From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Mon, 6 Jan 2025 07:07:49 +0000 (+0900)
Subject: net: Hold __rtnl_net_lock() in (un)?register_netdevice_notifier().
X-Git-Tag: block-6.14-20240131~28^2~124^2~2
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=a239e0625097bccdd4065390952fe9e6d0fdf02b;p=linux-block.git

net: Hold __rtnl_net_lock() in (un)?register_netdevice_notifier().

(un)?register_netdevice_notifier() hold pernet_ops_rwsem and RTNL,
iterate all netns, and trigger the notifier for all netdev.

Let's hold __rtnl_net_lock() before triggering the notifier.

Note that we will need protection for netdev_chain when RTNL is
removed.  (e.g. blocking_notifier conversion [0] with a lockdep
annotation [1])

Link: https://lore.kernel.org/netdev/20250104063735.36945-2-kuniyu@amazon.com/ [0]
Link: https://lore.kernel.org/netdev/20250105075957.67334-1-kuniyu@amazon.com/ [1]
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250106070751.63146-2-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/net/core/dev.c b/net/core/dev.c
index 2179da3dfffc..34ded7974675 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1769,14 +1769,19 @@ int register_netdevice_notifier(struct notifier_block *nb)
 
 	/* Close race with setup_net() and cleanup_net() */
 	down_write(&pernet_ops_rwsem);
+
+	/* When RTNL is removed, we need protection for netdev_chain. */
 	rtnl_lock();
+
 	err = raw_notifier_chain_register(&netdev_chain, nb);
 	if (err)
 		goto unlock;
 	if (dev_boot_phase)
 		goto unlock;
 	for_each_net(net) {
+		__rtnl_net_lock(net);
 		err = call_netdevice_register_net_notifiers(nb, net);
+		__rtnl_net_unlock(net);
 		if (err)
 			goto rollback;
 	}
@@ -1787,8 +1792,11 @@ unlock:
 	return err;
 
 rollback:
-	for_each_net_continue_reverse(net)
+	for_each_net_continue_reverse(net) {
+		__rtnl_net_lock(net);
 		call_netdevice_unregister_net_notifiers(nb, net);
+		__rtnl_net_unlock(net);
+	}
 
 	raw_notifier_chain_unregister(&netdev_chain, nb);
 	goto unlock;
@@ -1821,8 +1829,11 @@ int unregister_netdevice_notifier(struct notifier_block *nb)
 	if (err)
 		goto unlock;
 
-	for_each_net(net)
+	for_each_net(net) {
+		__rtnl_net_lock(net);
 		call_netdevice_unregister_net_notifiers(nb, net);
+		__rtnl_net_unlock(net);
+	}
 
 unlock:
 	rtnl_unlock();