net: reinstate rtnl in call_netdevice_notifiers()

Eric Biederman pointed out that not holding RTNL while calling
call_netdevice_notifiers() was racy.

This patch is a direct transcription his feedback
against commit 0115e8e30d6fc (net: remove delay at device dismantle)

Thanks Eric !

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Mahesh Bandewar <maheshb@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Gao feng <gaofeng@cn.fujitsu.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 5 deletions

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index fd7d9ae64f16..acdee325d972 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1050,9 +1050,6 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
                 return NOTIFY_DONE;
         }
 
-        if (event == NETDEV_UNREGISTER_FINAL)
-                return NOTIFY_DONE;
-
         in_dev = __in_dev_get_rtnl(dev);
 
         switch (event) {
@@ -1064,14 +1061,14 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
                 fib_sync_up(dev);
 #endif
                 atomic_inc(&net->ipv4.dev_addr_genid);
-                rt_cache_flush(dev_net(dev), -1);
+                rt_cache_flush(net, -1);
                 break;
         case NETDEV_DOWN:
                 fib_disable_ip(dev, 0, 0);
                 break;
         case NETDEV_CHANGEMTU:
         case NETDEV_CHANGE:
-                rt_cache_flush(dev_net(dev), 0);
+                rt_cache_flush(net, 0);
                 break;
         }
         return NOTIFY_DONE;