Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
In-Reply-To: <20180531144949.24995-1-tycho@tycho.ws>
References: <20180531144949.24995-1-tycho@tycho.ws>
From:   Kees Cook <keescook@chromium.org>
Date:   Fri, 8 Jun 2018 09:29:42 -0700
Message-ID: <CAGXu5jKsLDSBjB74SrvCvmGy_RTEjBsMtR5dk1CcRFrHEQfM_g@mail.gmail.com>
Subject: Re: [PATCH v3 0/4] seccomp trap to userspace
To:     Tycho Andersen <tycho@tycho.ws>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Linux Containers <containers@lists.linux-foundation.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Oleg Nesterov <oleg@redhat.com>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        "Serge E . Hallyn" <serge@hallyn.com>,
        Christian Brauner <christian.brauner@ubuntu.com>,
        Tyler Hicks <tyhicks@canonical.com>,
        Akihiro Suda <suda.akihiro@lab.ntt.co.jp>,
        "Tobin C . Harding" <me@tobin.cc>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, May 31, 2018 at 7:49 AM, Tycho Andersen <tycho@tycho.ws> wrote:
> Hi all,
>
> Here's a v3 of the seccomp trap to userspace, with all the nits from v2
> fixed. Open questions from v2 are still:
>
> 1. is it ok not to use netlink?

Yeah, I think there isn't a sensible way to reuse that API, which is
too bad. Let's just try to keep this interface future-proofed. :)

> 2. what should the fd passing API look like? (see patch notes on this
>    one for details of why the current one might (?) be a problem)

The only thing in my mind is avoiding the problems with other fd
passing API (e.g. when do rlimits get checked, etc).

> As an added bonus, I've also written some stress testing, with lots of
> tasks and listeners (1000 of each) sharing the same notification thread,
> and not found any issues so far. Code is here:
> https://github.com/tych0/kernel-utils/blob/master/seccomp/notify_stress.c
> although I haven't included it in the patchset.

That's excellent, thanks!

> v2: https://lkml.org/lkml/2018/5/17/627
>
> Tycho Andersen (4):
>   seccomp: add a return code to trap to userspace
>   seccomp: make get_nth_filter available outside of CHECKPOINT_RESTORE
>   seccomp: add a way to get a listener fd from ptrace
>   seccomp: add support for passing fds via USER_NOTIF

I'm under a time crunch with the merge window, but after -rc2 I should
have time to give this some close review. FWIW, I expect this to enter
-next this cycle and get it into the 4.19 merge window: we need the
feature and the alternatives have been well explored and don't look
workable.

Thanks for the series!

-Kees

-- 
Kees Cook
Pixel Security