Re: [PATCH] kasan: add atomic tests

[Andrey Konovalov <andreyknvl@gmail.com>]

On Fri, Feb 2, 2024 at 12:33 PM Paul Heidekrüger
<paul.heidekrueger@tum.de> wrote:
>
> Test that KASan can detect some unsafe atomic accesses.
>
> As discussed in the linked thread below, these tests attempt to cover
> the most common uses of atomics and, therefore, aren't exhaustive.
>
> CC: Marco Elver <elver@google.com>
> CC: Andrey Konovalov <andreyknvl@gmail.com>
> Link: https://lore.kernel.org/all/20240131210041.686657-1-paul.heidekrueger@tum.de/T/#u
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=214055
> Signed-off-by: Paul Heidekrüger <paul.heidekrueger@tum.de>
> ---
> Changes PATCH RFC v2 -> PATCH v1:
> * Remove casts to void*
> * Remove i_safe variable
> * Add atomic_long_* test cases
> * Carry over comment from kasan_bitops_tags()
>
> Changes PATCH RFC v1 -> PATCH RFC v2:
> * Adjust size of allocations to make kasan_atomics() work with all KASan modes
> * Remove comments and move tests closer to the bitops tests
> * For functions taking two addresses as an input, test each address in a separate function call.
> * Rename variables for clarity
> * Add tests for READ_ONCE(), WRITE_ONCE(), smp_load_acquire() and smp_store_release()
>
>  mm/kasan/kasan_test.c | 79 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 79 insertions(+)
>
> diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
> index 8281eb42464b..4ef2280c322c 100644
> --- a/mm/kasan/kasan_test.c
> +++ b/mm/kasan/kasan_test.c
> @@ -1150,6 +1150,84 @@ static void kasan_bitops_tags(struct kunit *test)
>         kfree(bits);
>  }
>
> +static void kasan_atomics_helper(struct kunit *test, void *unsafe, void *safe)
> +{
> +       int *i_unsafe = (int *)unsafe;
> +
> +       KUNIT_EXPECT_KASAN_FAIL(test, READ_ONCE(*i_unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, WRITE_ONCE(*i_unsafe, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, smp_load_acquire(i_unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, smp_store_release(i_unsafe, 42));
> +
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_read(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_set(unsafe, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_add(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_sub(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_inc(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_dec(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_and(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_andnot(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_or(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_xor(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_xchg(unsafe, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_cmpxchg(unsafe, 21, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_try_cmpxchg(unsafe, safe, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_try_cmpxchg(safe, unsafe, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_sub_and_test(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_dec_and_test(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_inc_and_test(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_add_negative(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_add_unless(unsafe, 21, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_inc_not_zero(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_inc_unless_negative(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_dec_unless_positive(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_dec_if_positive(unsafe));
> +
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_read(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_set(unsafe, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_add(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_sub(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_inc(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_dec(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_and(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_andnot(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_or(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_xor(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_xchg(unsafe, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_cmpxchg(unsafe, 21, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_try_cmpxchg(unsafe, safe, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_try_cmpxchg(safe, unsafe, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_sub_and_test(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_dec_and_test(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_inc_and_test(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_add_negative(42, unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_add_unless(unsafe, 21, 42));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_inc_not_zero(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_inc_unless_negative(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_dec_unless_positive(unsafe));
> +       KUNIT_EXPECT_KASAN_FAIL(test, atomic_long_dec_if_positive(unsafe));
> +}
> +
> +static void kasan_atomics(struct kunit *test)
> +{
> +       void *a1, *a2;
> +
> +       /*
> +        * Just as with kasan_bitops_tags(), we allocate 48 bytes of memory such
> +        * that the following 16 bytes will make up the redzone.
> +        */
> +       a1 = kzalloc(48, GFP_KERNEL);
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, a1);
> +       a2 = kzalloc(sizeof(int), GFP_KERNEL);

I think this should be sizeof(atomic_long_t) or sizeof(long),
otherwise a2 will not work as the safe argument for
atomic_long_try_cmpxchg on 64-bit architectures.

> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, a1);
> +
> +       /* Use atomics to access the redzone. */
> +       kasan_atomics_helper(test, a1 + 48, a2);
> +
> +       kfree(a1);
> +       kfree(a2);
> +}
> +
>  static void kmalloc_double_kzfree(struct kunit *test)
>  {
>         char *ptr;
> @@ -1553,6 +1631,7 @@ static struct kunit_case kasan_kunit_test_cases[] = {
>         KUNIT_CASE(kasan_strings),
>         KUNIT_CASE(kasan_bitops_generic),
>         KUNIT_CASE(kasan_bitops_tags),
> +       KUNIT_CASE(kasan_atomics),
>         KUNIT_CASE(kmalloc_double_kzfree),
>         KUNIT_CASE(rcu_uaf),
>         KUNIT_CASE(workqueue_uaf),
> --
> 2.40.1
>