Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
MIME-Version: 1.0
References: <20220429043913.626647-1-davidgow@google.com> <YmuPFGrkzQYACgK0@kroah.com>
In-Reply-To: <YmuPFGrkzQYACgK0@kroah.com>
From:   David Gow <davidgow@google.com>
Date:   Sat, 30 Apr 2022 10:54:02 +0800
Message-ID: <CABVgOSmn3fTOr0LB3bUMJOzKTjNd6EMtSEKz5ZRfTfeF7DiE2w@mail.gmail.com>
Subject: Re: [PATCH] kunit: Taint kernel if any tests run
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Brendan Higgins <brendanhiggins@google.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kees Cook <keescook@chromium.org>,
        Shuah Khan <skhan@linuxfoundation.org>,
        "Guilherme G . Piccoli" <gpiccoli@igalia.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Sebastian Reichel <sre@kernel.org>,
        John Ogness <john.ogness@linutronix.de>,
        Joe Fradley <joefradley@google.com>,
        Daniel Latypov <dlatypov@google.com>,
        KUnit Development <kunit-dev@googlegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Apr 29, 2022 at 3:09 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Fri, Apr 29, 2022 at 12:39:14PM +0800, David Gow wrote:
> > KUnit tests are not supposed to run on production systems: they may do
> > deliberately illegal things to trigger errors, and have security
> > implications (assertions will often deliberately leak kernel addresses).
> >
> > Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been
> > run. This will be printed as 'N' (for kuNit, as K, U and T were already
> > taken).
> >
> > This should discourage people from running KUnit tests on production
> > systems, and to make it easier to tell if tests have been run
> > accidentally (by loading the wrong configuration, etc.)
> >
> > Signed-off-by: David Gow <davidgow@google.com>

< snip >

> > +     [ TAINT_KUNIT ]                 = { 'N', ' ', false },
>
> As kunit tests can be in modules, shouldn't this be "true" here?

Ah, good catch. While I tend to use either built-in tests (or modules
which are immediately unloaded), there are definitely some cases where
the tests are part of long-lasting modules.

I'll send out v2 with that changed.

> Overall, I like it, makes sense to me.  The "N" will take some getting
> used to, and I have no idea why "T" was for "struct randomization", that
> would have allowed you to use "T" instead.  Oh well.

Yeah, 'T' would've been nice, but I doubt it'd be worth trying to
change it now. At least we haven't had to resort to emoji...

Adding an actual name as Jani suggested would be a good idea, IMHO,
though obviously best done in a separate patch.


Cheers,
-- David