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    Subject[PATCH v3 03/15] kasan: clean up comments in tests
    From
    Clarify and update comments in KASAN tests.

    Link: https://linux-review.googlesource.com/id/I6c816c51fa1e0eb7aa3dead6bda1f339d2af46c8
    Reviewed-by: Marco Elver <elver@google.com>
    Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
    ---
    lib/test_kasan.c | 59 +++++++++++++++++++++++++----------------
    lib/test_kasan_module.c | 5 ++--
    2 files changed, 39 insertions(+), 25 deletions(-)

    diff --git a/lib/test_kasan.c b/lib/test_kasan.c
    index 2947274cc2d3..6f46e27c2af7 100644
    --- a/lib/test_kasan.c
    +++ b/lib/test_kasan.c
    @@ -28,10 +28,9 @@
    #define OOB_TAG_OFF (IS_ENABLED(CONFIG_KASAN_GENERIC) ? 0 : KASAN_GRANULE_SIZE)

    /*
    - * We assign some test results to these globals to make sure the tests
    - * are not eliminated as dead code.
    + * Some tests use these global variables to store return values from function
    + * calls that could otherwise be eliminated by the compiler as dead code.
    */
    -
    void *kasan_ptr_result;
    int kasan_int_result;

    @@ -39,14 +38,13 @@ static struct kunit_resource resource;
    static struct kunit_kasan_expectation fail_data;
    static bool multishot;

    +/*
    + * Temporarily enable multi-shot mode. Otherwise, KASAN would only report the
    + * first detected bug and panic the kernel if panic_on_warn is enabled.
    + */
    static int kasan_test_init(struct kunit *test)
    {
    - /*
    - * Temporarily enable multi-shot mode and set panic_on_warn=0.
    - * Otherwise, we'd only get a report for the first case.
    - */
    multishot = kasan_save_enable_multi_shot();
    -
    return 0;
    }

    @@ -56,12 +54,12 @@ static void kasan_test_exit(struct kunit *test)
    }

    /**
    - * KUNIT_EXPECT_KASAN_FAIL() - Causes a test failure when the expression does
    - * not cause a KASAN error. This uses a KUnit resource named "kasan_data." Do
    - * Do not use this name for a KUnit resource outside here.
    - *
    + * KUNIT_EXPECT_KASAN_FAIL() - check that the executed expression produces a
    + * KASAN report; causes a test failure otherwise. This relies on a KUnit
    + * resource named "kasan_data". Do not use this name for KUnit resources
    + * outside of KASAN tests.
    */
    -#define KUNIT_EXPECT_KASAN_FAIL(test, condition) do { \
    +#define KUNIT_EXPECT_KASAN_FAIL(test, expression) do { \
    fail_data.report_expected = true; \
    fail_data.report_found = false; \
    kunit_add_named_resource(test, \
    @@ -69,7 +67,7 @@ static void kasan_test_exit(struct kunit *test)
    NULL, \
    &resource, \
    "kasan_data", &fail_data); \
    - condition; \
    + expression; \
    KUNIT_EXPECT_EQ(test, \
    fail_data.report_expected, \
    fail_data.report_found); \
    @@ -121,7 +119,8 @@ static void kmalloc_pagealloc_oob_right(struct kunit *test)
    return;
    }

    - /* Allocate a chunk that does not fit into a SLUB cache to trigger
    + /*
    + * Allocate a chunk that does not fit into a SLUB cache to trigger
    * the page allocator fallback.
    */
    ptr = kmalloc(size, GFP_KERNEL);
    @@ -168,7 +167,9 @@ static void kmalloc_large_oob_right(struct kunit *test)
    {
    char *ptr;
    size_t size = KMALLOC_MAX_CACHE_SIZE - 256;
    - /* Allocate a chunk that is large enough, but still fits into a slab
    +
    + /*
    + * Allocate a chunk that is large enough, but still fits into a slab
    * and does not trigger the page allocator fallback in SLUB.
    */
    ptr = kmalloc(size, GFP_KERNEL);
    @@ -469,10 +470,13 @@ static void ksize_unpoisons_memory(struct kunit *test)
    ptr = kmalloc(size, GFP_KERNEL);
    KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
    real_size = ksize(ptr);
    - /* This access doesn't trigger an error. */
    +
    + /* This access shouldn't trigger a KASAN report. */
    ptr[size] = 'x';
    - /* This one does. */
    +
    + /* This one must. */
    KUNIT_EXPECT_KASAN_FAIL(test, ptr[real_size] = 'y');
    +
    kfree(ptr);
    }

    @@ -568,7 +572,7 @@ static void kmem_cache_invalid_free(struct kunit *test)
    return;
    }

    - /* Trigger invalid free, the object doesn't get freed */
    + /* Trigger invalid free, the object doesn't get freed. */
    KUNIT_EXPECT_KASAN_FAIL(test, kmem_cache_free(cache, p + 1));

    /*
    @@ -585,7 +589,10 @@ static void kasan_memchr(struct kunit *test)
    char *ptr;
    size_t size = 24;

    - /* See https://bugzilla.kernel.org/show_bug.cgi?id=206337 */
    + /*
    + * str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT.
    + * See https://bugzilla.kernel.org/show_bug.cgi?id=206337 for details.
    + */
    if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
    kunit_info(test,
    "str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT");
    @@ -610,7 +617,10 @@ static void kasan_memcmp(struct kunit *test)
    size_t size = 24;
    int arr[9];

    - /* See https://bugzilla.kernel.org/show_bug.cgi?id=206337 */
    + /*
    + * str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT.
    + * See https://bugzilla.kernel.org/show_bug.cgi?id=206337 for details.
    + */
    if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
    kunit_info(test,
    "str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT");
    @@ -634,7 +644,10 @@ static void kasan_strings(struct kunit *test)
    char *ptr;
    size_t size = 24;

    - /* See https://bugzilla.kernel.org/show_bug.cgi?id=206337 */
    + /*
    + * str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT.
    + * See https://bugzilla.kernel.org/show_bug.cgi?id=206337 for details.
    + */
    if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
    kunit_info(test,
    "str* functions are not instrumented with CONFIG_AMD_MEM_ENCRYPT");
    @@ -706,7 +719,7 @@ static void kasan_bitops_generic(struct kunit *test)
    }

    /*
    - * Allocate 1 more byte, which causes kzalloc to round up to 16-bytes;
    + * Allocate 1 more byte, which causes kzalloc to round up to 16 bytes;
    * this way we do not actually corrupt other memory.
    */
    bits = kzalloc(sizeof(*bits) + 1, GFP_KERNEL);
    diff --git a/lib/test_kasan_module.c b/lib/test_kasan_module.c
    index 3b4cc77992d2..eee017ff8980 100644
    --- a/lib/test_kasan_module.c
    +++ b/lib/test_kasan_module.c
    @@ -123,8 +123,9 @@ static noinline void __init kasan_workqueue_uaf(void)
    static int __init test_kasan_module_init(void)
    {
    /*
    - * Temporarily enable multi-shot mode. Otherwise, we'd only get a
    - * report for the first case.
    + * Temporarily enable multi-shot mode. Otherwise, KASAN would only
    + * report the first detected bug and panic the kernel if panic_on_warn
    + * is enabled.
    */
    bool multishot = kasan_save_enable_multi_shot();

    --
    2.30.0.284.gd98b1dd5eaa7-goog
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