Re: [PATCH net] ipv4: nexthop: handle errors in nexthop_init()

[Ido Schimmel]

On Tue, Jul 28, 2026 at 11:10:55AM +0800, Minhong He wrote:
> nexthop_init() ignores errors from register_pernet_subsys(),
> register_netdevice_notifier() and rtnl_register_many(), so a partial
> initialization can appear successful.
> 
> Check each step and unwind the registrations that already succeeded.
> 
> Signed-off-by: Minhong He <heminhong@xxxxxxxxxx>
> ---
>  net/ipv4/nexthop.c | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
> index 6205bd57aa85..0ad40d93e3b5 100644
> --- a/net/ipv4/nexthop.c
> +++ b/net/ipv4/nexthop.c
> @@ -4192,12 +4192,26 @@ static const struct rtnl_msg_handler nexthop_rtnl_msg_handlers[] __initconst = {
>  
>  static int __init nexthop_init(void)
>  {
> -	register_pernet_subsys(&nexthop_net_ops);
> +	int err;
> +
> +	err = register_pernet_subsys(&nexthop_net_ops);
> +	if (err)
> +		return err;

This can only fail if the allocation of devhash didn't succeed, which
seems unlikely (boot + GFP_KERNEL), but OK.

>  
> -	register_netdevice_notifier(&nh_netdev_notifier);
> +	err = register_netdevice_notifier(&nh_netdev_notifier);
> +	if (err)
> +		goto err_unregister_pernet;

Can only fail if the notifier is already registered (not possible) or if
the NETDEV_{REGISTER,UP} replay fails which is also not possible given
that nh_netdev_event() always returns NOTIFY_DONE, but let's assume that
it's fragile and we can't rely on that.

>  
> -	rtnl_register_many(nexthop_rtnl_msg_handlers);
> +	err = rtnl_register_many(nexthop_rtnl_msg_handlers);
> +	if (err)
> +		goto err_unregister_notifier;

Panics upon failure.

So, I think you should drop the error handling from rtnl_register_many()
(explain why it can't fail in the commit message) and target net-next
given the lack of fixes tag and that the issue is theoretical.

>  
>  	return 0;
> +
> +err_unregister_notifier:
> +	unregister_netdevice_notifier(&nh_netdev_notifier);
> +err_unregister_pernet:
> +	unregister_pernet_subsys(&nexthop_net_ops);
> +	return err;
>  }
>  subsys_initcall(nexthop_init);
> -- 
> 2.25.1
>