netdev - [PATCH v2 net-next 1/3] net: Hold __rtnl_net_lock() in (un)?register_netdevice

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Message-ID: <20250106070751.63146-2-kuniyu@amazon.com>
Date: Mon, 6 Jan 2025 16:07:49 +0900
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, Simon Horman <horms@...nel.org>
CC: Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima
	<kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v2 net-next 1/3] 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@...zon.com>
---
 net/core/dev.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index e7223972b9aa..0096a81b474f 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 @@ int register_netdevice_notifier(struct notifier_block *nb)
 	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();
-- 
2.39.5 (Apple Git-154)