linux-kernel - Re: [PATCH v5 4/4] selftest: Taint kernel when test module loaded

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Message-ID: <CABVgOSmUrUuZm0eYkPF66mKEsj+CR4JFb9Km_e-0TbJYcK0fjQ@mail.gmail.com>
Date:   Sat, 2 Jul 2022 12:45:19 +0800
From:   David Gow <davidgow@...gle.com>
To:     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>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>
Cc:     "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 v5 4/4] selftest: Taint kernel when test module loaded

On Sat, Jul 2, 2022 at 12:10 PM David Gow <davidgow@...gle.com> wrote:
>
> Make any kselftest test module (using the kselftest_module framework)
> taint the kernel with TAINT_TEST on module load.
>
> Also mark the module as a test module using MODULE_INFO(test, "Y") so
> that other tools can tell this is a test module. We can't rely solely
> on this, though, as these test modules are also often built-in.
>
> Finally, update the kselftest documentation to mention that the kernel
> should be tainted, and how to do so manually (as below).
>
> 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")
>
> 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.
>
> Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
> Signed-off-by: David Gow <davidgow@...gle.com>
> ---

Whoops: forgot the changelogs. Only patches 2 and 4 had changes. For this patch:

Changes since v4:
https://lore.kernel.org/lkml/20220513083212.3537869-3-davidgow@google.com/
- Actually use the new TAINT_TEST name, instead of TAINT_KUNIT
(Thanks, kernel-test-robot)
- Document how to use this (or MODULE_INFO()) to taint the kernel.
(Thanks, Luis)
- Also add MODULE_INFO(test, "Y") to embed the fact that this is a
test module into the .ko
  - Nothing depends on it now, but it should allow us to tell this is
a test module without executing it in the future.

No changes since v3:
https://lore.kernel.org/lkml/20220513083212.3537869-3-davidgow@google.com/

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