netfilter: Rework xt_TEE netdevice notifier

Register netdevice notifier for every iptable entry
is not good, since this breaks modularity, and
the hidden synchronization is based on rtnl_lock().

This patch reworks the synchronization via new lock,
while the rest of logic remains as it was before.
This is required for the next patch.

Tested via:

while :; do
	unshare -n iptables -t mangle -A OUTPUT -j TEE --gateway 1.1.1.2 --oif lo;
done

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/netfilter/xt_TEE.c b/net/netfilter/xt_TEE.c
index 86b0580..475957c 100644 (file)
--- a/net/netfilter/xt_TEE.c
+++ b/net/netfilter/xt_TEE.c
@@ -20,7 +20,7 @@
 #include <linux/netfilter/xt_TEE.h>
 
 struct xt_tee_priv {
-       struct notifier_block   notifier;
+       struct list_head        list;
        struct xt_tee_tginfo    *tginfo;
        int                     oif;
 };
@@ -51,29 +51,35 @@ 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 xt_tee_priv *priv;
 
-       priv = container_of(this, struct xt_tee_priv, notifier);
-       switch (event) {
-       case NETDEV_REGISTER:
-               if (!strcmp(dev->name, priv->tginfo->oif))
-                       priv->oif = dev->ifindex;
-               break;
-       case NETDEV_UNREGISTER:
-               if (dev->ifindex == priv->oif)
-                       priv->oif = -1;
-               break;
-       case NETDEV_CHANGENAME:
-               if (!strcmp(dev->name, priv->tginfo->oif))
-                       priv->oif = dev->ifindex;
-               else if (dev->ifindex == priv->oif)
-                       priv->oif = -1;
-               break;
+       mutex_lock(&priv_list_mutex);
+       list_for_each_entry(priv, &priv_list, list) {
+               switch (event) {
+               case NETDEV_REGISTER:
+                       if (!strcmp(dev->name, priv->tginfo->oif))
+                               priv->oif = dev->ifindex;
+                       break;
+               case NETDEV_UNREGISTER:
+                       if (dev->ifindex == priv->oif)
+                               priv->oif = -1;
+                       break;
+               case NETDEV_CHANGENAME:
+                       if (!strcmp(dev->name, priv->tginfo->oif))
+                               priv->oif = dev->ifindex;
+                       else if (dev->ifindex == priv->oif)
+                               priv->oif = -1;
+                       break;
+               }
        }
+       mutex_unlock(&priv_list_mutex);
 
        return NOTIFY_DONE;
 }
@@ -89,8 +95,6 @@ static int tee_tg_check(const struct xt_tgchk_param *par)
                return -EINVAL;
 
        if (info->oif[0]) {
-               int ret;
-
                if (info->oif[sizeof(info->oif)-1] != '\0')
                        return -EINVAL;
 
@@ -100,14 +104,11 @@ static int tee_tg_check(const struct xt_tgchk_param *par)
 
                priv->tginfo  = info;
                priv->oif     = -1;
-               priv->notifier.notifier_call = tee_netdev_event;
                info->priv    = priv;
 
-               ret = register_netdevice_notifier(&priv->notifier);
-               if (ret) {
-                       kfree(priv);
-                       return ret;
-               }
+               mutex_lock(&priv_list_mutex);
+               list_add(&priv->list, &priv_list);
+               mutex_unlock(&priv_list_mutex);
        } else
                info->priv = NULL;
 
@@ -120,7 +121,9 @@ static void tee_tg_destroy(const struct xt_tgdtor_param *par)
        struct xt_tee_tginfo *info = par->targinfo;
 
        if (info->priv) {
-               unregister_netdevice_notifier(&info->priv->notifier);
+               mutex_lock(&priv_list_mutex);
+               list_del(&info->priv->list);
+               mutex_unlock(&priv_list_mutex);
                kfree(info->priv);
        }
        static_key_slow_dec(&xt_tee_enabled);
@@ -153,13 +156,29 @@ static struct xt_target tee_tg_reg[] __read_mostly = {
 #endif
 };
 
+static struct notifier_block tee_netdev_notifier = {
+       .notifier_call = tee_netdev_event,
+};
+
 static int __init tee_tg_init(void)
 {
-       return xt_register_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
+       int ret;
+
+       ret = xt_register_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
+       if (ret)
+               return ret;
+       ret = register_netdevice_notifier(&tee_netdev_notifier);
+       if (ret) {
+               xt_unregister_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
+               return ret;
+       }
+
+       return 0;
 }
 
 static void __exit tee_tg_exit(void)
 {
+       unregister_netdevice_notifier(&tee_netdev_notifier);
        xt_unregister_targets(tee_tg_reg, ARRAY_SIZE(tee_tg_reg));
 }