linux-kernel - Re: [PATCH v6 3/5] seccomp: add a way to get a listener fd from ptrace

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Message-ID: <CAMkWEXNN2_saQN-yQ7Pwgau1YTYQQuih+KLnKj5-cOYa6CyMPw@mail.gmail.com>
Date:   Wed, 17 Oct 2018 07:25:00 +0000
From:   Michael Tirado <mtirado418@...il.com>
To:     Andy Lutomirski <luto@...capital.net>,
        Tycho Andersen <tycho@...ho.ws>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v6 3/5] seccomp: add a way to get a listener fd from ptrace

On Thu, Sep 13, 2018 at 12:02 AM Andy Lutomirski <luto@...capital.net> wrote:
>
> Or we could have a
> seccomp() mode that adds a filter but only kicks in after execve().
>
> --Andy

Hey that's a pretty good idea, then we could block execve in a seccomp
launcher without post-exec cooperation, or that patch I wrote that used
an execve counter which probably should have been through prctl instead.

As for the rest of this long thread,
has anyone mentioned a specific use case that I missed? I didn't see code
patches sent to the linux-kernel mailing list, only this discussion thread
so I'm probably missing some important context.  Was it for loading modules
into kernel from a container?  Couldn't that be handled completely in user
space without using seccomp at all? Do we really want to turn seccomp into
a container IPC mechanism? It seems out of scope IMO, and especially
if it could be handled in user space already.

Why does it have to be a file descriptor, what would you be writing back to?
Could waitid be used somehow instead of ptrace to get notification
from a filter?
tldr, can someone kindly tell me how to find all the details surrounding these
patches so I can stop making really bad guesses?