Re: [PATCH net-next v6 1/3] scm: add SO_PASSPIDFD and SCM_PIDFD

From: Aleksandr Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
To: Jakub Kicinski <kuba@kernel.org>
Cc: Luca Boccassi <bluca@debian.org>,
	Christian Brauner <brauner@kernel.org>,
	davem@davemloft.net, linux-kernel@vger.kernel.org,
	netdev@vger.kernel.org, Eric Dumazet <edumazet@google.com>,
	Paolo Abeni <pabeni@redhat.com>,
	Leon Romanovsky <leon@kernel.org>,
	David Ahern <dsahern@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Kees Cook <keescook@chromium.org>,
	Kuniyuki Iwashima <kuniyu@amazon.com>,
	Lennart Poettering <mzxreary@0pointer.de>,
	linux-arch@vger.kernel.org
Subject: Re: [PATCH net-next v6 1/3] scm: add SO_PASSPIDFD and SCM_PIDFD
Date: Wed, 24 May 2023 12:43:36 +0200	[thread overview]
Message-ID: <CAEivzxeS2J5i0RJDvFHq-U_RAU5bbKVF5ZbphYDGoPcMZTsE3Q@mail.gmail.com> (raw)
In-Reply-To: <20230523140844.5895d645@kernel.org>

On Tue, May 23, 2023 at 11:08 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Tue, 23 May 2023 11:44:01 +0100 Luca Boccassi wrote:
> > > I really would like to avoid that because it will just mean that someone
> > > else will abuse that function and then make an argument why we should
> > > export the other function.
> > >
> > > I think it would be ok if we required that unix support is built in
> > > because it's not unprecedented either and we're not breaking anything.
> > > Bpf has the same requirement:
> > >
> > >   #if IS_BUILTIN(CONFIG_UNIX) && defined(CONFIG_BPF_SYSCALL)
> > >   struct bpf_unix_iter_state {
> > >           struct seq_net_private p;
> > >           unsigned int cur_sk;
> > >           unsigned int end_sk;
> > >           unsigned int max_sk;
> > >           struct sock **batch;
> > >           bool st_bucket_done;
> > >   };
> > >
> > > and
> > >
> > >   #if IS_BUILTIN(CONFIG_UNIX) && defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS)
> > >   DEFINE_BPF_ITER_FUNC(unix, struct bpf_iter_meta *meta,
> > >                        struct unix_sock *unix_sk, uid_t uid)
>
> Don't think we should bring BPF into arguments about uAPI consistency :S
>
> > Some data points: Debian, Ubuntu, Fedora, RHEL, CentOS, Archlinux all
> > ship with CONFIG_UNIX=y, so a missing SCM_PIDFD in unlikely to have a
> > widespread impact, and if it does, it might encourage someone to
> > review their kconfig.
>
> IDK how you can argue that everyone sets UNIX to =y so hiding SCM_PIDFD
> is fine and at the same time not be okay with making UNIX a bool :S
>
> > As mentioned on the v5 thread, we are waiting for this API to get the
> > userspace side sorted (systemd/dbus/dbus-broker/polkit), so I'd be
> > really grateful if we could start with the simplest and most
> > conservative approach (which seems to be the current one in v6 to me),
> > and then eventually later decide whether to export more functions, or
> > to deprecate CONFIG_UNIX=m, or something else entirely, as that
> > doesn't really affect the shape of the UAPI, just the details of its
> > availability. Thank you.
>
> Just throw in a patch to make UNIX a bool and stop arguing then.

Dear Jakub,

Thanks for your attention to these patch series!

I'm ready to prepare/send a patch to make CONFIG_UNIX bool.

I will send SO_PEERPIDFD as an independent patch too, because it
doesn't require this change with CONFIG_UNIX
and we can avoid waiting until CONFIG_UNIX change will be merged.
I've a feeling that the discussion around making CONFIG_UNIX  to be a
boolean won't be easy and fast ;-)

Kind regards,
Alex