On Wed, 17 Nov 2021 at 13:59, Andrey Konovalov <andreyknvl@xxxxxxxxx> wrote:
>
> 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.
I was wondering how to solve the cyclic dependency, because I wanted
to link this patch from the bugzilla.
Now that the bugzilla entry exists, I guess I can add it and then
update bugzilla with link to this patch closing the cycle. :-)
> > + 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!
>
> --
> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@xxxxxxxxxxxxxxxx.
> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/CA%2BfCnZcp3dFd3rwpLx6VUi2Yv9uqsWQyQNB6d3X-A7VgTjXUpw%40mail.gmail.com.
