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

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Message-ID: <20181021160045.GA25202@cisco>
Date:   Sun, 21 Oct 2018 17:00:45 +0100
From:   Tycho Andersen <tycho@...ho.ws>
To:     Michael Tirado <mtirado418@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH v6 3/5] seccomp: add a way to get a listener fd from
 ptrace

On Wed, Oct 17, 2018 at 06:15:47PM +0000, Michael Tirado wrote:
> Tycho, Sorry for the duplicate, I forgot to CC the list :(
> 
> On Wed, Oct 17, 2018 at 3:00 PM Tycho Andersen <tycho@...ho.ws> wrote:
> >
> >
> > That's one of the use cases, but there are a large number of others. I
> > discuss a few in patch 1:
> > https://www.spinics.net/lists/linux-containers/msg33956.html
> >
> 
> Thanks this is making more sense to me now.
> 
> I haven't been keeping up with the list and just did a bunch
> of reading. It seems that stackable LSM's are making some real
> progress now, and I wonder if those patches are merged would
> using a stacked security module approach be worth exploring if
> it provides the same or greater flexibility, and assuming all
> syscalls of interest can be hooked somehow?

Sorry, I somehow just noticed that this was a duplicate and the one I
replied to was the off-list one. Anyway, no, I don't think that'll
work. The LSM code right now can't do anything besides refuse an
access, and that's a very specific design constraint of it. In
particular, it can't mutate any task state or anything.

What we want in this series is basically the equivalent of
SECCOMP_RET_TRACE, without having to involve ptrace (for a variety of
reasons, mostly that applications want to use ptrace for their own
things). So seccomp seems like the most natural fit.

Tycho