netns: fix addrconf_ifdown kernel panic

When a network namespace is destroyed the network interfaces are
all unregistered, making addrconf_ifdown called by the netdevice
notifier.
In the other hand, the addrconf exit method does a loop on the network
devices and does addrconf_ifdown on each of them. But the ordering of
the netns subsystem is not right because it uses the register_pernet_device
instead of register_pernet_subsys. If we handle the loopback as
any network device, we can safely use register_pernet_subsys.

But if we use register_pernet_subsys, the addrconf exit method will do
exactly what was already done with the unregistering of the network
devices. So in definitive, this code is pointless.

I removed the netns addrconf exit method and moved the code to the
addrconf cleanup function.

Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 40fabde..1220e2c 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2611,9 +2611,6 @@ static int addrconf_ifdown(struct net_device *dev, int how)
 
        ASSERT_RTNL();
 
-       if ((dev->flags & IFF_LOOPBACK) && how == 1)
-               how = 0;
-
        rt6_ifdown(net, dev);
        neigh_ifdown(&nd_tbl, dev);
 
@@ -4448,25 +4445,6 @@ int unregister_inet6addr_notifier(struct notifier_block *nb)
 
 EXPORT_SYMBOL(unregister_inet6addr_notifier);
 
-static void addrconf_net_exit(struct net *net)
-{
-       struct net_device *dev;
-
-       rtnl_lock();
-       /* clean dev list */
-       for_each_netdev(net, dev) {
-               if (__in6_dev_get(dev) == NULL)
-                       continue;
-               addrconf_ifdown(dev, 1);
-       }
-       addrconf_ifdown(net->loopback_dev, 2);
-       rtnl_unlock();
-}
-
-static struct pernet_operations addrconf_net_ops = {
-       .exit = addrconf_net_exit,
-};
-
 /*
  *     Init / cleanup code
  */
@@ -4508,10 +4486,6 @@ int __init addrconf_init(void)
        if (err)
                goto errlo;
 
-       err = register_pernet_device(&addrconf_net_ops);
-       if (err)
-               return err;
-
        register_netdevice_notifier(&ipv6_dev_notf);
 
        addrconf_verify(0);
@@ -4541,15 +4515,22 @@ errlo:
 void addrconf_cleanup(void)
 {
        struct inet6_ifaddr *ifa;
+       struct net_device *dev;
        int i;
 
        unregister_netdevice_notifier(&ipv6_dev_notf);
-       unregister_pernet_device(&addrconf_net_ops);
-
        unregister_pernet_subsys(&addrconf_ops);
 
        rtnl_lock();
 
+       /* clean dev list */
+       for_each_netdev(&init_net, dev) {
+               if (__in6_dev_get(dev) == NULL)
+                       continue;
+               addrconf_ifdown(dev, 1);
+       }
+       addrconf_ifdown(init_net.loopback_dev, 2);
+
        /*
         *      Check hash table.
         */
@@ -4570,6 +4551,4 @@ void addrconf_cleanup(void)
 
        del_timer(&addr_chk_timer);
        rtnl_unlock();
-
-       unregister_pernet_subsys(&addrconf_net_ops);
 }