Re: [PATCH net v3] gtp: Require 'CAP_NET_ADMIN' when joining the gtp multicast group

[Simon Horman <horms@kernel.org>]

On Thu, Oct 29, 2026 at 09:49:35AM +0530, Anil Kaushik wrote:
> On Thu, Oct 29, 2026 at 9:38 AM <netdev-bot+sashiko@kernel.org> wrote:
> >
> > Thank you for your contribution! Sashiko AI review found 1 potential
> > issue(s) to consider.
> >
> > Critical: 0 · High: 1 · Medium: 0 · Low: 0
> >
> > If you believe none of the issues are legitimate, please reply to each
> > issue of Medium severity or higher and explain why the AI is wrong.
> > If any of them are legitimate and you plan to respin, please let patchwork
> > know by including "pw-bot: cr" as a separate line at the end of your reply
> > (one such reply per series is enough).
> >
> > - [High] An unprivileged local user can still receive gtp multicast
> >   notifications (PDP add/delete and echo responses) by joining the…
> >
> > --
> >
> > gtp: Require 'CAP_NET_ADMIN' when joining the gtp multicast group
> >
> > This patch marks the gtp generic netlink multicast group with
> > GENL_MCAST_CAP_NET_ADMIN in drivers/net/gtp.c and with uns-admin-perm in
> > the gtp netlink spec. The goal is to stop unprivileged users from
> > receiving the PDP context add/delete and echo response notifications,
> > which carry the same data as a GETPDP reply.
> >
> 
> Yes, this works, but the gap is in the genetlink core, not in gtp.
> genl_unregister_mc_groups() clears the members of the IDs it frees, but
> nothing clears them when free IDs are given to a new family. So it hits
> every modular group with a GENL_MCAST_CAP_* flag, psample and
> drop_monitor too.
> 
> This patch is still needed, and it does not change. I will send a
> separate fix to net that clears the members of the new IDs in
> genl_validate_assign_mc_groups(), like the unregister path does.

Thanks Anil,

One step at a time seems like a good approach to me.

Reviewed-by: Simon Horman <horms@kernel.org>