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    Subject[PATCH 08/11] kasan: adopt kmalloc_uaf2 test to HW_TAGS mode
    From
    In the kmalloc_uaf2() test, the pointers to the two allocated memory
    blocks might be the same, and the test will fail. With the software
    tag-based mode, the probability of the that happening is 1/254, so it's
    hard to observe the failure. For the hardware tag-based mode though,
    the probablity is 1/14, which is quite noticable.

    Allow up to 4 attempts at generating different tags for the tag-based
    modes.

    Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
    Link: https://linux-review.googlesource.com/id/Ibfa458ef2804ff465d8eb07434a300bf36388d55
    ---
    lib/test_kasan.c | 9 +++++++++
    1 file changed, 9 insertions(+)

    diff --git a/lib/test_kasan.c b/lib/test_kasan.c
    index b5077a47b95a..b67da7f6e17f 100644
    --- a/lib/test_kasan.c
    +++ b/lib/test_kasan.c
    @@ -375,7 +375,9 @@ static void kmalloc_uaf2(struct kunit *test)
    {
    char *ptr1, *ptr2;
    size_t size = 43;
    + int counter = 0;

    +again:
    ptr1 = kmalloc(size, GFP_KERNEL);
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr1);

    @@ -384,6 +386,13 @@ static void kmalloc_uaf2(struct kunit *test)
    ptr2 = kmalloc(size, GFP_KERNEL);
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);

    + /*
    + * For tag-based KASAN ptr1 and ptr2 tags might happen to be the same.
    + * Allow up to 4 attempts at generating different tags.
    + */
    + if (!IS_ENABLED(CONFIG_KASAN_GENERIC) && ptr1 == ptr2 && counter++ < 4)
    + goto again;
    +
    KUNIT_EXPECT_KASAN_FAIL(test, ptr1[40] = 'x');
    KUNIT_EXPECT_PTR_NE(test, ptr1, ptr2);

    --
    2.29.2.729.g45daf8777d-goog
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