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Date:   Tue,  5 Jan 2021 19:27:51 +0100
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Subject: [PATCH 07/11] kasan: add compiler barriers to KUNIT_EXPECT_KASAN_FAIL
From:   Andrey Konovalov <andreyknvl@google.com>
To:     Catalin Marinas <catalin.marinas@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Will Deacon <will.deacon@arm.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>
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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@google.com>
Link: https://linux-review.googlesource.com/id/I046079f48641a1d36fe627fc8827a9249102fd50
---
 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