[NETFILTER]: Fix ip_nat_find_helper() locking.

Signed-off-by: Harald Welte <laforge@netfilter.org>
Signed-off-by: David S. Miller <davem@redhat.com>

include/linux/netfilter_ipv4/ip_nat_helper.h

@@ -44,6 +44,9 @@ extern void ip_nat_helper_unregister(struct ip_nat_helper *me);
 extern struct ip_nat_helper *
 ip_nat_find_helper(const struct ip_conntrack_tuple *tuple);
 
+extern struct ip_nat_helper *
+__ip_nat_find_helper(const struct ip_conntrack_tuple *tuple);
+
 /* These return true or false. */
 extern int ip_nat_mangle_tcp_packet(struct sk_buff **skb,
 				struct ip_conntrack *ct,

net/ipv4/netfilter/ip_nat_core.c

@@ -635,7 +635,7 @@ ip_nat_setup_info(struct ip_conntrack *conntrack,
 
 	/* If there's a helper, assign it; based on new tuple. */
 	if (!conntrack->master)
-		info->helper = ip_nat_find_helper(&reply);
+		info->helper = __ip_nat_find_helper(&reply);
 
 	/* It's done. */
 	info->initialized |= (1 << HOOK2MANIP(hooknum));

net/ipv4/netfilter/ip_nat_helper.c

@@ -420,13 +420,19 @@ int ip_nat_helper_register(struct ip_nat_helper *me)
 	return ret;
 }
 
+struct ip_nat_helper *
+__ip_nat_find_helper(const struct ip_conntrack_tuple *tuple)
+{
+	return LIST_FIND(&helpers, helper_cmp, struct ip_nat_helper *, tuple);
+}
+
 struct ip_nat_helper *
 ip_nat_find_helper(const struct ip_conntrack_tuple *tuple)
 {
 	struct ip_nat_helper *h;
 
 	READ_LOCK(&ip_nat_lock);
-	h = LIST_FIND(&helpers, helper_cmp, struct ip_nat_helper *, tuple);
+	h = __ip_nat_find_helper(tuple);
 	READ_UNLOCK(&ip_nat_lock);
 
 	return h;

net/ipv4/netfilter/ip_nat_standalone.c

@@ -394,4 +394,6 @@ EXPORT_SYMBOL(ip_nat_cheat_check);
 EXPORT_SYMBOL(ip_nat_mangle_tcp_packet);
 EXPORT_SYMBOL(ip_nat_mangle_udp_packet);
 EXPORT_SYMBOL(ip_nat_used_tuple);
+EXPORT_SYMBOL(ip_nat_find_helper);
+EXPORT_SYMBOL(__ip_nat_find_helper);
 MODULE_LICENSE("GPL");