Hello,
On Thu, 17 Sep 2026, Zihan Xi wrote:
> ip_vs_ftp_out() creates a wildcard data connection from the
> server-advertised passive port. If that port is one of the configured FTP
> control ports, ip_vs_conn_new() binds the FTP helper to the new connection
> again. A subsequent wildcard lookup can then extend a controlled-connection
> chain.
>
> Reject zero and configured control ports before creating passive
> connections. For active mode, reject a zero client port and a data port
> derived from a configured control port.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: [email protected]
> Reported-by: Vega <[email protected]>
> Assisted-by: LLM
> Co-developed-by: Luxing Yin <[email protected]>
> Signed-off-by: Luxing Yin <[email protected]>
> Signed-off-by: Zihan Xi <[email protected]>
Patch looks good to me for the nf tree, thanks!
Signed-off-by: Julian Anastasov <[email protected]>
> ---
> changes in v2:
> - Reject the data port derived from a configured control port in
> ip_vs_ftp_in() to cover the active-mode bypass.
> - v1 Link:
> https://lore.kernel.org/all/[email protected]/
>
> net/netfilter/ipvs/ip_vs_ftp.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/net/netfilter/ipvs/ip_vs_ftp.c b/net/netfilter/ipvs/ip_vs_ftp.c
> index 9e3e005a82635..4822a1a75212d 100644
> --- a/net/netfilter/ipvs/ip_vs_ftp.c
> +++ b/net/netfilter/ipvs/ip_vs_ftp.c
> @@ -62,6 +62,17 @@ static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
> module_param_array(ports, ushort, &ports_count, 0444);
> MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
>
> +static bool is_control_port(u16 port)
> +{
> + unsigned int i;
> +
> + for (i = 0; i < ports_count; i++) {
> + if (ports[i] == port)
> + return true;
> + }
> + return false;
> +}
> +
>
> static char *ip_vs_ftp_data_ptr(struct sk_buff *skb, struct ip_vs_iphdr
> *ipvsh)
> {
> @@ -319,6 +330,10 @@ static int ip_vs_ftp_out(struct ip_vs_app *app, struct
> ip_vs_conn *cp,
> return 1;
> }
>
> + /* Do not redirect data to control ports */
> + if (!port || is_control_port(ntohs(port)))
> + return 0;
> +
> /* Now update or create a connection entry for it */
> {
> struct ip_vs_conn_param p;
> @@ -529,6 +544,9 @@ static int ip_vs_ftp_in(struct ip_vs_app *app, struct
> ip_vs_conn *cp,
> return 1;
> }
>
> + if (!port || is_control_port(ntohs(cp->vport) - 1))
> + return 0;
> +
> /* Passive mode off */
> cp->app_data = (void *) IP_VS_FTP_ACTIVE;
>
> --
> 2.43.0
Regards
--
Julian Anastasov <[email protected]>
