From ac57b3a9ce280763296f99e32187a0b4384d9389 Mon Sep 17 00:00:00 2001 From: Denis Lunev Date: Wed, 18 Apr 2007 17:05:58 -0700 Subject: [PATCH] [NETLINK]: Don't attach callback to a going-away netlink socket 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. Here it is: CPU1: CPU2 netlink_release(): netlink_dump_start(): sk = netlink_lookup(); /* OK */ netlink_remove(); spin_lock(&nlk->cb_lock); if (nlk->cb) { /* false */ ... } spin_unlock(&nlk->cb_lock); spin_lock(&nlk->cb_lock); if (nlk->cb) { /* false */ ... } nlk->cb = cb; spin_unlock(&nlk->cb_lock); ... sock_orphan(sk); /* * proceed with releasing * the socket */ The proposal it to make sock_orphan before detaching the callback in netlink_release() and to check for the sock to be SOCK_DEAD in netlink_dump_start() before setting a new callback. Signed-off-by: Denis Lunev Signed-off-by: Kirill Korotaev Signed-off-by: Pavel Emelianov Acked-by: Patrick McHardy Signed-off-by: David S. Miller --- net/netlink/af_netlink.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index e73d8f546c6..c48b0f49f00 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -443,6 +443,7 @@ static int netlink_release(struct socket *sock) return 0; netlink_remove(sk); + sock_orphan(sk); nlk = nlk_sk(sk); spin_lock(&nlk->cb_lock); @@ -457,7 +458,6 @@ static int netlink_release(struct socket *sock) /* OK. Socket is unlinked, and, therefore, no new packets will arrive */ - sock_orphan(sk); sock->sk = NULL; wake_up_interruptible_all(&nlk->wait); @@ -1412,9 +1412,9 @@ int netlink_dump_start(struct sock *ssk, struct sk_buff *skb, 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); -- 2.41.0