From d696f0acb09c8a10210532fc7a5e6bd84342e8c3 Mon Sep 17 00:00:00 2001 From: Liping Zhang Date: Sat, 25 Mar 2017 08:53:12 +0800 Subject: [PATCH] netfilter: invoke synchronize_rcu after set the _hook_ to NULL commit 3b7dabf029478bb80507a6c4500ca94132a2bc0b upstream. 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 Signed-off-by: Willy Tarreau --- 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 | 1 + 5 files changed, 7 insertions(+) diff --git a/net/ipv4/netfilter/nf_nat_snmp_basic.c b/net/ipv4/netfilter/nf_nat_snmp_basic.c index 5f011cc89cd9..1e82bdb0f07e 100644 --- a/net/ipv4/netfilter/nf_nat_snmp_basic.c +++ b/net/ipv4/netfilter/nf_nat_snmp_basic.c @@ -1305,6 +1305,7 @@ 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 1df176146567..c9f131fc4bf3 100644 --- a/net/netfilter/nf_conntrack_ecache.c +++ b/net/netfilter/nf_conntrack_ecache.c @@ -116,6 +116,7 @@ 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); @@ -152,6 +153,7 @@ 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 c5621b5e3f86..6208b7f05722 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -3137,6 +3137,7 @@ static void __exit ctnetlink_exit(void) #ifdef CONFIG_NETFILTER_NETLINK_QUEUE_CT RCU_INIT_POINTER(nfq_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 2bb801e3ee8c..7658d0181050 100644 --- a/net/netfilter/nf_nat_core.c +++ b/net/netfilter/nf_nat_core.c @@ -853,6 +853,8 @@ 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]); synchronize_net(); diff --git a/net/netfilter/nfnetlink_cttimeout.c b/net/netfilter/nfnetlink_cttimeout.c index 65074dfb9383..10d78dc0d2c6 100644 --- a/net/netfilter/nfnetlink_cttimeout.c +++ b/net/netfilter/nfnetlink_cttimeout.c @@ -431,6 +431,7 @@ 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 */ }