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

[Julian Anastasov <ja@xxxxxx>]

        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@xxxxxx>
> Signed-off-by: Slavin Liu <slavin452@xxxxxxxxx>

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

Signed-off-by: Julian Anastasov <ja@xxxxxx>

> ---
>  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@xxxxxx>