From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: [PATCH 4/8] netfilter: invoke synchronize_rcu after set the _hook_ to NULL Date: Wed, 29 Mar 2017 14:14:06 +0200 Message-ID: <1490789650-7294-5-git-send-email-pablo@netfilter.org> References: <1490789650-7294-1-git-send-email-pablo@netfilter.org> Cc: davem@davemloft.net, netdev@vger.kernel.org To: netfilter-devel@vger.kernel.org Return-path: Received: from mail.us.es ([193.147.175.20]:43442 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756063AbdC2MPG (ORCPT ); Wed, 29 Mar 2017 08:15:06 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id 49291EBAC3 for ; Wed, 29 Mar 2017 14:15:02 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 3812CDA804 for ; Wed, 29 Mar 2017 14:15:02 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id 09882DA865 for ; Wed, 29 Mar 2017 14:15:00 +0200 (CEST) In-Reply-To: <1490789650-7294-1-git-send-email-pablo@netfilter.org> Sender: netdev-owner@vger.kernel.org List-ID: From: Liping Zhang Otherwise, another CPU may access the invalid pointer. For example: CPU0 CPU1 - rcu_read_lock(); - pfunc = _hook_; _hook_ = NULL; - mod unload - - pfunc(); // invalid, panic - rcu_read_unlock(); So we must call synchronize_rcu() to wait the rcu reader to finish. Also note, in nf_nat_snmp_basic_fini, synchronize_rcu() will be invoked by later nf_conntrack_helper_unregister, but I'm inclined to add a explicit synchronize_rcu after set the nf_nat_snmp_hook to NULL. Depend on such obscure assumptions is not a good idea. Last, in nfnetlink_cttimeout, we use kfree_rcu to free the time object, so in cttimeout_exit, invoking rcu_barrier() is not necessary at all, remove it too. Signed-off-by: Liping Zhang Signed-off-by: Pablo Neira Ayuso --- net/ipv4/netfilter/nf_nat_snmp_basic.c | 1 + net/netfilter/nf_conntrack_ecache.c | 2 ++ net/netfilter/nf_conntrack_netlink.c | 1 + net/netfilter/nf_nat_core.c | 2 ++ net/netfilter/nfnetlink_cttimeout.c | 2 +- 5 files changed, 7 insertions(+), 1 deletion(-) diff --git a/net/ipv4/netfilter/nf_nat_snmp_basic.c b/net/ipv4/netfilter/nf_nat_snmp_basic.c index c9b52c361da2..5a8f7c360887 100644 --- a/net/ipv4/netfilter/nf_nat_snmp_basic.c +++ b/net/ipv4/netfilter/nf_nat_snmp_basic.c @@ -1304,6 +1304,7 @@ static int __init nf_nat_snmp_basic_init(void) static void __exit nf_nat_snmp_basic_fini(void) { RCU_INIT_POINTER(nf_nat_snmp_hook, NULL); + synchronize_rcu(); nf_conntrack_helper_unregister(&snmp_trap_helper); } diff --git a/net/netfilter/nf_conntrack_ecache.c b/net/netfilter/nf_conntrack_ecache.c index da9df2d56e66..22fc32143e9c 100644 --- a/net/netfilter/nf_conntrack_ecache.c +++ b/net/netfilter/nf_conntrack_ecache.c @@ -290,6 +290,7 @@ void nf_conntrack_unregister_notifier(struct net *net, BUG_ON(notify != new); RCU_INIT_POINTER(net->ct.nf_conntrack_event_cb, NULL); mutex_unlock(&nf_ct_ecache_mutex); + /* synchronize_rcu() is called from ctnetlink_exit. */ } EXPORT_SYMBOL_GPL(nf_conntrack_unregister_notifier); @@ -326,6 +327,7 @@ void nf_ct_expect_unregister_notifier(struct net *net, BUG_ON(notify != new); RCU_INIT_POINTER(net->ct.nf_expect_event_cb, NULL); mutex_unlock(&nf_ct_ecache_mutex); + /* synchronize_rcu() is called from ctnetlink_exit. */ } EXPORT_SYMBOL_GPL(nf_ct_expect_unregister_notifier); diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index 6806b5e73567..908d858034e4 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -3442,6 +3442,7 @@ static void __exit ctnetlink_exit(void) #ifdef CONFIG_NETFILTER_NETLINK_GLUE_CT RCU_INIT_POINTER(nfnl_ct_hook, NULL); #endif + synchronize_rcu(); } module_init(ctnetlink_init); diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c index 94b14c5a8b17..82802e4a6640 100644 --- a/net/netfilter/nf_nat_core.c +++ b/net/netfilter/nf_nat_core.c @@ -903,6 +903,8 @@ static void __exit nf_nat_cleanup(void) #ifdef CONFIG_XFRM RCU_INIT_POINTER(nf_nat_decode_session_hook, NULL); #endif + synchronize_rcu(); + for (i = 0; i < NFPROTO_NUMPROTO; i++) kfree(nf_nat_l4protos[i]); diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c index 139e0867e56e..47d6656c9119 100644 --- a/net/netfilter/nfnetlink_cttimeout.c +++ b/net/netfilter/nfnetlink_cttimeout.c @@ -646,8 +646,8 @@ static void __exit cttimeout_exit(void) #ifdef CONFIG_NF_CONNTRACK_TIMEOUT RCU_INIT_POINTER(nf_ct_timeout_find_get_hook, NULL); RCU_INIT_POINTER(nf_ct_timeout_put_hook, NULL); + synchronize_rcu(); #endif /* CONFIG_NF_CONNTRACK_TIMEOUT */ - rcu_barrier(); } module_init(cttimeout_init); -- 2.1.4