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>

2 files changed, 6 insertions, 20 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);
 }
diff --git a/net/netfilter/nf_log.c b/net/netfilter/nf_log.c
index 015725a5cd5..908f59935fb 100644
--- a/net/netfilter/nf_log.c
+++ b/net/netfilter/nf_log.c
@@ -35,7 +35,6 @@ static struct nf_logger *__find_logger(int pf, const char *str_logger)
 /* return EEXIST if the same logger is registred, 0 on success. */
 int nf_log_register(u_int8_t pf, struct nf_logger *logger)
 {
-        const struct nf_logger *llog;
         int i;
 
         if (pf >= ARRAY_SIZE(nf_loggers))
@@ -52,8 +51,7 @@ int nf_log_register(u_int8_t pf, struct nf_logger *logger)
         } else {
                 /* register at end of list to honor first register win */
                 list_add_tail(&logger->list[pf], &nf_loggers_l[pf]);
-                llog = rcu_dereference(nf_loggers[pf]);
-                if (llog == NULL)
+                if (nf_loggers[pf] == NULL)
                         rcu_assign_pointer(nf_loggers[pf], logger);
         }
 
@@ -65,13 +63,11 @@ EXPORT_SYMBOL(nf_log_register);
 
 void nf_log_unregister(struct nf_logger *logger)
 {
-        const struct nf_logger *c_logger;
         int i;
 
         mutex_lock(&nf_log_mutex);
         for (i = 0; i < ARRAY_SIZE(nf_loggers); i++) {
-                c_logger = rcu_dereference(nf_loggers[i]);
-                if (c_logger == logger)
+                if (nf_loggers[i] == logger)
                         rcu_assign_pointer(nf_loggers[i], NULL);
                 list_del(&logger->list[i]);
         }