[NETFILTER]: nf_nat: properly use RCU for ip_nat_decode_session

We need to use rcu_assign_pointer/rcu_dereference to avoid races.
Also remove an obsolete CONFIG_IP_NAT_NEEDED ifdef.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 11 insertions, 6 deletions

diff --git a/include/linux/netfilter.h b/include/linux/netfilter.h
index 0947424d01d6..1a8487325a4f 100644
--- a/include/linux/netfilter.h
+++ b/include/linux/netfilter.h
@@ -256,11 +256,16 @@ extern void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
 static inline void
 nf_nat_decode_session(struct sk_buff *skb, struct flowi *fl, int family)
 {
-#if defined(CONFIG_IP_NF_NAT_NEEDED) || defined(CONFIG_NF_NAT_NEEDED)
+#ifdef CONFIG_NF_NAT_NEEDED
         void (*decodefn)(struct sk_buff *, struct flowi *);
 
-        if (family == AF_INET && (decodefn = ip_nat_decode_session) != NULL)
-                decodefn(skb, fl);
+        if (family == AF_INET) {
+                rcu_read_lock();
+                decodefn = rcu_dereference(ip_nat_decode_session);
+                if (decodefn)
+                        decodefn(skb, fl);
+                rcu_read_unlock();
+        }
 #endif
 }
 
diff --git a/net/ipv4/netfilter/nf_nat_standalone.c b/net/ipv4/netfilter/nf_nat_standalone.c
index a2b02f01cc5c..99b2c788d5a8 100644
--- a/net/ipv4/netfilter/nf_nat_standalone.c
+++ b/net/ipv4/netfilter/nf_nat_standalone.c
@@ -332,7 +332,7 @@ static int __init nf_nat_standalone_init(void)
 
 #ifdef CONFIG_XFRM
         BUG_ON(ip_nat_decode_session != NULL);
-        ip_nat_decode_session = nat_decode_session;
+        rcu_assign_pointer(ip_nat_decode_session, nat_decode_session);
 #endif
         ret = nf_nat_rule_init();
         if (ret < 0) {
@@ -350,7 +350,7 @@ static int __init nf_nat_standalone_init(void)
         nf_nat_rule_cleanup();
  cleanup_decode_session:
 #ifdef CONFIG_XFRM
-        ip_nat_decode_session = NULL;
+        rcu_assign_pointer(ip_nat_decode_session, NULL);
         synchronize_net();
 #endif
         return ret;
@@ -361,7 +361,7 @@ static void __exit nf_nat_standalone_fini(void)
         nf_unregister_hooks(nf_nat_ops, ARRAY_SIZE(nf_nat_ops));
         nf_nat_rule_cleanup();
 #ifdef CONFIG_XFRM
-        ip_nat_decode_session = NULL;
+        rcu_assign_pointer(ip_nat_decode_session, NULL);
         synchronize_net();
 #endif
         /* Conntrack caches are unregistered in nf_conntrack_cleanup */