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, 5 deletions

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 999a982ad3fd..dc60bf585966 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3018,10 +3018,14 @@ int __init ip6_route_init(void)
         if (ret)
                 goto out_kmem_cache;
 
-        ret = register_pernet_subsys(&ip6_route_net_ops);
+        ret = fib6_init();
         if (ret)
                 goto out_dst_entries;
 
+        ret = register_pernet_subsys(&ip6_route_net_ops);
+        if (ret)
+                goto out_fib6_init;
+
         ip6_dst_blackhole_ops.kmem_cachep = ip6_dst_ops_template.kmem_cachep;
 
         /* Registering of the loopback is done before this portion of code,
@@ -3035,13 +3039,13 @@ int __init ip6_route_init(void)
         init_net.ipv6.ip6_blk_hole_entry->dst.dev = init_net.loopback_dev;
         init_net.ipv6.ip6_blk_hole_entry->rt6i_idev = in6_dev_get(init_net.loopback_dev);
   #endif
-        ret = fib6_init();
+        ret = fib6_init_late();
         if (ret)
                 goto out_register_subsys;
 
         ret = xfrm6_init();
         if (ret)
-                goto out_fib6_init;
+                goto out_fib6_init_late;
 
         ret = fib6_rules_init();
         if (ret)
@@ -3064,10 +3068,12 @@ fib6_rules_init:
         fib6_rules_cleanup();
 xfrm6_init:
         xfrm6_fini();
-out_fib6_init:
-        fib6_gc_cleanup();
+out_fib6_init_late:
+        fib6_cleanup_late();
 out_register_subsys:
         unregister_pernet_subsys(&ip6_route_net_ops);
+out_fib6_init:
+        fib6_gc_cleanup();
 out_dst_entries:
         dst_entries_destroy(&ip6_dst_blackhole_ops);
 out_kmem_cache: