linux-kernel - Re: [RFC PATCH 2/2] KUnit: KASAN Integration

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Date:   Sun, 1 Mar 2020 07:29:07 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Patricia Alfonso <trishalfonso@...gle.com>
Cc:     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 2/2] KUnit: KASAN Integration

On Sat, Feb 29, 2020 at 2:23 AM Patricia Alfonso
<trishalfonso@...gle.com> wrote:
> >
> > On Thu, Feb 27, 2020 at 3:44 AM 'Patricia Alfonso' via kasan-dev
> > <kasan-dev@...glegroups.com> wrote:
> > >
> > > Integrate KASAN into KUnit testing framework.
> > >  - Fail tests when KASAN reports an error that is not expected
> > >  - Use KUNIT_EXPECT_KASAN_FAIL to expect a KASAN error in KASAN tests
> > >  - KUnit struct added to current task to keep track of the current test
> > > from KASAN code
> > >  - Booleans representing if a KASAN report is expected and if a KASAN
> > >  report is found added to kunit struct
> > >  - This prints "line# has passed" or "line# has failed"
> > >
> > > Signed-off-by: Patricia Alfonso <trishalfonso@...gle.com>
> > > ---
> > > If anyone has any suggestions on how best to print the failure
> > > messages, please share!
> > >
> > > One issue I have found while testing this is the allocation fails in
> > > kmalloc_pagealloc_oob_right() sometimes, but not consistently. This
> > > does cause the test to fail on the KUnit side, as expected, but it
> > > seems to skip all the tests before this one because the output starts
> > > with this failure instead of with the first test, kmalloc_oob_right().
> >
> > I don't follow this... we don't check output in any way, so how does
> > output affect execution?...
> >
> I'm sorry. I think I was just reading the results wrong before - no
> wonder I was confused!
>
> I just recreated the error and it does work as expected.
>
> >
> > > --- a/tools/testing/kunit/kunit_kernel.py
> > > +++ b/tools/testing/kunit/kunit_kernel.py
> > > @@ -141,7 +141,7 @@ class LinuxSourceTree(object):
> > >                 return True
> > >
> > >         def run_kernel(self, args=[], timeout=None, build_dir=''):
> > > -               args.extend(['mem=256M'])
> > > +               args.extend(['mem=256M', 'kasan_multi_shot'])
> >
> > This is better done somewhere else (different default value if
> > KASAN_TEST is enabled or something). Or overridden in the KASAN tests.
> > Not everybody uses tools/testing/kunit/kunit_kernel.py and this seems
> > to be a mandatory part now. This means people will always hit this, be
> > confused, figure out they need to flip the value, and only then be
> > able to run kunit+kasan.
> >
> I agree. Is the best way to do this with "bool multishot =
> kasan_save_enable_multi_shot();"  and
> "kasan_restore_multi_shot(multishot);" inside test_kasan.c like what
> was done in the tests before?

This will fix KASAN tests, but not non-KASAN tests running under KUNIT
and triggering KASAN reports.
You set kasan_multi_shot for all KUNIT tests. I am reading this as
that we don't want to abort on the first test that triggered a KASAN
report. Or not?