linux-kernel - Re: [PATCH v2] kasan: add test for SLAB_TYPESAFE_BY

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Message-ID: <5109febc-21b4-43fb-98a2-14c552c27bfe@suse.cz>
Date: Tue, 29 Jul 2025 18:51:32 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Jann Horn <jannh@...gle.com>, Andrey Ryabinin <ryabinin.a.a@...il.com>,
 Alexander Potapenko <glider@...gle.com>,
 Andrey Konovalov <andreyknvl@...il.com>, Dmitry Vyukov <dvyukov@...gle.com>,
 Vincenzo Frascino <vincenzo.frascino@....com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: kasan-dev@...glegroups.com, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] kasan: add test for SLAB_TYPESAFE_BY_RCU quarantine
 skipping

On 7/29/25 18:49, Jann Horn wrote:
> Verify that KASAN does not quarantine objects in SLAB_TYPESAFE_BY_RCU slabs
> if CONFIG_SLUB_RCU_DEBUG is off.
> 
> Signed-off-by: Jann Horn <jannh@...gle.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
> changes in v2:
>  - disable migration to ensure that all SLUB operations use the same
>    percpu state (vbabka)
>  - use EXPECT instead of ASSERT for pointer equality check so that
>    expectation failure doesn't terminate the test with migration still
>    disabled
> ---
>  mm/kasan/kasan_test_c.c | 38 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/mm/kasan/kasan_test_c.c b/mm/kasan/kasan_test_c.c
> index 5f922dd38ffa..0d50402d492c 100644
> --- a/mm/kasan/kasan_test_c.c
> +++ b/mm/kasan/kasan_test_c.c
> @@ -1073,6 +1073,43 @@ static void kmem_cache_rcu_uaf(struct kunit *test)
>  	kmem_cache_destroy(cache);
>  }
>  
> +/*
> + * Check that SLAB_TYPESAFE_BY_RCU objects are immediately reused when
> + * CONFIG_SLUB_RCU_DEBUG is off, and stay at the same address.
> + */
> +static void kmem_cache_rcu_reuse(struct kunit *test)
> +{
> +	char *p, *p2;
> +	struct kmem_cache *cache;
> +
> +	KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_SLUB_RCU_DEBUG);
> +
> +	cache = kmem_cache_create("test_cache", 16, 0, SLAB_TYPESAFE_BY_RCU,
> +				  NULL);
> +	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, cache);
> +
> +	migrate_disable();
> +	p = kmem_cache_alloc(cache, GFP_KERNEL);
> +	if (!p) {
> +		kunit_err(test, "Allocation failed: %s\n", __func__);
> +		goto out;
> +	}
> +
> +	kmem_cache_free(cache, p);
> +	p2 = kmem_cache_alloc(cache, GFP_KERNEL);
> +	if (!p2) {
> +		kunit_err(test, "Allocation failed: %s\n", __func__);
> +		goto out;
> +	}
> +	KUNIT_EXPECT_PTR_EQ(test, p, p2);
> +
> +	kmem_cache_free(cache, p2);
> +
> +out:
> +	migrate_enable();
> +	kmem_cache_destroy(cache);
> +}
> +
>  static void kmem_cache_double_destroy(struct kunit *test)
>  {
>  	struct kmem_cache *cache;
> @@ -2098,6 +2135,7 @@ static struct kunit_case kasan_kunit_test_cases[] = {
>  	KUNIT_CASE(kmem_cache_double_free),
>  	KUNIT_CASE(kmem_cache_invalid_free),
>  	KUNIT_CASE(kmem_cache_rcu_uaf),
> +	KUNIT_CASE(kmem_cache_rcu_reuse),
>  	KUNIT_CASE(kmem_cache_double_destroy),
>  	KUNIT_CASE(kmem_cache_accounted),
>  	KUNIT_CASE(kmem_cache_bulk),
> 
> ---
> base-commit: 0df7d6c9705b283d5b71ee0ae86ead05bd3a55a9
> change-id: 20250728-kasan-tsbrcu-noquarantine-test-5c723367e056
> prerequisite-change-id: 20250723-kasan-tsbrcu-noquarantine-e207bb990e24:v1
> prerequisite-patch-id: 4fab9d3a121bfcaacc32a40f606b7c04e0c6fdd0
>