linux-kernel - Re: [PATCH v2] kunit: Taint kernel if any tests run

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Date:   Sun, 1 May 2022 11:24:28 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     David Gow <davidgow@...gle.com>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Lucas De Marchi <lucas.demarchi@...el.com>,
        Aaron Tomlin <atomlin@...hat.com>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org
Cc:     Brendan Higgins <brendanhiggins@...gle.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        "Guilherme G . Piccoli" <gpiccoli@...lia.com>,
        Sebastian Reichel <sre@...nel.org>,
        John Ogness <john.ogness@...utronix.de>,
        Joe Fradley <joefradley@...gle.com>,
        Daniel Latypov <dlatypov@...gle.com>,
        kunit-dev@...glegroups.com, linux-kselftest@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jani Nikula <jani.nikula@...ux.intel.com>
Subject: Re: [PATCH v2] kunit: Taint kernel if any tests run

On Sun, May 01, 2022 at 11:22:38AM -0700, Luis Chamberlain wrote:
> On Sat, Apr 30, 2022 at 11:00:19AM +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@...gle.com>
> 
> There is no reason to distinguish kunit from selftests if the result is
> the same: really make the kernel try really insane stupid things which
> may crash it or put it into a bad state.
> 
> So no, this should be renamed to "TEST_BREAK" as I think outside of
> selftest and kunit we may grow the kernel to do stupid things outside
> of that domain and this gives us the flexilibilty to use that in other
> places as well.
> 
> It begs the question if we *should* allow userspace to volunterally say
> "hey, we are doing really insane things, brace yourself." Why ? Well
> because selftest has tons of modules. We either then define a macro
> that adds the taint for them and wrap the module declaration for it,
> or we expose a syctl to let userspace volunteer to opt-in to seggest
> we are about to try something stupid with the kernel including loading
> some dangeerous modules which may not have macros which taint the kernel.
> That would let selftest taint on *any* selftest. Because we can run all
> selftests or run one selftest.
> 
> Then, if such sysctl is exposed, maybe we should then also use this for
> example for blktests, fstests, fio tests, etc.

For got to expand to fsdevel and linux-block.

  Luis