netdev - Re: [PATCH v4] ipvs: Defer ip_vs_ftp unregister during netns cleanup

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Message-ID: <0effae4a-4b9d-552e-5de7-756af4627451@ssi.bg>
Date: Sat, 13 Sep 2025 20:23:04 +0300 (EEST)
From: Julian Anastasov <ja@....bg>
To: Slavin Liu <slavin452@...il.com>
cc: Simon Horman <horms@...ge.net.au>, Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, lvs-devel@...r.kernel.org,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] ipvs: Defer ip_vs_ftp unregister during netns
 cleanup


	Hello,

On Fri, 12 Sep 2025, Slavin Liu wrote:

> On the netns cleanup path, __ip_vs_ftp_exit() may unregister ip_vs_ftp
> before connections with valid cp->app pointers are flushed, leading to a
> use-after-free.
> 
> Fix this by introducing a global `exiting_module` flag, set to true in
> ip_vs_ftp_exit() before unregistering the pernet subsystem. In
> __ip_vs_ftp_exit(), skip ip_vs_ftp unregister if called during netns
> cleanup (when module_removing is false) and defer it to

	Pablo, can you change here module_removing to exiting_module 
before applying?

> __ip_vs_cleanup_batch(), which unregisters all apps after all connections
> are flushed. If called during module exit, unregister ip_vs_ftp
> immediately.
> 
> Fixes: 61b1ab4583e2 ("IPVS: netns, add basic init per netns.")
> Suggested-by: Julian Anastasov <ja@....bg>
> Signed-off-by: Slavin Liu <slavin452@...il.com>

	Looks good to me for the nf tree after above text is
changed, thanks!

Signed-off-by: Julian Anastasov <ja@....bg>

> ---
>  net/netfilter/ipvs/ip_vs_ftp.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/netfilter/ipvs/ip_vs_ftp.c b/net/netfilter/ipvs/ip_vs_ftp.c
> index d8a284999544..206c6700e200 100644
> --- a/net/netfilter/ipvs/ip_vs_ftp.c
> +++ b/net/netfilter/ipvs/ip_vs_ftp.c
> @@ -53,6 +53,7 @@ enum {
>  	IP_VS_FTP_EPSV,
>  };
>  
> +static bool exiting_module;
>  /*
>   * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
>   * First port is set to the default port.
> @@ -605,7 +606,7 @@ static void __ip_vs_ftp_exit(struct net *net)
>  {
>  	struct netns_ipvs *ipvs = net_ipvs(net);
>  
> -	if (!ipvs)
> +	if (!ipvs || !exiting_module)
>  		return;
>  
>  	unregister_ip_vs_app(ipvs, &ip_vs_ftp);
> @@ -627,6 +628,7 @@ static int __init ip_vs_ftp_init(void)
>   */
>  static void __exit ip_vs_ftp_exit(void)
>  {
> +	exiting_module = true;
>  	unregister_pernet_subsys(&ip_vs_ftp_ops);
>  	/* rcu_barrier() is called by netns */
>  }
> -- 
> 2.34.1

Regards

--
Julian Anastasov <ja@....bg>