2023-12-12 23:27:22

by Nico Pache

Subject: [PATCH] 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 size2 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..5aeba810ba70 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 size2 = 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(size2);
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, size2));
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 size2 = 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(size2);
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, size2));
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 size2 = 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(size2);
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, size2));
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 size2 = 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(size2);
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, size2));
kfree(ptr);
}

--
2.43.0

2023-12-13 14:34:40

by Andrey Konovalov

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

On Wed, Dec 13, 2023 at 12:27 AM 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 size2 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..5aeba810ba70 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 size2 = 2;

Let's name this variable access_size or memset_size. Here and in the
other changed tests.

> 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(size2);
> + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, size2));
> 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 size2 = 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(size2);
> + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, size2));
> 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 size2 = 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(size2);
> + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, size2));
> 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 size2 = 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(size2);
> + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, size2));
> kfree(ptr);
> }
>
> --
> 2.43.0
>

With the fix mentioned above addressed:

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

2023-12-13 21:42:58

by Nico Pache

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

On Wed, Dec 13, 2023 at 7:34 AM Andrey Konovalov <[email protected]> wrote:
>
> On Wed, Dec 13, 2023 at 12:27 AM 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 size2 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..5aeba810ba70 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 size2 = 2;
>
> Let's name this variable access_size or memset_size. Here and in the
> other changed tests.

Hi Andrey,

I agree that is a better variable name, but I chose size2 because
other kasan tests follow the same pattern.

Please let me know if you still want me to update it given that info
and I'll send a V2.

Cheers,
-- Nico

>
> > 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(size2);
> > + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, size2));
> > 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 size2 = 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(size2);
> > + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, size2));
> > 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 size2 = 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(size2);
> > + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, size2));
> > 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 size2 = 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(size2);
> > + KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, size2));
> > kfree(ptr);
> > }
> >
> > --
> > 2.43.0
> >
>
> With the fix mentioned above addressed:
>
> Reviewed-by: Andrey Konovalov <[email protected]>
>

2023-12-13 23:43:32

by Andrey Konovalov

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

On Wed, Dec 13, 2023 at 10:42 PM Nico Pache <[email protected]> wrote:
>
> > > diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
> > > index 8281eb42464b..5aeba810ba70 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 size2 = 2;
> >
> > Let's name this variable access_size or memset_size. Here and in the
> > other changed tests.
>
> Hi Andrey,
>
> I agree that is a better variable name, but I chose size2 because
> other kasan tests follow the same pattern.

These other tests use size1 and size2 to refer to different sizes of
krealloc allocations, which seems reasonable.

> Please let me know if you still want me to update it given that info
> and I'll send a V2.

Yes, please update the name.

Thank you!