ipv6: add a missing unregister_pernet_subsys call

Clean up a missing exit path in the ipv6 module init routines. In
addrconf_init we call ipv6_addr_label_init which calls register_pernet_subsys
for the ipv6_addr_label_ops structure. But if module loading fails, or if the
ipv6 module is removed, there is no corresponding unregister_pernet_subsys call,
which leaves a now-bogus address on the pernet_list, leading to oopses in
subsequent registrations. This patch cleans up both the failed load path and
the unload path. Tested by myself with good results.

Signed-off-by: Neil Horman <[e-mail]>

include/net/addrconf.h | 1 +
net/ipv6/addrconf.c | 11 ++++++++---
net/ipv6/addrlabel.c | 5 +++++
3 files changed, 14 insertions(+), 3 deletions(-)
Signed-off-by: David S. Miller <[e-mail]>

include/net/addrconf.h

···
  *	IPv6 Address Label subsystem (addrlabel.c)
  */
 extern int			ipv6_addr_label_init(void);
+extern void			ipv6_addr_label_cleanup(void);
 extern void			ipv6_addr_label_rtnl_register(void);
 extern u32			ipv6_addr_label(struct net *net,
 						const struct in6_addr *addr,

net/ipv6/addrconf.c

···
 	if (err < 0) {
 		printk(KERN_CRIT "IPv6 Addrconf:"
 		       " cannot initialize default policy table: %d.\n", err);
-		return err;
+		goto out;
 	}
 
-	register_pernet_subsys(&addrconf_ops);
+	err = register_pernet_subsys(&addrconf_ops);
+	if (err < 0)
+		goto out_addrlabel;
 
 	/* The addrconf netdev notifier requires that loopback_dev
 	 * has it's ipv6 private information allocated and setup
···
 	unregister_netdevice_notifier(&ipv6_dev_notf);
 errlo:
 	unregister_pernet_subsys(&addrconf_ops);
-
+out_addrlabel:
+	ipv6_addr_label_cleanup();
+out:
 	return err;
 }
 
···
 
 	unregister_netdevice_notifier(&ipv6_dev_notf);
 	unregister_pernet_subsys(&addrconf_ops);
+	ipv6_addr_label_cleanup();
 
 	rtnl_lock();
 

net/ipv6/addrlabel.c

···
 	return register_pernet_subsys(&ipv6_addr_label_ops);
 }
 
+void ipv6_addr_label_cleanup(void)
+{
+	unregister_pernet_subsys(&ipv6_addr_label_ops);
+}
+
 static const struct nla_policy ifal_policy[IFAL_MAX+1] = {
 	[IFAL_ADDRESS]		= { .len = sizeof(struct in6_addr), },
 	[IFAL_LABEL]		= { .len = sizeof(u32), },