linux-kernel - Re: [PATCH] [RFC] signal: Add KUnit tests

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Message-ID: <202308170956.B7CA2B8BDB@keescook>
Date:   Thu, 17 Aug 2023 09:57:12 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Brendan Higgins <brendan.higgins@...ux.dev>,
        David Gow <davidgow@...gle.com>,
        Petr Skocik <pskocik@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jens Axboe <axboe@...nel.dk>, linux-kselftest@...r.kernel.org,
        kunit-dev@...glegroups.com,
        Frederic Weisbecker <frederic@...nel.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Mike Christie <michael.christie@...cle.com>,
        Marco Elver <elver@...gle.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        "haifeng.xu" <haifeng.xu@...pee.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] [RFC] signal: Add KUnit tests

On Wed, Aug 16, 2023 at 11:08:21PM -0500, Eric W. Biederman wrote:
> Kees Cook <keescook@...omium.org> writes:
> 
> > This is a continuation of the proposal[1] for mocking init_task for
> > KUnit testing. Changing the behavior of kill_something_info() is moving
> > forward[2] and I'd _really_ like to have some unit tests in place to
> > actually test the behavioral changes.
> >
> > I tried to incorporate feedback from Daniel and David, and I think the
> > result is fairly workable -- the only tricky part is building valid
> > task_struct instances. :)
> >
> > Notably, I haven't actually gotten as far as testing the actual proposed
> > behavioral change since I wanted to make sure this approach wasn't going
> > to totally crash and burn.
> >
> > Thoughts?
> 
> Overall this looks like a nice start.  More comments below.
> 
> I do wonder though.  Would it perhaps be easier to create a pid
> namespace with just the processes you want in it?

Do you have a short example of how I could do this correctly? It's not
obvious to me how to actually set all that up (and tear it down).

> I am wondering because you failed to mock find_vpid and so you
> are actually testing sending signals to kernel threads.

Hah. Eek.

-- 
Kees Cook