linux-kernel - Re: [PATCH 07/11] kasan: add compiler barriers to KUNIT_EXPECT_KASAN

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Message-ID: <X/2lcAQE4ia21uRj@elver.google.com>
Date:   Tue, 12 Jan 2021 14:34:40 +0100
From:   Marco Elver <elver@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will.deacon@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        kasan-dev@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/11] kasan: add compiler barriers to
 KUNIT_EXPECT_KASAN_FAIL

On Tue, Jan 05, 2021 at 07:27PM +0100, Andrey Konovalov wrote:
> It might not be obvious to the compiler that the expression must be
> executed between writing and reading to fail_data. In this case, the
> compiler might reorder or optimize away some of the accesses, and
> the tests will fail.
> 
> Add compiler barriers around the expression in KUNIT_EXPECT_KASAN_FAIL.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> Link: https://linux-review.googlesource.com/id/I046079f48641a1d36fe627fc8827a9249102fd50

Reviewed-by: Marco Elver <elver@...gle.com>

> ---
>  lib/test_kasan.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index dd3d2f95c24e..b5077a47b95a 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -79,7 +79,9 @@ static void kasan_test_exit(struct kunit *test)
>  				NULL,				\
>  				&resource,			\
>  				"kasan_data", &fail_data);	\
> +	barrier();						\
>  	expression;						\
> +	barrier();						\
>  	KUNIT_EXPECT_EQ(test,					\
>  			fail_data.report_expected,		\
>  			fail_data.report_found);		\
> -- 
> 2.29.2.729.g45daf8777d-goog
>