From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Emelyanov Subject: [PATCH][NETFILTER]: Fix race between clusterip_config_find_get and _entry_put. Date: Sat, 12 Apr 2008 14:44:18 +0400 Message-ID: <48009282.9040808@openvz.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Linux Netdev List , David Miller To: Patrick McHardy Return-path: Received: from sacred.ru ([62.205.161.221]:39656 "EHLO sacred.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757524AbYDLKpY (ORCPT ); Sat, 12 Apr 2008 06:45:24 -0400 Sender: netdev-owner@vger.kernel.org List-ID: Consider we are putting a clusterip_config entry with the "entries" count == 1, and on the other CPU there's a clusterip_config_find_get in progress: CPU1: CPU2: clusterip_config_entry_put: clusterip_config_find_get: if (atomic_dec_and_test(&c->entries)) { /* true */ read_lock_bh(&clusterip_lock); c = __clusterip_config_find(clusterip); /* found - it's still in list */ ... atomic_inc(&c->entries); read_unlock_bh(&clusterip_lock); write_lock_bh(&clusterip_lock); list_del(&c->list); write_unlock_bh(&clusterip_lock); ... dev_put(c->dev); Oops! We have an entry returned by the clusterip_config_find_get, which is a) not in list b) has a stale dev pointer. The problems will happen when the CPU2 will release the entry - it will remove it from the list for the 2nd time, thus spoiling it, and will put a stale dev pointer. The fix is to make atomic_dec_and_test under the clusterip_lock. Signed-off-by: Pavel Emelyanov --- diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c index 52926c8..a12dd32 100644 --- a/net/ipv4/netfilter/ipt_CLUSTERIP.c +++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c @@ -82,8 +82,8 @@ clusterip_config_put(struct clusterip_config *c) static inline void clusterip_config_entry_put(struct clusterip_config *c) { + write_lock_bh(&clusterip_lock); if (atomic_dec_and_test(&c->entries)) { - write_lock_bh(&clusterip_lock); list_del(&c->list); write_unlock_bh(&clusterip_lock); @@ -96,7 +96,9 @@ clusterip_config_entry_put(struct clusterip_config *c) #ifdef CONFIG_PROC_FS remove_proc_entry(c->pde->name, c->pde->parent); #endif + return; } + write_unlock_bh(&clusterip_lock); } static struct clusterip_config *