From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: [Patch net] ipt_CLUSTERIP: fix a race condition of proc file creation Date: Wed, 7 Feb 2018 21:59:17 -0800 Message-ID: <20180208055918.20411-1-xiyou.wangcong@gmail.com> Cc: netfilter-devel@vger.kernel.org, pabeni@redhat.com, Cong Wang , Xin Long , Pablo Neira Ayuso To: netdev@vger.kernel.org Return-path: Received: from mail-pl0-f68.google.com ([209.85.160.68]:36804 "EHLO mail-pl0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807AbeBHF7a (ORCPT ); Thu, 8 Feb 2018 00:59:30 -0500 Sender: netdev-owner@vger.kernel.org List-ID: There is a race condition between clusterip_config_entry_put() and clusterip_config_init(), after we release the spinlock in clusterip_config_entry_put(), a new proc file with a same IP could be created immediately since it is already removed from the configs list, therefore it triggers this warning: ------------[ cut here ]------------ proc_dir_entry 'ipt_CLUSTERIP/172.20.0.170' already registered WARNING: CPU: 1 PID: 4152 at fs/proc/generic.c:330 proc_register+0x2a4/0x370 fs/proc/generic.c:329 Kernel panic - not syncing: panic_on_warn set ... As a quick fix, just move the proc_remove() inside the spinlock. Reported-by: Fixes: 6c5d5cfbe3c5 ("netfilter: ipt_CLUSTERIP: check duplicate config when initializing") Tested-by: Paolo Abeni Cc: Xin Long Cc: Pablo Neira Ayuso Signed-off-by: Cong Wang --- net/ipv4/netfilter/ipt_CLUSTERIP.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c index 3a84a60f6b39..1ff72b87a066 100644 --- a/net/ipv4/netfilter/ipt_CLUSTERIP.c +++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c @@ -107,12 +107,6 @@ clusterip_config_entry_put(struct net *net, struct clusterip_config *c) local_bh_disable(); if (refcount_dec_and_lock(&c->entries, &cn->lock)) { - list_del_rcu(&c->list); - spin_unlock(&cn->lock); - local_bh_enable(); - - unregister_netdevice_notifier(&c->notifier); - /* In case anyone still accesses the file, the open/close * functions are also incrementing the refcount on their own, * so it's safe to remove the entry even if it's in use. */ @@ -120,6 +114,12 @@ clusterip_config_entry_put(struct net *net, struct clusterip_config *c) if (cn->procdir) proc_remove(c->pde); #endif + list_del_rcu(&c->list); + spin_unlock(&cn->lock); + local_bh_enable(); + + unregister_netdevice_notifier(&c->notifier); + return; } local_bh_enable(); -- 2.13.0