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, 1 insertions, 5 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index e581009cb09e..6bc85f7c31e3 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2566,14 +2566,10 @@ static int addrconf_notify(struct notifier_block *this, unsigned long event,
                            void *data)
 {
         struct net_device *dev = (struct net_device *) data;
-        struct inet6_dev *idev;
+        struct inet6_dev *idev = __in6_dev_get(dev);
         int run_pending = 0;
         int err;
 
-        if (event == NETDEV_UNREGISTER_FINAL)
-                return NOTIFY_DONE;
-
-        idev = __in6_dev_get(dev);
         switch (event) {
         case NETDEV_REGISTER:
                 if (!idev && dev->mtu >= IPV6_MIN_MTU) {