linux-kernel - Re: [PATCH v4 4/4] selftest: Taint kernel when test module loaded

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Message-ID: <CABVgOSnZwnQZAo5LH1KEbpVYvCtvTVCG4kZR=aV_gxFuU_D12g@mail.gmail.com>
Date:   Sat, 2 Jul 2022 12:06:12 +0800
From:   David Gow <davidgow@...gle.com>
To:     Luis Chamberlain <mcgrof@...nel.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>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Masahiro Yamada <masahiroy@...nel.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 Development <kunit-dev@...glegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Lucas De Marchi <lucas.demarchi@...el.com>,
        Aaron Tomlin <atomlin@...hat.com>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        Michal Marek <michal.lkml@...kovi.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH v4 4/4] selftest: Taint kernel when test module loaded

On Sat, Jul 2, 2022 at 6:33 AM Luis Chamberlain <mcgrof@...nel.org> wrote:
>
> On Fri, Jul 01, 2022 at 04:47:44PM +0800, David Gow wrote:
> > Make any kselftest test module (using the kselftest_module framework)
> > taint the kernel with TAINT_TEST on module load.
> >
> > Note that several selftests use kernel modules which are not based on
> > the kselftest_module framework, and so will not automatically taint the
> > kernel.
> >
> > This can be done in two ways:
> > - Moving the module to the tools/testing directory. All modules under
> >   this directory will taint the kernel.
> > - Adding the 'test' module property with:
> >   MODULE_INFO(test, "Y")
>
> This just needs to be documented somewhere other than a commit log.
> Otherwise I am not sure how we can be sure it will catch on.

I've updated the kselftest documentation for v5.

> > Similarly, selftests which do not load modules into the kernel generally
> > should not taint the kernel (or possibly should only do so on failure),
> > as it's assumed that testing from user-space should be safe. Regardless,
> > they can write to /proc/sys/kernel/tainted if required.
> >
> > Signed-off-by: David Gow <davidgow@...gle.com>
>
> Looks good otherwise!
>
> Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
>
> Do we want this to go through selftest / kunit / modules tree?
> Happy for it to through any. I can't predict a conflict.

I don't mind which tree it goes through either -- I'm not aware of
anything which would depend on it. I do have it on the list of things
pending for the KUnit tree, but it's much less KUnit-specific now
compared to v1. Regardless, I'll leave in the KUnit to-do list, and
we'll pick it up if no-one else particularly wants to.

Cheers,
-- David