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
__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@ssi.bg>
Signed-off-by: Slavin Liu <slavin452@gmail.com>
---
 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

	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@ssi.bg>
> Signed-off-by: Slavin Liu <slavin452@gmail.com>

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

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

Julian Anastasov <ja@ssi.bg> wrote:
> > Fixes: 61b1ab4583e2 ("IPVS: netns, add basic init per netns.")
> > Suggested-by: Julian Anastasov <ja@ssi.bg>
> > Signed-off-by: Slavin Liu <slavin452@gmail.com>
> 
> 	Looks good to me for the nf tree after above text is
> changed, thanks!

Thaks Julian for reviewing, i pushed it to nf:testing.