[NETFILTER]: ip_conntrack: properly use RCU for ip_conntrack_destroyed callback

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

net/ipv4/netfilter/ip_conntrack_core.c

@@ -303,6 +303,7 @@ destroy_conntrack(struct nf_conntrack *nfct)
 	struct ip_conntrack *ct = (struct ip_conntrack *)nfct;
 	struct ip_conntrack_protocol *proto;
 	struct ip_conntrack_helper *helper;
+	typeof(ip_conntrack_destroyed) destroyed;
 
 	DEBUGP("destroy_conntrack(%p)\n", ct);
 	IP_NF_ASSERT(atomic_read(&nfct->use) == 0);
@@ -322,10 +323,12 @@ destroy_conntrack(struct nf_conntrack *nfct)
 	proto = __ip_conntrack_proto_find(ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.protonum);
 	if (proto && proto->destroy)
 		proto->destroy(ct);
-	rcu_read_unlock();
 
-	if (ip_conntrack_destroyed)
-		ip_conntrack_destroyed(ct);
+	destroyed = rcu_dereference(ip_conntrack_destroyed);
+	if (destroyed)
+		destroyed(ct);
+
+	rcu_read_unlock();
 
 	write_lock_bh(&ip_conntrack_lock);
 	/* Expectations will have been removed in clean_from_lists,

net/ipv4/netfilter/ip_nat_core.c

@@ -604,8 +604,8 @@ static int __init ip_nat_init(void)
 	}
 
 	/* FIXME: Man, this is a hack.  <SIGH> */
-	IP_NF_ASSERT(ip_conntrack_destroyed == NULL);
-	ip_conntrack_destroyed = &ip_nat_cleanup_conntrack;
+	IP_NF_ASSERT(rcu_dereference(ip_conntrack_destroyed) == NULL);
+	rcu_assign_pointer(ip_conntrack_destroyed, ip_nat_cleanup_conntrack);
 
 	/* Initialize fake conntrack so that NAT will skip it */
 	ip_conntrack_untracked.status |= IPS_NAT_DONE_MASK;
@@ -623,7 +623,8 @@ static int clean_nat(struct ip_conntrack *i, void *data)
 static void __exit ip_nat_cleanup(void)
 {
 	ip_ct_iterate_cleanup(&clean_nat, NULL);
-	ip_conntrack_destroyed = NULL;
+	rcu_assign_pointer(ip_conntrack_destroyed, NULL);
+	synchronize_rcu();
 	vfree(bysource);
 }