2023-12-14 16:44:46

by Nico Pache

Subject: [PATCH v2] kunit: kasan_test: disable fortify string checker on kmalloc_oob_memset

similar to commit 09c6304e38e4 ("kasan: test: fix compatibility with
FORTIFY_SOURCE") the kernel is panicing in kmalloc_oob_memset_*.

This is due to the `ptr` not being hidden from the optimizer which would
disable the runtime fortify string checker.

kernel BUG at lib/string_helpers.c:1048!
Call Trace:
[<00000000272502e2>] fortify_panic+0x2a/0x30
([<00000000272502de>] fortify_panic+0x26/0x30)
[<001bffff817045c4>] kmalloc_oob_memset_2+0x22c/0x230 [kasan_test]

Hide the `ptr` variable from the optimizer to fix the kernel panic.
Also define a memset_size variable and hide that as well. This cleans up
the code and follows the same convention as other tests.

Signed-off-by: Nico Pache <[email protected]>
---
mm/kasan/kasan_test.c | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 8281eb42464b..34515a106ca5 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -493,14 +493,17 @@ static void kmalloc_oob_memset_2(struct kunit *test)
{
char *ptr;
size_t size = 128 - KASAN_GRANULE_SIZE;
+ size_t memset_size = 2;

KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);

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

+ OPTIMIZER_HIDE_VAR(ptr);
OPTIMIZER_HIDE_VAR(size);
- KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, 2));
+ OPTIMIZER_HIDE_VAR(memset_size);
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, memset_size));
kfree(ptr);
}

@@ -508,14 +511,17 @@ static void kmalloc_oob_memset_4(struct kunit *test)
{
char *ptr;
size_t size = 128 - KASAN_GRANULE_SIZE;
+ size_t memset_size = 4;

KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);

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

+ OPTIMIZER_HIDE_VAR(ptr);
OPTIMIZER_HIDE_VAR(size);
- KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, 4));
+ OPTIMIZER_HIDE_VAR(memset_size);
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, memset_size));
kfree(ptr);
}

@@ -523,14 +529,17 @@ static void kmalloc_oob_memset_8(struct kunit *test)
{
char *ptr;
size_t size = 128 - KASAN_GRANULE_SIZE;
+ size_t memset_size = 8;

KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);

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

+ OPTIMIZER_HIDE_VAR(ptr);
OPTIMIZER_HIDE_VAR(size);
- KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, 8));
+ OPTIMIZER_HIDE_VAR(memset_size);
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, memset_size));
kfree(ptr);
}

@@ -538,14 +547,17 @@ static void kmalloc_oob_memset_16(struct kunit *test)
{
char *ptr;
size_t size = 128 - KASAN_GRANULE_SIZE;
+ size_t memset_size = 16;

KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);

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

+ OPTIMIZER_HIDE_VAR(ptr);
OPTIMIZER_HIDE_VAR(size);
- KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, 16));
+ OPTIMIZER_HIDE_VAR(memset_size);
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, memset_size));
kfree(ptr);
}

--
2.43.0

2023-12-14 21:25:54

by Andrey Konovalov

Subject: Re: [PATCH v2] kunit: kasan_test: disable fortify string checker on kmalloc_oob_memset

On Thu, Dec 14, 2023 at 5:44 PM Nico Pache <[email protected]> wrote:
>
> similar to commit 09c6304e38e4 ("kasan: test: fix compatibility with
> FORTIFY_SOURCE") the kernel is panicing in kmalloc_oob_memset_*.
>
> This is due to the `ptr` not being hidden from the optimizer which would
> disable the runtime fortify string checker.
>
> kernel BUG at lib/string_helpers.c:1048!
> Call Trace:
> [<00000000272502e2>] fortify_panic+0x2a/0x30
> ([<00000000272502de>] fortify_panic+0x26/0x30)
> [<001bffff817045c4>] kmalloc_oob_memset_2+0x22c/0x230 [kasan_test]
>
> Hide the `ptr` variable from the optimizer to fix the kernel panic.
> Also define a memset_size variable and hide that as well. This cleans up
> the code and follows the same convention as other tests.
>
> Signed-off-by: Nico Pache <[email protected]>
> ---
> mm/kasan/kasan_test.c | 20 ++++++++++++++++----
> 1 file changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
> index 8281eb42464b..34515a106ca5 100644
> --- a/mm/kasan/kasan_test.c
> +++ b/mm/kasan/kasan_test.c
> @@ -493,14 +493,17 @@ static void kmalloc_oob_memset_2(struct kunit *test)
> {
> char *ptr;
> size_t size = 128 - KASAN_GRANULE_SIZE;
> + size_t memset_size = 2;
>
> KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
>
> ptr = kmalloc(size, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> OPTIMIZER_HIDE_VAR(size);
> - KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, 2));
> + OPTIMIZER_HIDE_VAR(memset_size);
> + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, memset_size));
> kfree(ptr);
> }
>
> @@ -508,14 +511,17 @@ static void kmalloc_oob_memset_4(struct kunit *test)
> {
> char *ptr;
> size_t size = 128 - KASAN_GRANULE_SIZE;
> + size_t memset_size = 4;
>
> KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
>
> ptr = kmalloc(size, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> OPTIMIZER_HIDE_VAR(size);
> - KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, 4));
> + OPTIMIZER_HIDE_VAR(memset_size);
> + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, memset_size));
> kfree(ptr);
> }
>
> @@ -523,14 +529,17 @@ static void kmalloc_oob_memset_8(struct kunit *test)
> {
> char *ptr;
> size_t size = 128 - KASAN_GRANULE_SIZE;
> + size_t memset_size = 8;
>
> KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
>
> ptr = kmalloc(size, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> OPTIMIZER_HIDE_VAR(size);
> - KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, 8));
> + OPTIMIZER_HIDE_VAR(memset_size);
> + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, memset_size));
> kfree(ptr);
> }
>
> @@ -538,14 +547,17 @@ static void kmalloc_oob_memset_16(struct kunit *test)
> {
> char *ptr;
> size_t size = 128 - KASAN_GRANULE_SIZE;
> + size_t memset_size = 16;
>
> KASAN_TEST_NEEDS_CHECKED_MEMINTRINSICS(test);
>
> ptr = kmalloc(size, GFP_KERNEL);
> KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>
> + OPTIMIZER_HIDE_VAR(ptr);
> OPTIMIZER_HIDE_VAR(size);
> - KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, 16));
> + OPTIMIZER_HIDE_VAR(memset_size);
> + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, memset_size));
> kfree(ptr);
> }
>
> --
> 2.43.0
>

Reviewed-by: Andrey Konovalov <[email protected]>

Thanks!