netfilter: add missing error handling code for register functions

register_{netdevice/inetaddr/inet6addr}_notifier may return an error
value, this patch adds the code to handle these error paths.

Signed-off-by: Taehee Yoo <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/net/netfilter/ipv4/nf_nat_masquerade.h

···
 		       const struct nf_nat_range2 *range,
 		       const struct net_device *out);
 
-void nf_nat_masquerade_ipv4_register_notifier(void);
+int nf_nat_masquerade_ipv4_register_notifier(void);
 void nf_nat_masquerade_ipv4_unregister_notifier(void);
 
 #endif /*_NF_NAT_MASQUERADE_IPV4_H_ */

include/net/netfilter/ipv6/nf_nat_masquerade.h

···
 unsigned int
 nf_nat_masquerade_ipv6(struct sk_buff *skb, const struct nf_nat_range2 *range,
 		       const struct net_device *out);
-void nf_nat_masquerade_ipv6_register_notifier(void);
+int nf_nat_masquerade_ipv6_register_notifier(void);
 void nf_nat_masquerade_ipv6_unregister_notifier(void);
 
 #endif /* _NF_NAT_MASQUERADE_IPV6_H_ */

net/ipv4/netfilter/ipt_MASQUERADE.c

···
 	int ret;
 
 	ret = xt_register_target(&masquerade_tg_reg);
+	if (ret)
+		return ret;
 
-	if (ret == 0)
-		nf_nat_masquerade_ipv4_register_notifier();
+	ret = nf_nat_masquerade_ipv4_register_notifier();
+	if (ret)
+		xt_unregister_target(&masquerade_tg_reg);
 
 	return ret;
 }

net/ipv4/netfilter/nf_nat_masquerade_ipv4.c

···
 
 static atomic_t masquerade_notifier_refcount = ATOMIC_INIT(0);
 
-void nf_nat_masquerade_ipv4_register_notifier(void)
+int nf_nat_masquerade_ipv4_register_notifier(void)
 {
+	int ret;
+
 	/* check if the notifier was already set */
 	if (atomic_inc_return(&masquerade_notifier_refcount) > 1)
-		return;
+		return 0;
 
 	/* Register for device down reports */
-	register_netdevice_notifier(&masq_dev_notifier);
+	ret = register_netdevice_notifier(&masq_dev_notifier);
+	if (ret)
+		goto err_dec;
 	/* Register IP address change reports */
-	register_inetaddr_notifier(&masq_inet_notifier);
+	ret = register_inetaddr_notifier(&masq_inet_notifier);
+	if (ret)
+		goto err_unregister;
+
+	return ret;
+err_unregister:
+	unregister_netdevice_notifier(&masq_dev_notifier);
+err_dec:
+	atomic_dec(&masquerade_notifier_refcount);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv4_register_notifier);
 

net/ipv4/netfilter/nft_masq_ipv4.c

···
 	if (ret < 0)
 		return ret;
 
-	nf_nat_masquerade_ipv4_register_notifier();
+	ret = nf_nat_masquerade_ipv4_register_notifier();
+	if (ret)
+		nft_unregister_expr(&nft_masq_ipv4_type);
 
 	return ret;
 }

net/ipv6/netfilter/ip6t_MASQUERADE.c

···
 	int err;
 
 	err = xt_register_target(&masquerade_tg6_reg);
-	if (err == 0)
-		nf_nat_masquerade_ipv6_register_notifier();
+	if (err)
+		return err;
+
+	err = nf_nat_masquerade_ipv6_register_notifier();
+	if (err)
+		xt_unregister_target(&masquerade_tg6_reg);
 
 	return err;
 }

net/ipv6/netfilter/nf_nat_masquerade_ipv6.c

···
  * of ipv6 addresses being deleted), we also need to add an upper
  * limit to the number of queued work items.
  */
-static int masq_inet_event(struct notifier_block *this,
-			   unsigned long event, void *ptr)
+static int masq_inet6_event(struct notifier_block *this,
+			    unsigned long event, void *ptr)
 {
 	struct inet6_ifaddr *ifa = ptr;
 	const struct net_device *dev;
···
 	return NOTIFY_DONE;
 }
 
-static struct notifier_block masq_inet_notifier = {
-	.notifier_call	= masq_inet_event,
+static struct notifier_block masq_inet6_notifier = {
+	.notifier_call	= masq_inet6_event,
 };
 
 static atomic_t masquerade_notifier_refcount = ATOMIC_INIT(0);
 
-void nf_nat_masquerade_ipv6_register_notifier(void)
+int nf_nat_masquerade_ipv6_register_notifier(void)
 {
+	int ret;
+
 	/* check if the notifier is already set */
 	if (atomic_inc_return(&masquerade_notifier_refcount) > 1)
-		return;
+		return 0;
 
-	register_netdevice_notifier(&masq_dev_notifier);
-	register_inet6addr_notifier(&masq_inet_notifier);
+	ret = register_netdevice_notifier(&masq_dev_notifier);
+	if (ret)
+		goto err_dec;
+
+	ret = register_inet6addr_notifier(&masq_inet6_notifier);
+	if (ret)
+		goto err_unregister;
+
+	return ret;
+err_unregister:
+	unregister_netdevice_notifier(&masq_dev_notifier);
+err_dec:
+	atomic_dec(&masquerade_notifier_refcount);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6_register_notifier);
 
···
 	if (atomic_dec_return(&masquerade_notifier_refcount) > 0)
 		return;
 
-	unregister_inet6addr_notifier(&masq_inet_notifier);
+	unregister_inet6addr_notifier(&masq_inet6_notifier);
 	unregister_netdevice_notifier(&masq_dev_notifier);
 }
 EXPORT_SYMBOL_GPL(nf_nat_masquerade_ipv6_unregister_notifier);

net/ipv6/netfilter/nft_masq_ipv6.c

···
 	if (ret < 0)
 		return ret;
 
-	nf_nat_masquerade_ipv6_register_notifier();
+	ret = nf_nat_masquerade_ipv6_register_notifier();
+	if (ret)
+		nft_unregister_expr(&nft_masq_ipv6_type);
 
 	return ret;
 }

net/netfilter/nft_flow_offload.c

···
 {
 	int err;
 
-	register_netdevice_notifier(&flow_offload_netdev_notifier);
+	err = register_netdevice_notifier(&flow_offload_netdev_notifier);
+	if (err)
+		goto err;
 
 	err = nft_register_expr(&nft_flow_offload_type);
 	if (err < 0)
···
 
 register_expr:
 	unregister_netdevice_notifier(&flow_offload_netdev_notifier);
+err:
 	return err;
 }