ipv6: don't call fib6_run_gc() until routing is ready

When loading the ipv6 module, ndisc_init() is called before
ip6_route_init(). As the former registers a handler calling
fib6_run_gc(), this opens a window to run the garbage collector
before necessary data structures are initialized. If a network
device is initialized in this window, adding MAC address to it
triggers a NETDEV_CHANGEADDR event, leading to a crash in
fib6_clean_all().

Take the event handler registration out of ndisc_init() into a
separate function ndisc_late_init() and move it after
ip6_route_init().
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ndisc.h

@@ -190,7 +190,9 @@ static inline struct neighbour *__ipv6_neigh_lookup(struct net_device *dev, cons
 }
 
 extern int			ndisc_init(void);
+extern int			ndisc_late_init(void);
 
+extern void			ndisc_late_cleanup(void);
 extern void			ndisc_cleanup(void);
 
 extern int			ndisc_rcv(struct sk_buff *skb);

net/ipv6/af_inet6.c

@@ -915,6 +915,9 @@ static int __init inet6_init(void)
 	err = ip6_route_init();
 	if (err)
 		goto ip6_route_fail;
+	err = ndisc_late_init();
+	if (err)
+		goto ndisc_late_fail;
 	err = ip6_flowlabel_init();
 	if (err)
 		goto ip6_flowlabel_fail;
@@ -981,6 +984,8 @@ static int __init inet6_init(void)
 addrconf_fail:
 	ip6_flowlabel_cleanup();
 ip6_flowlabel_fail:
+	ndisc_late_cleanup();
+ndisc_late_fail:
 	ip6_route_cleanup();
 ip6_route_fail:
 #ifdef CONFIG_PROC_FS
@@ -1043,6 +1048,7 @@ static void __exit inet6_exit(void)
 	ipv6_exthdrs_exit();
 	addrconf_cleanup();
 	ip6_flowlabel_cleanup();
+	ndisc_late_cleanup();
 	ip6_route_cleanup();
 #ifdef CONFIG_PROC_FS
 

net/ipv6/ndisc.c

@@ -1727,24 +1727,28 @@ int __init ndisc_init(void)
 	if (err)
 		goto out_unregister_pernet;
 #endif
-	err = register_netdevice_notifier(&ndisc_netdev_notifier);
-	if (err)
-		goto out_unregister_sysctl;
 out:
 	return err;
 
-out_unregister_sysctl:
 #ifdef CONFIG_SYSCTL
-	neigh_sysctl_unregister(&nd_tbl.parms);
 out_unregister_pernet:
-#endif
 	unregister_pernet_subsys(&ndisc_net_ops);
 	goto out;
+#endif
 }
 
-void ndisc_cleanup(void)
+int __init ndisc_late_init(void)
+{
+	return register_netdevice_notifier(&ndisc_netdev_notifier);
+}
+
+void ndisc_late_cleanup(void)
 {
 	unregister_netdevice_notifier(&ndisc_netdev_notifier);
+}
+
+void ndisc_cleanup(void)
+{
 #ifdef CONFIG_SYSCTL
 	neigh_sysctl_unregister(&nd_tbl.parms);
 #endif