[PATCH v4 net 3/3] dev: Use rtnl_net_dev_lock() in unregister_netdev().

[Kuniyuki Iwashima <kuniyu@amazon.com>]

The following sequence is basically illegal when dev was fetched
without lookup because dev_net(dev) might be different after holding
rtnl_net_lock():

  net = dev_net(dev);
  rtnl_net_lock(net);

Let's use rtnl_net_dev_lock() in unregister_netdev().

Note that there is no real bug in unregister_netdev() for now
because RTNL protects the scope even if dev_net(dev) is changed
before/after RTNL.

Fixes: 00fb9823939e ("dev: Hold per-netns RTNL in (un)?register_netdev().")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/core/dev.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 6a39fb5baa92..b6b1f597935f 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11934,11 +11934,9 @@ EXPORT_SYMBOL(unregister_netdevice_many);
  */
 void unregister_netdev(struct net_device *dev)
 {
-	struct net *net = dev_net(dev);
-
-	rtnl_net_lock(net);
+	rtnl_net_dev_lock(dev);
 	unregister_netdevice(dev);
-	rtnl_net_unlock(net);
+	rtnl_net_dev_unlock(dev);
 }
 EXPORT_SYMBOL(unregister_netdev);
 
-- 
2.39.5 (Apple Git-154)