Re: [PATCH] kasan: Enable KUnit integration whenever CONFIG_KUNIT is enabled

[David Gow <davidgow@google.com>]

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On Wed, Oct 19, 2022 at 10:18 PM Andrey Konovalov <andreyknvl@gmail.com> wrote:
>
> On Wed, Oct 19, 2022 at 10:58 AM 'David Gow' via kasan-dev
> <kasan-dev@googlegroups.com> wrote:
> >
> > Enable the KASAN/KUnit integration even when the KASAN tests are
> > disabled, as it's useful for testing other things under KASAN.
> > Essentially, this reverts commit 49d9977ac909 ("kasan: check CONFIG_KASAN_KUNIT_TEST instead of CONFIG_KUNIT").
> >
> > To mitigate the performance impact slightly, add a likely() to the check
> > for a currently running test.
> >
> > There's more we can do for performance if/when it becomes more of a
> > problem, such as only enabling the "expect a KASAN failure" support wif
> > the KASAN tests are enabled, or putting the whole thing behind a "kunit
> > tests are running" static branch (which I do plan to do eventually).
> >
> > Fixes: 49d9977ac909 ("kasan: check CONFIG_KASAN_KUNIT_TEST instead of CONFIG_KUNIT")
> > Signed-off-by: David Gow <davidgow@google.com>
> > ---
> >
> > Basically, hiding the KASAN/KUnit integration broke being able to just
> > pass --kconfig_add CONFIG_KASAN=y to kunit_tool to enable KASAN
> > integration. We didn't notice this, because usually
> > CONFIG_KUNIT_ALL_TESTS is enabled, which in turn enables
> > CONFIG_KASAN_KUNIT_TEST. However, using a separate .kunitconfig might
> > result in failures being missed.
> >
> > Take, for example:
> > ./tools/testing/kunit/kunit.py run --kconfig_add CONFIG_KASAN=y \
> >         --kunitconfig drivers/gpu/drm/tests
> >
> > This should run the drm tests with KASAN enabled, but even if there's a
> > KASAN failure (such as the one fixed by [1]), kunit_tool will report
> > success.
>
> Hi David,
>
> How does KUnit detect a KASAN failure for other tests than the KASAN
> ones? I thought this was only implemented for KASAN tests. At least, I
> don't see any code querying kunit_kasan_status outside of KASAN tests.

Yeah, there aren't any other tests which set up a "kasan_status"
resource to expect specific failures, but we still want the fallback
call to kunit_set_failure() so that any test which causes a KASAN
report will fail:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/kasan/report.c#n130

> I'm currently switching KASAN tests from using KUnit resources to
> console tracepoints [1], and those patches will be in conflict with
> yours.

Ah, sorry -- I'd seen these go past, and totally forgot about them! I
think all we really want to keep is the ability to fail tests if a
KASAN report occurs. The tricky bit is then disabling that for the
KASAN tests, so that they can have "expected" failures.

-- David

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