On Wed, Nov 17, 2021 at 12:09 PM Marco Elver <elver@xxxxxxxxxx> wrote:
>
> Add a test checking that KASAN generic can also detect out-of-bounds
> accesses to the left of globals.
>
> Unfortunately it seems that GCC doesn't catch this (tested GCC 10, 11).
> The main difference between GCC's globals redzoning and Clang's is that
> GCC relies on using increased alignment to producing padding, where
> Clang's redzoning implementation actually adds real data after the
> global and doesn't rely on alignment to produce padding. I believe this
> is the main reason why GCC can't reliably catch globals out-of-bounds in
> this case.
>
> Given this is now a known issue, to avoid failing the whole test suite,
> skip this test case with GCC.
>
> Reported-by: Kaiwan N Billimoria <kaiwan.billimoria@xxxxxxxxx>
> Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Hi Marco,
> ---
> lib/test_kasan.c | 18 ++++++++++++++++--
> 1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 67ed689a0b1b..69c32c91420b 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -700,7 +700,7 @@ static void kmem_cache_bulk(struct kunit *test)
>
> static char global_array[10];
>
> -static void kasan_global_oob(struct kunit *test)
> +static void kasan_global_oob_right(struct kunit *test)
> {
> /*
> * Deliberate out-of-bounds access. To prevent CONFIG_UBSAN_LOCAL_BOUNDS
> @@ -723,6 +723,19 @@ static void kasan_global_oob(struct kunit *test)
> KUNIT_EXPECT_KASAN_FAIL(test, *(volatile char *)p);
> }
>
> +static void kasan_global_oob_left(struct kunit *test)
> +{
> + char *volatile array = global_array;
> + char *p = array - 3;
> +
> + /*
> + * GCC is known to fail this test, skip it.
> + */
Please link the KASAN bugzilla issue here.
> + KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_CC_IS_CLANG);
> + KASAN_TEST_NEEDS_CONFIG_ON(test, CONFIG_KASAN_GENERIC);
> + KUNIT_EXPECT_KASAN_FAIL(test, *(volatile char *)p);
> +}
> +
> /* Check that ksize() makes the whole object accessible. */
> static void ksize_unpoisons_memory(struct kunit *test)
> {
> @@ -1160,7 +1173,8 @@ static struct kunit_case kasan_kunit_test_cases[] = {
> KUNIT_CASE(kmem_cache_oob),
> KUNIT_CASE(kmem_cache_accounted),
> KUNIT_CASE(kmem_cache_bulk),
> - KUNIT_CASE(kasan_global_oob),
> + KUNIT_CASE(kasan_global_oob_right),
> + KUNIT_CASE(kasan_global_oob_left),
> KUNIT_CASE(kasan_stack_oob),
> KUNIT_CASE(kasan_alloca_oob_left),
> KUNIT_CASE(kasan_alloca_oob_right),
> --
> 2.34.0.rc2.393.gf8c9666880-goog
>
Otherwise:
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Thanks!
