linux-kernel - Re: [RFC PATCH 1/2] Port KASAN Tests to KUnit

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Message-ID: <CAGXu5jKbpbH4sm4sv-74iHa+VzWuvF5v3ci7R-KVt+StRpMESg@mail.gmail.com>
Date:   Mon, 2 Mar 2020 09:52:25 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Patricia Alfonso <trishalfonso@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        David Gow <davidgow@...gle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>, kunit-dev@...glegroups.com
Subject: Re: [RFC PATCH 1/2] Port KASAN Tests to KUnit

On Sat, Feb 29, 2020 at 10:39 PM Dmitry Vyukov <dvyukov@...gle.com> wrote:
>
> On Sat, Feb 29, 2020 at 2:56 AM Patricia Alfonso
> <trishalfonso@...gle.com> wrote:
> > On Thu, Feb 27, 2020 at 6:19 AM Dmitry Vyukov <dvyukov@...gle.com> wrote:
> > >
> > > .On Thu, Feb 27, 2020 at 3:44 AM Patricia Alfonso
> > > > -       pr_info("out-of-bounds in copy_from_user()\n");
> > > > -       unused = copy_from_user(kmem, usermem, size + 1);
> > >
> > > Why is all of this removed?
> > > Most of these tests are hard earned and test some special corner cases.
> > >
> > I just moved it inside IS_MODULE(CONFIG_TEST_KASAN) instead because I
> > don't think there is a way to rewrite this without it being a module.
>
> You mean these are unconditionally crashing the machine? If yes,
> please add a comment about this.
>
> Theoretically we could have a notion of "death tests" similar to gunit:
> https://stackoverflow.com/questions/3698718/what-are-google-test-death-tests
> KUnit test runner wrapper would need to spawn a separete process per
> each such test. Under non-KUnit test runner these should probably be
> disabled by default and only run if specifically requested (a-la
> --gunit_filter/--gunit_also_run_disabled_tests).
> Could also be used to test other things that unconditionally panic,
> e.g. +Kees may be happy for unit tests for some of the
> hardening/fortification features.
> I am not asking to bundle this with this change of course.

A bunch of LKDTM tests can kill the system too. I collected the list
when building the selftest script for LKDTM:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/selftests/lkdtm/tests.txt

I'm all for unittests (I have earlier kind-of-unit-tests in
lib/test_user_copy.c lib/test_overflow.c etc), but most of LKDTM is
designed to be full system-behavior testing ("does the system correct
BUG the current thread, when some deeper system state is violated?")

-- 
Kees Cook