af_unix: Annodate data-races around sk->sk_state for writers.

sk->sk_state is changed under unix_state_lock(), but it's read locklessly
in many places.

This patch adds WRITE_ONCE() on the writer side.

We will add READ_ONCE() to the lockless readers in the following patches.

Fixes: 83301b53 ("af_unix: Set TCP_ESTABLISHED for datagram sockets too")
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/unix/af_unix.c

@@ -616,7 +616,7 @@ static void unix_release_sock(struct sock *sk, int embrion)
 	u->path.dentry = NULL;
 	u->path.mnt = NULL;
 	state = sk->sk_state;
-	sk->sk_state = TCP_CLOSE;
+	WRITE_ONCE(sk->sk_state, TCP_CLOSE);
 
 	skpair = unix_peer(sk);
 	unix_peer(sk) = NULL;
@@ -738,7 +738,8 @@ static int unix_listen(struct socket *sock, int backlog)
 	if (backlog > sk->sk_max_ack_backlog)
 		wake_up_interruptible_all(&u->peer_wait);
 	sk->sk_max_ack_backlog	= backlog;
-	sk->sk_state		= TCP_LISTEN;
+	WRITE_ONCE(sk->sk_state, TCP_LISTEN);
+
 	/* set credentials so connect can copy them */
 	init_peercred(sk);
 	err = 0;
@@ -1401,7 +1402,8 @@ static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
 		if (err)
 			goto out_unlock;
 
-		sk->sk_state = other->sk_state = TCP_ESTABLISHED;
+		WRITE_ONCE(sk->sk_state, TCP_ESTABLISHED);
+		WRITE_ONCE(other->sk_state, TCP_ESTABLISHED);
 	} else {
 		/*
 		 *	1003.1g breaking connected state with AF_UNSPEC
@@ -1418,7 +1420,7 @@ static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
 
 		unix_peer(sk) = other;
 		if (!other)
-			sk->sk_state = TCP_CLOSE;
+			WRITE_ONCE(sk->sk_state, TCP_CLOSE);
 		unix_dgram_peer_wake_disconnect_wakeup(sk, old_peer);
 
 		unix_state_double_unlock(sk, other);
@@ -1639,7 +1641,7 @@ static int unix_stream_connect(struct socket *sock, struct sockaddr *uaddr,
 	copy_peercred(sk, other);
 
 	sock->state	= SS_CONNECTED;
-	sk->sk_state	= TCP_ESTABLISHED;
+	WRITE_ONCE(sk->sk_state, TCP_ESTABLISHED);
 	sock_hold(newsk);
 
 	smp_mb__after_atomic();	/* sock_hold() does an atomic_inc() */
@@ -2050,7 +2052,7 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
 			unix_peer(sk) = NULL;
 			unix_dgram_peer_wake_disconnect_wakeup(sk, other);
 
-			sk->sk_state = TCP_CLOSE;
+			WRITE_ONCE(sk->sk_state, TCP_CLOSE);
 			unix_state_unlock(sk);
 
 			unix_dgram_disconnected(sk, other);