ipv6: Prevent access to uninitialized fib_table_hash via /proc/net/ipv6_route

/proc/net/ipv6_route reflects the contents of fib_table_hash. The proc
handler is installed in ip6_route_net_init() whereas fib_table_hash is
allocated in fib6_net_init() _after_ the proc handler has been installed.

This opens up a short time frame to access fib_table_hash with its pants
down.

fib6_init() as a whole can't be moved to an earlier position as it also
registers the rtnetlink message handlers which should be registered at
the end. Therefore split it into fib6_init() which is run early and
fib6_init_late() to register the rtnetlink message handlers.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Reviewed-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 7 deletions

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 74c21b924a7..fbd4afff05f 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1692,21 +1692,25 @@ int __init fib6_init(void)
 	ret = register_pernet_subsys(&fib6_net_ops);
 	if (ret)
 		goto out_kmem_cache_create;
-
-	ret = __rtnl_register(PF_INET6, RTM_GETROUTE, NULL, inet6_dump_fib,
-			      NULL);
-	if (ret)
-		goto out_unregister_subsys;
 out:
 	return ret;
 
-out_unregister_subsys:
-	unregister_pernet_subsys(&fib6_net_ops);
 out_kmem_cache_create:
 	kmem_cache_destroy(fib6_node_kmem);
 	goto out;
 }
 
+int __init fib6_init_late(void)
+{
+	return __rtnl_register(PF_INET6, RTM_GETROUTE, NULL, inet6_dump_fib,
+			       NULL);
+}
+
+void fib6_cleanup_late(void)
+{
+	rtnl_unregister(PF_INET6, RTM_GETROUTE);
+}
+
 void fib6_gc_cleanup(void)
 {
 	unregister_pernet_subsys(&fib6_net_ops);