[PATCH v1 net] rtnetlink: Use register_pernet_subsys() in rtnl_net_debug_init().

[PATCH v1 net] rtnetlink: Use register_pernet_subsys() in rtnl_net_debug_init().

[Kuniyuki Iwashima]

rtnl_net_debug_init() registers rtnl_net_debug_net_ops by
register_pernet_device() but calls unregister_pernet_subsys()
in case register_netdevice_notifier() fails.

It corrupts pernet_list because first_device is not updated
in unregister_pernet_device().

Let's fix it by calling register_pernet_subsys() instead.

The _subsys() one fits better for the use case because it keeps
the notifier alive until default_device_exit_net(), giving it
more chance to test NETDEV_UNREGISTER.

Fixes: 03fa53485659 ("rtnetlink: Add ASSERT_RTNL_NET() placeholder for netdev notifier.")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
---
 net/core/rtnl_net_debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/rtnl_net_debug.c b/net/core/rtnl_net_debug.c
index 7ecd28cc1c22..f3272b09c255 100644
--- a/net/core/rtnl_net_debug.c
+++ b/net/core/rtnl_net_debug.c
@@ -102,7 +102,7 @@ static int __init rtnl_net_debug_init(void)
 {
 	int ret;
 
-	ret = register_pernet_device(&rtnl_net_debug_net_ops);
+	ret = register_pernet_subsys(&rtnl_net_debug_net_ops);
 	if (ret)
 		return ret;
 
-- 
2.48.1

Re: [PATCH v1 net] rtnetlink: Use register_pernet_subsys() in rtnl_net_debug_init().

[Simon Horman]

On Fri, Mar 28, 2025 at 03:04:48PM -0700, Kuniyuki Iwashima wrote:
> rtnl_net_debug_init() registers rtnl_net_debug_net_ops by
> register_pernet_device() but calls unregister_pernet_subsys()
> in case register_netdevice_notifier() fails.
> 
> It corrupts pernet_list because first_device is not updated
> in unregister_pernet_device().

Hi Iwashima-san,

Maybe I am confused, but should the above line refer to
unregister_pernet_subsys()?

And perhaps it would be yet clearer to say something like:

It corrupts pernet_list because first_device is not updated
in register_pernet_device() but not unregister_pernet_subsys()?

> 
> Let's fix it by calling register_pernet_subsys() instead.
> 
> The _subsys() one fits better for the use case because it keeps
> the notifier alive until default_device_exit_net(), giving it
> more chance to test NETDEV_UNREGISTER.
> 
> Fixes: 03fa53485659 ("rtnetlink: Add ASSERT_RTNL_NET() placeholder for netdev notifier.")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>

...

Re: [PATCH v1 net] rtnetlink: Use register_pernet_subsys() in rtnl_net_debug_init().

[Kuniyuki Iwashima]

From: Simon Horman <horms@kernel.org>
Date: Mon, 31 Mar 2025 16:48:49 +0100
> On Fri, Mar 28, 2025 at 03:04:48PM -0700, Kuniyuki Iwashima wrote:
> > rtnl_net_debug_init() registers rtnl_net_debug_net_ops by
> > register_pernet_device() but calls unregister_pernet_subsys()
> > in case register_netdevice_notifier() fails.
> > 
> > It corrupts pernet_list because first_device is not updated
> > in unregister_pernet_device().
> 
> Hi Iwashima-san,
> 
> Maybe I am confused, but should the above line refer to
> unregister_pernet_subsys()?

Ah, exactly :)


> 
> And perhaps it would be yet clearer to say something like:
> 
> It corrupts pernet_list because first_device is not updated
> in register_pernet_device() but not unregister_pernet_subsys()?

Will rewrite in v2.

Thanks!