2022-09-26 19:04:20

by andrey.konovalov

Subject: [PATCH mm v3] kasan: fix array-bounds warnings in tests

From: Andrey Konovalov <[email protected]>

GCC's -Warray-bounds option detects out-of-bounds accesses to
statically-sized allocations in krealloc out-of-bounds tests.

Use OPTIMIZER_HIDE_VAR to suppress the warning.

Also change kmalloc_memmove_invalid_size to use OPTIMIZER_HIDE_VAR
instead of a volatile variable.

Reported-by: kernel test robot <[email protected]>
Signed-off-by: Andrey Konovalov <[email protected]>

---

Changes v2->v3:
- Add comment for added -Warray-bounds-related OPTIMIZER_HIDE_VAR.

Changes v1->v2:
- Hide ptr2 instead of size1 and size2 to be consistent with other
uses of OPTIMIZER_HIDE_VAR in KASAN tests.
---
mm/kasan/kasan_test.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 71cb402c404f..f50b11d84f41 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -333,6 +333,9 @@ static void krealloc_more_oob_helper(struct kunit *test,
ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);

+ /* Suppress -Warray-bounds warnings. */
+ OPTIMIZER_HIDE_VAR(ptr2);
+
/* All offsets up to size2 must be accessible. */
ptr2[size1 - 1] = 'x';
ptr2[size1] = 'x';
@@ -365,6 +368,9 @@ static void krealloc_less_oob_helper(struct kunit *test,
ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);

+ /* Suppress -Warray-bounds warnings. */
+ OPTIMIZER_HIDE_VAR(ptr2);
+
/* Must be accessible for all modes. */
ptr2[size2 - 1] = 'x';

@@ -578,13 +584,14 @@ static void kmalloc_memmove_invalid_size(struct kunit *test)
{
char *ptr;
size_t size = 64;
- volatile size_t invalid_size = size;
+ size_t invalid_size = size;

ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

memset((char *)ptr, 0, 64);
OPTIMIZER_HIDE_VAR(ptr);
+ OPTIMIZER_HIDE_VAR(invalid_size);
KUNIT_EXPECT_KASAN_FAIL(test,
memmove((char *)ptr, (char *)ptr + 4, invalid_size));
kfree(ptr);
--
2.25.1

2022-09-26 19:04:48

by Kees Cook

Subject: Re: [PATCH mm v3] kasan: fix array-bounds warnings in tests

On Mon, Sep 26, 2022 at 08:08:47PM +0200, [email protected] wrote:
> From: Andrey Konovalov <[email protected]>
>
> GCC's -Warray-bounds option detects out-of-bounds accesses to
> statically-sized allocations in krealloc out-of-bounds tests.
>
> Use OPTIMIZER_HIDE_VAR to suppress the warning.
>
> Also change kmalloc_memmove_invalid_size to use OPTIMIZER_HIDE_VAR
> instead of a volatile variable.
>
> Reported-by: kernel test robot <[email protected]>
> Signed-off-by: Andrey Konovalov <[email protected]>

Reviewed-by: Kees Cook <[email protected]>

--
Kees Cook