netfilter: invoke synchronize_rcu after set the _hook_ to NULL

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@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/ipv4/netfilter/nf_nat_snmp_basic.c b/net/ipv4/netfilter/nf_nat_snmp_basic.c
index c9b52c361da2e6acc746c2de86d8c7f3af0a9b39..5a8f7c360887a73b1558022c83e8433190f0f97d 100644 (file)
--- 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 da9df2d56e669ed33d8126a484788e600dcaaabd..22fc32143e9c4ae17bc48edc68eb0decf11d931c 100644 (file)
--- 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 6806b5e73567bb0220b248682abed3e5e34f780e..908d858034e4f413b13d9965f41c94efd331489a 100644 (file)
--- 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 94b14c5a8b177277e218790da32eafebff3be963..82802e4a6640817e64eb3f3a6ffcb875ad14a747 100644 (file)
--- 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 139e0867e56e9e606942c98e75148eb17b2ec7eb..47d6656c9119fd5c75fb1fb5f0bfd4bb49f1c38b 100644 (file)
--- 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);