From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:33128 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933957AbeCMPfV (ORCPT ); Tue, 13 Mar 2018 11:35:21 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+03218bcdba6aa76441a3@syzkaller.appspotmail.com, Paolo Abeni , Xin Long , Pablo Neira Ayuso , Cong Wang Subject: [PATCH 4.14 010/140] netfilter: ipt_CLUSTERIP: fix a race condition of proc file creation Date: Tue, 13 Mar 2018 16:23:33 +0100 Message-Id: <20180313152458.810866282@linuxfoundation.org> In-Reply-To: <20180313152458.201155692@linuxfoundation.org> References: <20180313152458.201155692@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Cong Wang commit b3e456fce9f51d6276e576d00271e2813c1b8b67 upstream. 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 Reviewed-by: Xin Long Signed-off-by: Pablo Neira Ayuso Signed-off-by: Greg Kroah-Hartman --- net/ipv4/netfilter/ipt_CLUSTERIP.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) --- a/net/ipv4/netfilter/ipt_CLUSTERIP.c +++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c @@ -107,12 +107,6 @@ clusterip_config_entry_put(struct net *n 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 *n 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();