Subject: [PATCH] Inet-hashtable: Change the range of sk->hash lock to avoid the race condition.

From: Jun Chen <[email-masked]>
Date: Thu, 12 Sep 2013 12:32:29 -0400

When try to add node to list in __inet_hash_nolisten function, first get the
list and then to lock for using, but in extremeness case, others can del this
node before locking it, then the node should be null.So this patch try to lock
firstly and then get the list for using to avoid this race condition.

Signed-off-by: Chen Jun <[email-masked]>
---
 net/ipv4/inet_hashtables.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 7bd8983..76e846e 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -407,12 +407,15 @@ int __inet_hash_nolisten(struct sock *sk, struct inet_timewait_sock *tw)
 	WARN_ON(!sk_unhashed(sk));
 
 	sk->sk_hash = inet_sk_ehashfn(sk);
-	head = inet_ehash_bucket(hashinfo, sk->sk_hash);
-	list = &head->chain;
 	lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
 
 	spin_lock(lock);
-	__sk_nulls_add_node_rcu(sk, list);
+	if (sk_hashed(sk)) {
+		head = inet_ehash_bucket(hashinfo, sk->sk_hash);
+		list = &head->chain;
+		__sk_nulls_add_node_rcu(sk, list);
+	}
+
 	if (tw) {
 		WARN_ON(sk->sk_hash != tw->tw_hash);
 		twrefcnt = inet_twsk_unhash(tw);
-- 
1.7.4.1