2022-09-24 20:26:46

by andrey.konovalov

Subject: [PATCH mm v2] 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 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 | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 71cb402c404f..dbb0a672380f 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -333,6 +333,8 @@ static void krealloc_more_oob_helper(struct kunit *test,
ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);

+ OPTIMIZER_HIDE_VAR(ptr2);
+
/* All offsets up to size2 must be accessible. */
ptr2[size1 - 1] = 'x';
ptr2[size1] = 'x';
@@ -365,6 +367,8 @@ static void krealloc_less_oob_helper(struct kunit *test,
ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);

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

@@ -578,13 +582,14 @@ 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

2022-09-25 17:17:40

by Andrew Morton

Subject: Re: [PATCH mm v2] kasan: fix array-bounds warnings in tests

On Sat, 24 Sep 2022 22:23:21 +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.
>
> ...
>
> --- a/mm/kasan/kasan_test.c
> +++ b/mm/kasan/kasan_test.c
> @@ -333,6 +333,8 @@ static void krealloc_more_oob_helper(struct kunit *test,
> ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
>
> + OPTIMIZER_HIDE_VAR(ptr2);
> +
> /* All offsets up to size2 must be accessible. */
> ptr2[size1 - 1] = 'x';
> ptr2[size1] = 'x';
> @@ -365,6 +367,8 @@ static void krealloc_less_oob_helper(struct kunit *test,
> ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
>
> + OPTIMIZER_HIDE_VAR(ptr2);

What chance does a reader have of working out why this is here? If
"little" then a code comment would be a nice way of saving that poor
person for having to dive into the git history.


> /* Must be accessible for all modes. */
> ptr2[size2 - 1] = 'x';
>
> @@ -578,13 +582,14 @@ 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 18:33:13

by Andrey Konovalov

Subject: Re: [PATCH mm v2] kasan: fix array-bounds warnings in tests

On Sun, Sep 25, 2022 at 7:03 PM Andrew Morton <[email protected]> wrote:
>
> > --- a/mm/kasan/kasan_test.c
> > +++ b/mm/kasan/kasan_test.c
> > @@ -333,6 +333,8 @@ static void krealloc_more_oob_helper(struct kunit *test,
> > ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
> > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
> >
> > + OPTIMIZER_HIDE_VAR(ptr2);
> > +
> > /* All offsets up to size2 must be accessible. */
> > ptr2[size1 - 1] = 'x';
> > ptr2[size1] = 'x';
> > @@ -365,6 +367,8 @@ static void krealloc_less_oob_helper(struct kunit *test,
> > ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
> > KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
> >
> > + OPTIMIZER_HIDE_VAR(ptr2);
>
> What chance does a reader have of working out why this is here? If
> "little" then a code comment would be a nice way of saving that poor
> person for having to dive into the git history.

Will add in v3. Thank you, Andrew!