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Date: Mon, 18 Sep 2017 00:19:40 +0000 From: "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com> To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "stable@...r.kernel.org" <stable@...r.kernel.org> Cc: Liping Zhang <zlpnobody@...il.com>, Pablo Neira Ayuso <pablo@...filter.org>, "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com> Subject: [PATCH for 4.9 16/39] netfilter: invoke synchronize_rcu after set the _hook_ to NULL From: Liping Zhang <zlpnobody@...il.com> [ Upstream commit 3b7dabf029478bb80507a6c4500ca94132a2bc0b ] 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 <zlpnobody@...il.com> Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org> Signed-off-by: Sasha Levin <alexander.levin@...izon.com> --- 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 04111c1c3988..d5caed5bcfb1 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -3413,6 +3413,7 @@ 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 dde64c4565d2..2916f4815c9c 100644 --- a/net/netfilter/nf_nat_core.c +++ b/net/netfilter/nf_nat_core.c @@ -892,6 +892,8 @@ 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); -- 2.11.0
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