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, 2 insertions, 0 deletions

diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 0ae759a6c76e..209af13b0336 100644
--- 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);