linux-kernel - Re: [PATCH v1 0/6] seccomp: Implement constant action bitmaps

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Date:   Thu, 24 Sep 2020 13:00:34 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrea Arcangeli <aarcange@...hat.com>
Cc:     YiFei Zhu <yifeifz2@...inois.edu>, Jann Horn <jannh@...gle.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Tycho Andersen <tycho@...ho.pizza>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        Giuseppe Scrivano <gscrivan@...hat.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Dimitrios Skarlatos <dskarlat@...cmu.edu>,
        Valentin Rothberg <vrothber@...hat.com>,
        Hubertus Franke <frankeh@...ibm.com>,
        Jack Chen <jianyan2@...inois.edu>,
        Josep Torrellas <torrella@...inois.edu>,
        Tianyin Xu <tyxu@...inois.edu>, bpf@...r.kernel.org,
        containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/6] seccomp: Implement constant action bitmaps

On Thu, Sep 24, 2020 at 02:57:02PM -0400, Andrea Arcangeli wrote:
> Hello,
> 
> I'm posting this only for the record, feel free to ignore.
> 
> On Wed, Sep 23, 2020 at 04:29:17PM -0700, Kees Cook wrote:
> > rfc: https://lore.kernel.org/lkml/20200616074934.1600036-1-keescook@chromium.org/
> > alternative: https://lore.kernel.org/containers/cover.1600661418.git.yifeifz2@illinois.edu/
> > v1:
> > - rebase to for-next/seccomp
> > - finish X86_X32 support for both pinning and bitmaps
> 
> It's pretty clear the O(1) seccomp filter bitmap was first was
> proposed by your RFC in June (albeit it was located in the wrong place
> and is still in the wrong place in v1).
> 
> > - replace TLB magic with Jann's emulator
>     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>     
> That's a pretty fundamental change in v1 compared to your the
> non-competing TLB magic technique you used in the RFC last June.
> 
> The bitmap isn't the clever part of the patch, the bitmap can be
> reviewed in seconds, the difficult part to implement and to review is
> how you fill the bitmap and in that respect there's absolutely nothing
> in common in between the "rfc:" and the "alternative" link.
> 
> In June your bitmap-filling engine was this:
> 
> https://lore.kernel.org/lkml/20200616074934.1600036-5-keescook@chromium.org/
> 
> Then on Sep 21 YiFei Zhu posted his new innovative BPF emulation
> innovation that obsoleted your TLB magic of June:
> 
> https://lists.linuxfoundation.org/pipermail/containers/2020-September/042153.html
> 
> And on Sep 23 instead of collaborating and helping YiFei Zhu to
> improve his BPF emulator, you posted the same technique that looks
> remarkably similar without giving YiFei Zhu any attribution and you
> instead attribute the whole idea to Jann Horn:
> 
> https://lkml.kernel.org/r/20200923232923.3142503-5-keescook@chromium.org

?? Because it IS literally Jann's code:
https://lore.kernel.org/lkml/CAG48ez1p=dR_2ikKq=xVxkoGg0fYpTBpkhJSv1w-6BG=76PAvw@mail.gmail.com/
As the first reply to 20200616074934.1600036-5-keescook@...omium.org. In
June. Which I agreed was the way to go. In June.

And When YiFei Zhu sent their series, I saw they were headed in
a direction that looked functionally similar, but significantly
over-engineered, and done without building on the June RFC and its
discussion. So I raised the priority of putting Jann's code in to the
RFC, so I could send out an update demonstrating both how small I would
like the emulator to be, and how to handle things like x32.

How, exactly, am I not collaborating? I was literally trying to
thread-merge and avoid (more) extra work on YiFei Zhu's end.

-- 
Kees Cook