[PATCH] Don't attach callback to a going-away netlink socket

[Pavel Emelianov <xemul@sw.ru>]

From: Denis Lunev <den@openvz.org>

There is a race between netlink_dump_start() and netlink_release()
that can lead to the situation when a netlink socket with non-zero
callback is freed.

--- a/net/netlink/af_netlink.c	2004-10-25 12:12:23.000000000 +0400
+++ b/net/netlink/af_netlink.c	2004-10-28 16:26:12.000000000 +0400
@@ -255,6 +255,7 @@ static int netlink_release(struct socket
 		return 0;
 
 	netlink_remove(sk);
+	sock_orphan(sk);
 	nlk = nlk_sk(sk);
 
 	spin_lock(&nlk->cb_lock);
@@ -269,7 +270,6 @@ static int netlink_release(struct socket
 	/* OK. Socket is unlinked, and, therefore,
 	   no new packets will arrive */
 
-	sock_orphan(sk);
 	sock->sk = NULL;
 	wake_up_interruptible_all(&nlk->wait);
 
@@ -942,9 +942,9 @@ int netlink_dump_start(struct sock *ssk,
 		return -ECONNREFUSED;
 	}
 	nlk = nlk_sk(sk);
-	/* A dump is in progress... */
+	/* A dump or destruction is in progress... */
 	spin_lock(&nlk->cb_lock);
-	if (nlk->cb) {
+	if (nlk->cb || sock_flag(sk, SOCK_DEAD)) {
 		spin_unlock(&nlk->cb_lock);
 		netlink_destroy_callback(cb);
 		sock_put(sk);