linux-kernel - Re: BUG: IPv4: Attempt to release TCP socket in state 1

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Date:	Sat, 16 Mar 2013 10:36:06 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	dormando <dormando@...ia.net>
Cc:	Cong Wang <xiyou.wangcong@...il.com>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: BUG: IPv4: Attempt to release TCP socket in state 1

On Fri, 2013-03-15 at 00:19 +0100, Eric Dumazet wrote:

> Thanks thats really useful, we might miss to increment socket refcount
> in a timer setup.
> 

Hmm, please add following debugging patch as well

diff --git a/include/net/sock.h b/include/net/sock.h
index 14f6e9d..fe7c8a6 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -530,7 +530,9 @@ static inline void sock_hold(struct sock *sk)
  */
 static inline void __sock_put(struct sock *sk)
 {
-	atomic_dec(&sk->sk_refcnt);
+	int newref = atomic_dec_return(&sk->sk_refcnt);
+
+	BUG_ON(newref <= 0);
 }
 
 static inline bool sk_del_node_init(struct sock *sk)
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 786d97a..a445e15 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -739,7 +739,7 @@ void inet_csk_prepare_forced_close(struct sock *sk)
 {
 	/* sk_clone_lock locked the socket and set refcnt to 2 */
 	bh_unlock_sock(sk);
-	sock_put(sk);
+	__sock_put(sk);
 
 	/* The below has to be done to allow calling inet_csk_destroy_sock */
 	sock_set_flag(sk, SOCK_DEAD);
@@ -835,13 +835,13 @@ void inet_csk_listen_stop(struct sock *sk)
 			 * tcp_v4_destroy_sock().
 			 */
 			tcp_sk(child)->fastopen_rsk = NULL;
-			sock_put(sk);
+			__sock_put(sk);
 		}
 		inet_csk_destroy_sock(child);
 
 		bh_unlock_sock(child);
 		local_bh_enable();
-		sock_put(child);
+		__sock_put(child);
 
 		sk_acceptq_removed(sk);
 		__reqsk_free(req);


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