Date:   Fri, 8 Jul 2022 12:54:26 +0800
From:   David Gow <davidgow@...gle.com>
To:     Nathan Chancellor <nathan@...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>,
        Luis Chamberlain <mcgrof@...nel.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 v5 2/4] module: panic: Taint the kernel when selftest
 modules load

On Fri, Jul 8, 2022 at 8:40 AM Nathan Chancellor <nathan@...nel.org> wrote:
>
> On Sat, Jul 02, 2022 at 12:09:57PM +0800, David Gow wrote:
> > Taint the kernel with TAINT_TEST whenever a test module loads, by adding
> > a new "TEST" module property, and setting it for all modules in the
> > tools/testing directory. This property can also be set manually, for
> > tests which live outside the tools/testing directory with:
> > MODULE_INFO(test, "Y");
> >
> > Reviewed-by: Luis Chamberlain <mcgrof@...nel.org>
> > Signed-off-by: David Gow <davidgow@...gle.com>
> > ---
> >  kernel/module/main.c  | 7 +++++++
> >  scripts/mod/modpost.c | 3 +++
> >  2 files changed, 10 insertions(+)
> >
> > diff --git a/kernel/module/main.c b/kernel/module/main.c
> > index fed58d30725d..730503561eb0 100644
> > --- a/kernel/module/main.c
> > +++ b/kernel/module/main.c
> > @@ -1988,6 +1988,13 @@ static int check_modinfo(struct module *mod, struct load_info *info, int flags)
> >       /* Set up license info based on the info section */
> >       set_license(mod, get_modinfo(info, "license"));
> >
> > +     if (!get_modinfo(info, "test")) {
> > +             if (!test_taint(TAINT_TEST))
> > +                     pr_warn_once("%s: loading test module taints kernel.\n",
> > +                                  mod->name);
> > +             add_taint_module(mod, TAINT_TEST, LOCKDEP_STILL_OK);
> > +     }
> > +
> >       return 0;
> >  }
> >
> > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> > index 29d5a841e215..5937212b4433 100644
> > --- a/scripts/mod/modpost.c
> > +++ b/scripts/mod/modpost.c
> > @@ -2191,6 +2191,9 @@ static void add_header(struct buffer *b, struct module *mod)
> >
> >       if (strstarts(mod->name, "drivers/staging"))
> >               buf_printf(b, "\nMODULE_INFO(staging, \"Y\");\n");
> > +
> > +     if (strstarts(mod->name, "tools/testing"))
> > +             buf_printf(b, "\nMODULE_INFO(test, \"Y\");\n");
> >  }
> >
> >  static void add_exported_symbols(struct buffer *buf, struct module *mod)
> > --
> > 2.37.0.rc0.161.g10f37bed90-goog
> >
> >
>
> Hi David,
>
> This change has landed in linux-next as commit e20729ede7ed ("module:
> panic: taint the kernel when selftest modules load") and on all of my
> test machines, I see this new message printed, even though as far as I
> am aware, I am not loading any testing modules. For example, in QEMU, I
> see:
>
> [    0.596978] serio: loading test module taints kernel.
>
> and on my Honeycomb LX2, I see:
>
> [    5.400861] fuse: loading test module taints kernel.
>
> It seems like the get_modinfo() check might be wrong? The following diff
> resolves it for me, I can send a formal patch if necessary (although it
> appears to have gone in via -mm so I assume Andrew can squash this in).
>

Whoops: this is definitely the wrong way round. Thanks very much for
catching it! (I'd swapped it locally at some point to test, and
must've accidentally committed it.)

I've sent out v6 with this fixed (and a couple of other minor changes):
https://lore.kernel.org/linux-kselftest/20220708044847.531566-2-davidgow@google.com/T/#u

That being said, if just squashing your change below in is easier, I'm
fine with that, too. (The other changes are minor enough that we could
live without them and/or send them in separately.)

Unless there are any objections, should Andrew update this patch in
his tree, and we remove the series from the kunit tree?

Cheers,
-- David

>
> diff --git a/kernel/module/main.c b/kernel/module/main.c
> index 730503561eb0..4f91e41b8bc9 100644
> --- a/kernel/module/main.c
> +++ b/kernel/module/main.c
> @@ -1988,7 +1988,7 @@ static int check_modinfo(struct module *mod, struct load_info *info, int flags)
>         /* Set up license info based on the info section */
>         set_license(mod, get_modinfo(info, "license"));
>
> -       if (!get_modinfo(info, "test")) {
> +       if (get_modinfo(info, "test")) {
>                 if (!test_taint(TAINT_TEST))
>                         pr_warn_once("%s: loading test module taints kernel.\n",
>                                      mod->name);

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