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>

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 0ae759a..209af13 100644 (file)
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -271,6 +271,8 @@ extern void                 fib6_run_gc(unsigned long expires,
 extern void                    fib6_gc_cleanup(void);
 
 extern int                     fib6_init(void);
+extern int                     fib6_init_late(void);
+extern void                    fib6_cleanup_late(void);
 
 #ifdef CONFIG_IPV6_MULTIPLE_TABLES
 extern int                     fib6_rules_init(void);

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 74c21b9..fbd4aff 100644 (file)
--- 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);

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 999a982..dc60bf5 100644 (file)
--- 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: