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    Subject[PATCH 5.18 0180/1095] kasan: test: Silence GCC 12 warnings
    Date
    From: Kees Cook <keescook@chromium.org>

    [ Upstream commit aaf50b1969d7933a51ea421b11432a7fb90974e3 ]

    GCC 12 continues to get smarter about array accesses. The KASAN tests
    are expecting to explicitly test out-of-bounds conditions at run-time,
    so hide the variable from GCC, to avoid warnings like:

    ../lib/test_kasan.c: In function 'ksize_uaf':
    ../lib/test_kasan.c:790:61: warning: array subscript 120 is outside array bounds of 'void[120]' [-Warray-bounds]
    790 | KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[size]);
    | ~~~~~~~~~~~~~~~~~~~~~~^~~~~~
    ../lib/test_kasan.c:97:9: note: in definition of macro 'KUNIT_EXPECT_KASAN_FAIL'
    97 | expression; \
    | ^~~~~~~~~~

    Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
    Cc: Alexander Potapenko <glider@google.com>
    Cc: Andrey Konovalov <andreyknvl@gmail.com>
    Cc: Dmitry Vyukov <dvyukov@google.com>
    Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
    Cc: kasan-dev@googlegroups.com
    Signed-off-by: Kees Cook <keescook@chromium.org>
    Link: https://lore.kernel.org/r/20220608214024.1068451-1-keescook@chromium.org
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    lib/test_kasan.c | 10 ++++++++++
    1 file changed, 10 insertions(+)

    diff --git a/lib/test_kasan.c b/lib/test_kasan.c
    index ad880231dfa8..630e0c31d7c2 100644
    --- a/lib/test_kasan.c
    +++ b/lib/test_kasan.c
    @@ -131,6 +131,7 @@ static void kmalloc_oob_right(struct kunit *test)
    ptr = kmalloc(size, GFP_KERNEL);
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

    + OPTIMIZER_HIDE_VAR(ptr);
    /*
    * An unaligned access past the requested kmalloc size.
    * Only generic KASAN can precisely detect these.
    @@ -159,6 +160,7 @@ static void kmalloc_oob_left(struct kunit *test)
    ptr = kmalloc(size, GFP_KERNEL);
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

    + OPTIMIZER_HIDE_VAR(ptr);
    KUNIT_EXPECT_KASAN_FAIL(test, *ptr = *(ptr - 1));
    kfree(ptr);
    }
    @@ -171,6 +173,7 @@ static void kmalloc_node_oob_right(struct kunit *test)
    ptr = kmalloc_node(size, GFP_KERNEL, 0);
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

    + OPTIMIZER_HIDE_VAR(ptr);
    KUNIT_EXPECT_KASAN_FAIL(test, ptr[0] = ptr[size]);
    kfree(ptr);
    }
    @@ -191,6 +194,7 @@ static void kmalloc_pagealloc_oob_right(struct kunit *test)
    ptr = kmalloc(size, GFP_KERNEL);
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

    + OPTIMIZER_HIDE_VAR(ptr);
    KUNIT_EXPECT_KASAN_FAIL(test, ptr[size + OOB_TAG_OFF] = 0);

    kfree(ptr);
    @@ -271,6 +275,7 @@ static void kmalloc_large_oob_right(struct kunit *test)
    ptr = kmalloc(size, GFP_KERNEL);
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

    + OPTIMIZER_HIDE_VAR(ptr);
    KUNIT_EXPECT_KASAN_FAIL(test, ptr[size] = 0);
    kfree(ptr);
    }
    @@ -410,6 +415,8 @@ static void kmalloc_oob_16(struct kunit *test)
    ptr2 = kmalloc(sizeof(*ptr2), GFP_KERNEL);
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);

    + OPTIMIZER_HIDE_VAR(ptr1);
    + OPTIMIZER_HIDE_VAR(ptr2);
    KUNIT_EXPECT_KASAN_FAIL(test, *ptr1 = *ptr2);
    kfree(ptr1);
    kfree(ptr2);
    @@ -756,6 +763,8 @@ static void ksize_unpoisons_memory(struct kunit *test)
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
    real_size = ksize(ptr);

    + OPTIMIZER_HIDE_VAR(ptr);
    +
    /* This access shouldn't trigger a KASAN report. */
    ptr[size] = 'x';

    @@ -778,6 +787,7 @@ static void ksize_uaf(struct kunit *test)
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
    kfree(ptr);

    + OPTIMIZER_HIDE_VAR(ptr);
    KUNIT_EXPECT_KASAN_FAIL(test, ksize(ptr));
    KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[0]);
    KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[size]);
    --
    2.35.1


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