netfilter: xt_TEE: fix wrong interface selection

TEE netdevice notifier handler checks only interface name. however
each netns can have same interface name. hence other netns's interface
could be selected.

test commands:
   %ip netns add vm1
   %iptables -I INPUT -p icmp -j TEE --gateway 192.168.1.1 --oif enp2s0
   %ip link set enp2s0 netns vm1

Above rule is in the root netns. but that rule could get enp2s0
ifindex of vm1 by notifier handler.

After this patch, TEE rule is added to the per-netns list.

Fixes: 9e2f6c5d78 ("netfilter: Rework xt_TEE netdevice notifier")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/xt_TEE.c

@@ -14,6 +14,8 @@
 #include <linux/skbuff.h>
 #include <linux/route.h>
 #include <linux/netfilter/x_tables.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
 #include <net/route.h>
 #include <net/netfilter/ipv4/nf_dup_ipv4.h>
 #include <net/netfilter/ipv6/nf_dup_ipv6.h>
@@ -25,8 +27,15 @@ struct xt_tee_priv {
 	int			oif;
 };
 
+static unsigned int tee_net_id __read_mostly;
 static const union nf_inet_addr tee_zero_address;
 
+struct tee_net {
+	struct list_head priv_list;
+	/* lock protects the priv_list */
+	struct mutex lock;
+};
+
 static unsigned int
 tee_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 {
@@ -51,17 +60,16 @@ tee_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 }
 #endif
 
-static DEFINE_MUTEX(priv_list_mutex);
-static LIST_HEAD(priv_list);
-
 static int tee_netdev_event(struct notifier_block *this, unsigned long event,
 			    void *ptr)
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct net *net = dev_net(dev);
+	struct tee_net *tn = net_generic(net, tee_net_id);
 	struct xt_tee_priv *priv;
 
-	mutex_lock(&priv_list_mutex);
-	list_for_each_entry(priv, &priv_list, list) {
+	mutex_lock(&tn->lock);
+	list_for_each_entry(priv, &tn->priv_list, list) {
 		switch (event) {
 		case NETDEV_REGISTER:
 			if (!strcmp(dev->name, priv->tginfo->oif))
@@ -79,13 +87,14 @@ static int tee_netdev_event(struct notifier_block *this, unsigned long event,
 			break;
 		}
 	}
-	mutex_unlock(&priv_list_mutex);
+	mutex_unlock(&tn->lock);
 
 	return NOTIFY_DONE;
 }
 
 static int tee_tg_check(const struct xt_tgchk_param *par)
 {
+	struct tee_net *tn = net_generic(par->net, tee_net_id);
 	struct xt_tee_tginfo *info = par->targinfo;
 	struct xt_tee_priv *priv;
 
@@ -106,9 +115,9 @@ static int tee_tg_check(const struct xt_tgchk_param *par)
 		priv->oif     = -1;
 		info->priv    = priv;
 
-		mutex_lock(&priv_list_mutex);
-		list_add(&priv->list, &priv_list);
-		mutex_unlock(&priv_list_mutex);
+		mutex_lock(&tn->lock);
+		list_add(&priv->list, &tn->priv_list);
+		mutex_unlock(&tn->lock);
 	} else
 		info->priv = NULL;
 
@@ -118,12 +127,13 @@ static int tee_tg_check(const struct xt_tgchk_param *par)
 
 static void tee_tg_destroy(const struct xt_tgdtor_param *par)
 {
+	struct tee_net *tn = net_generic(par->net, tee_net_id);
 	struct xt_tee_tginfo *info = par->targinfo;
 
 	if (info->priv) {
-		mutex_lock(&priv_list_mutex);
+		mutex_lock(&tn->lock);
 		list_del(&info->priv->list);
-		mutex_unlock(&priv_list_mutex);
+		mutex_unlock(&tn->lock);
 		kfree(info->priv);
 	}
 	static_key_slow_dec(&xt_tee_enabled);
@@ -156,6 +166,21 @@ static struct xt_target tee_tg_reg[] __read_mostly = {
 #endif
 };
 
+static int __net_init tee_net_init(struct net *net)
+{
+	struct tee_net *tn = net_generic(net, tee_net_id);
+
+	INIT_LIST_HEAD(&tn->priv_list);
+	mutex_init(&tn->lock);
+	return 0;
+}
+
+static struct pernet_operations tee_net_ops = {
+	.init = tee_net_init,
+	.id   = &tee_net_id,
+	.size = sizeof(struct tee_net),
+};
+
 static struct notifier_block tee_netdev_notifier = {
 	.notifier_call = tee_netdev_event,
 };
@@ -164,22 +189,32 @@ static int __init tee_tg_init(void)
 {
 	int ret;
 
+	ret = register_pernet_subsys(&tee_net_ops);
+	if (ret < 0)
+		return ret;
+
 	ret = xt_register_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
-	if (ret)
-		return ret;
+	if (ret < 0)
+		goto cleanup_subsys;
+
 	ret = register_netdevice_notifier(&tee_netdev_notifier);
-	if (ret) {
-		xt_unregister_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
-		return ret;
-	}
+	if (ret < 0)
+		goto unregister_targets;
 
 	return 0;
+
+unregister_targets:
+	xt_unregister_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
+cleanup_subsys:
+	unregister_pernet_subsys(&tee_net_ops);
+	return ret;
 }
 
 static void __exit tee_tg_exit(void)
 {
 	unregister_netdevice_notifier(&tee_netdev_notifier);
 	xt_unregister_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
+	unregister_pernet_subsys(&tee_net_ops);
 }
 
 module_init(tee_tg_init);