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

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Message-Id: <20250728-kasan-tsbrcu-noquarantine-test-v1-1-fa24d9ab7f41@google.com>
Date: Mon, 28 Jul 2025 17:25:07 +0200
From: Jann Horn <jannh@...gle.com>
To: 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: Vlastimil Babka <vbabka@...e.cz>, kasan-dev@...glegroups.com, 
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, 
 Jann Horn <jannh@...gle.com>
Subject: [PATCH] kasan: add test for SLAB_TYPESAFE_BY_RCU quarantine
 skipping

Verify that KASAN does not quarantine objects in SLAB_TYPESAFE_BY_RCU slabs
if CONFIG_SLUB_RCU_DEBUG is off.

Suggested-by: Andrey Konovalov <andreyknvl@...il.com>
Signed-off-by: Jann Horn <jannh@...gle.com>
---
Feel free to either take this as a separate commit or squash it into the
preceding "[PATCH] kasan: skip quarantine if object is still accessible
under RCU".

I tested this by running KASAN kunit tests for x86-64 with KASAN
and tracing manually enabled; there are two failing tests but those
seem unrelated (kasan_memchr is unexpectedly not detecting some
accesses, and kasan_strings is also failing).
---
 mm/kasan/kasan_test_c.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/mm/kasan/kasan_test_c.c b/mm/kasan/kasan_test_c.c
index 5f922dd38ffa..15d3d82041bf 100644
--- a/mm/kasan/kasan_test_c.c
+++ b/mm/kasan/kasan_test_c.c
@@ -1073,6 +1073,41 @@ 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);
+
+	p = kmem_cache_alloc(cache, GFP_KERNEL);
+	if (!p) {
+		kunit_err(test, "Allocation failed: %s\n", __func__);
+		kmem_cache_destroy(cache);
+		return;
+	}
+
+	kmem_cache_free(cache, p);
+	p2 = kmem_cache_alloc(cache, GFP_KERNEL);
+	if (!p2) {
+		kunit_err(test, "Allocation failed: %s\n", __func__);
+		kmem_cache_destroy(cache);
+		return;
+	}
+	KUNIT_ASSERT_PTR_EQ(test, p, p2);
+
+	kmem_cache_free(cache, p2);
+	kmem_cache_destroy(cache);
+}
+
 static void kmem_cache_double_destroy(struct kunit *test)
 {
 	struct kmem_cache *cache;
@@ -2098,6 +2133,7 @@ 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

-- 
Jann Horn <jannh@...gle.com>