULL);
         __inet_inherit_port(sk, newsk);
 
         return newsk;