netfilter: remove invalid rcu_dereference() calls

The CONFIG_PROVE_RCU option discovered a few invalid uses of
rcu_dereference() in netfilter. In all these cases, the code code
intends to check whether a pointer is already assigned when
performing registration or whether the assigned pointer matches
when performing unregistration. The entire registration/
unregistration is protected by a mutex, so we don't need the
rcu_dereference() calls.

Reported-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Tested-by: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 4 insertions, 14 deletions

diff --git a/net/netfilter/nf_conntrack_ecache.c b/net/netfilter/nf_conntrack_ecache.c
index d5a9bcd7d61..849614af232 100644
--- a/net/netfilter/nf_conntrack_ecache.c
+++ b/net/netfilter/nf_conntrack_ecache.c
@@ -81,11 +81,9 @@ EXPORT_SYMBOL_GPL(nf_ct_deliver_cached_events);
 int nf_conntrack_register_notifier(struct nf_ct_event_notifier *new)
 {
 	int ret = 0;
-	struct nf_ct_event_notifier *notify;
 
 	mutex_lock(&nf_ct_ecache_mutex);
-	notify = rcu_dereference(nf_conntrack_event_cb);
-	if (notify != NULL) {
+	if (nf_conntrack_event_cb != NULL) {
 		ret = -EBUSY;
 		goto out_unlock;
 	}
@@ -101,11 +99,8 @@ EXPORT_SYMBOL_GPL(nf_conntrack_register_notifier);
 
 void nf_conntrack_unregister_notifier(struct nf_ct_event_notifier *new)
 {
-	struct nf_ct_event_notifier *notify;
-
 	mutex_lock(&nf_ct_ecache_mutex);
-	notify = rcu_dereference(nf_conntrack_event_cb);
-	BUG_ON(notify != new);
+	BUG_ON(nf_conntrack_event_cb != new);
 	rcu_assign_pointer(nf_conntrack_event_cb, NULL);
 	mutex_unlock(&nf_ct_ecache_mutex);
 }
@@ -114,11 +109,9 @@ EXPORT_SYMBOL_GPL(nf_conntrack_unregister_notifier);
 int nf_ct_expect_register_notifier(struct nf_exp_event_notifier *new)
 {
 	int ret = 0;
-	struct nf_exp_event_notifier *notify;
 
 	mutex_lock(&nf_ct_ecache_mutex);
-	notify = rcu_dereference(nf_expect_event_cb);
-	if (notify != NULL) {
+	if (nf_expect_event_cb != NULL) {
 		ret = -EBUSY;
 		goto out_unlock;
 	}
@@ -134,11 +127,8 @@ EXPORT_SYMBOL_GPL(nf_ct_expect_register_notifier);
 
 void nf_ct_expect_unregister_notifier(struct nf_exp_event_notifier *new)
 {
-	struct nf_exp_event_notifier *notify;
-
 	mutex_lock(&nf_ct_ecache_mutex);
-	notify = rcu_dereference(nf_expect_event_cb);
-	BUG_ON(notify != new);
+	BUG_ON(nf_expect_event_cb != new);
 	rcu_assign_pointer(nf_expect_event_cb, NULL);
 	mutex_unlock(&nf_ct_ecache_mutex);
 }