[PATCH] kasan: test: Silence intentional read overflow warnings

[Kees Cook]

As done in commit d73dad4eb5ad ("kasan: test: bypass __alloc_size checks")
for __write_overflow warnings, also silence some more cases that trip
the __read_overflow warnings seen in 5.16-rc1[1]:

In file included from /kisskb/src/include/linux/string.h:253,
from /kisskb/src/include/linux/bitmap.h:10,
from /kisskb/src/include/linux/cpumask.h:12,
from /kisskb/src/include/linux/mm_types_task.h:14,
from /kisskb/src/include/linux/mm_types.h:5,
from /kisskb/src/include/linux/page-flags.h:13,
from /kisskb/src/arch/arm64/include/asm/mte.h:14,
from /kisskb/src/arch/arm64/include/asm/pgtable.h:12,
from /kisskb/src/include/linux/pgtable.h:6,
from /kisskb/src/include/linux/kasan.h:29,
from /kisskb/src/lib/test_kasan.c:10:
In function 'memcmp',
inlined from 'kasan_memcmp' at /kisskb/src/lib/test_kasan.c:897:2:
/kisskb/src/include/linux/fortify-string.h:263:25: error: call to '__read_overflow' declared with attribute error: detected read beyond size of object (1st parameter)
263 | __read_overflow();
| ^~~~~~~~~~~~~~~~~
In function 'memchr',
inlined from 'kasan_memchr' at /kisskb/src/lib/test_kasan.c:872:2:
/kisskb/src/include/linux/fortify-string.h:277:17: error: call to '__read_overflow' declared with attribute error: detected read beyond size of object (1st parameter)
277 | __read_overflow();
| ^~~~~~~~~~~~~~~~~

[1] http://kisskb.ellerman.id.au/kisskb/buildresult/14660585/log/

Cc: Marco Elver <el...@google.com>
Cc: Andrey Ryabinin <ryabin...@gmail.com>
Cc: Alexander Potapenko <gli...@google.com>
Cc: Andrey Konovalov <andre...@gmail.com>
Cc: Dmitry Vyukov <dvy...@google.com>
Cc: kasa...@googlegroups.com
Fixes: d73dad4eb5ad ("kasan: test: bypass __alloc_size checks")
Signed-off-by: Kees Cook <kees...@chromium.org>
---
lib/test_kasan.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 67ed689a0b1b..0643573f8686 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -869,6 +869,7 @@ static void kasan_memchr(struct kunit *test)
ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

+ OPTIMIZER_HIDE_VAR(size);
KUNIT_EXPECT_KASAN_FAIL(test,
kasan_ptr_result = memchr(ptr, '1', size + 1));

@@ -894,6 +895,7 @@ static void kasan_memcmp(struct kunit *test)
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
memset(arr, 0, sizeof(arr));

+ OPTIMIZER_HIDE_VAR(size);
KUNIT_EXPECT_KASAN_FAIL(test,
kasan_int_result = memcmp(ptr, arr, size+1));
kfree(ptr);
--
2.30.2

[Andrey Konovalov]

Reviewed-by: Andrey Konovalov <andre...@gmail.com>

Thanks!

[Marco Elver]

Acked-by: Marco Elver <el...@google.com>

Thanks for the quick fix!

> ---
> lib/test_kasan.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 67ed689a0b1b..0643573f8686 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -869,6 +869,7 @@ static void kasan_memchr(struct kunit *test)
> ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(size);
> KUNIT_EXPECT_KASAN_FAIL(test,
> kasan_ptr_result = memchr(ptr, '1', size + 1));
>
> @@ -894,6 +895,7 @@ static void kasan_memcmp(struct kunit *test)
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> memset(arr, 0, sizeof(arr));
>
> + OPTIMIZER_HIDE_VAR(size);
> KUNIT_EXPECT_KASAN_FAIL(test,
> kasan_int_result = memcmp(ptr, arr, size+1));
> kfree(ptr);
> --
> 2.30.2
>

> --
> 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+...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20211116004111.3171781-1-keescook%40chromium.org.