linux-kernel - [PATCH v2 5/5] mm/slub, kunit: Add testcase for krealloc redzone and zeroing

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Message-Id: <20240911064535.557650-6-feng.tang@intel.com>
Date: Wed, 11 Sep 2024 14:45:35 +0800
From: Feng Tang <feng.tang@...el.com>
To: Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Hyeonggon Yoo <42.hyeyoo@...il.com>,
	Andrey Konovalov <andreyknvl@...il.com>,
	Marco Elver <elver@...gle.com>,
	Shuah Khan <skhan@...uxfoundation.org>,
	David Gow <davidgow@...gle.com>,
	Danilo Krummrich <dakr@...nel.org>,
	Alexander Potapenko <glider@...gle.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Dmitry Vyukov <dvyukov@...gle.com>,
	Vincenzo Frascino <vincenzo.frascino@....com>
Cc: linux-mm@...ck.org,
	kasan-dev@...glegroups.com,
	linux-kernel@...r.kernel.org,
	Feng Tang <feng.tang@...el.com>
Subject: [PATCH v2 5/5] mm/slub, kunit: Add testcase for krealloc redzone and zeroing

Danilo Krummrich raised issue about krealloc+GFP_ZERO [1], and Vlastimil
suggested to add some test case which can sanity test the kmalloc-redzone
and zeroing by utilizing the kmalloc's 'orig_size' debug feature.

It covers the grow and shrink case of krealloc() re-using current kmalloc
object, and the case of re-allocating a new bigger object.

[1]. https://lore.kernel.org/lkml/20240812223707.32049-1-dakr@kernel.org/

Suggested-by: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Feng Tang <feng.tang@...el.com>
Reviewed-by: Danilo Krummrich <dakr@...nel.org>
---
Hi Danilo,

I keep your Reviewed-By tag, as I think this v2 mostly changes what kmalloc
slab to be used. Let me know if you want it dropped, thanks.

 lib/slub_kunit.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
index 6e3a1e5a7142..b3d158f38b98 100644
--- a/lib/slub_kunit.c
+++ b/lib/slub_kunit.c
@@ -186,6 +186,47 @@ static void test_leak_destroy(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, 1, slab_errors);
 }
 
+static void test_krealloc_redzone_zeroing(struct kunit *test)
+{
+	u8 *p;
+	int i;
+	struct kmem_cache *s = test_kmem_cache_create("TestSlub_krealloc", 64,
+				SLAB_KMALLOC|SLAB_STORE_USER|SLAB_RED_ZONE);
+
+	p = __kmalloc_cache_noprof(s, GFP_KERNEL, 48);
+	memset(p, 0xff, 48);
+
+	kasan_disable_current();
+	OPTIMIZER_HIDE_VAR(p);
+
+	/* Test shrink */
+	p = krealloc(p, 40, GFP_KERNEL | __GFP_ZERO);
+	for (i = 40; i < 64; i++)
+		KUNIT_EXPECT_EQ(test, p[i], SLUB_RED_ACTIVE);
+
+	/* Test grow within the same 64B kmalloc object */
+	p = krealloc(p, 56, GFP_KERNEL | __GFP_ZERO);
+	for (i = 40; i < 56; i++)
+		KUNIT_EXPECT_EQ(test, p[i], 0);
+	for (i = 56; i < 64; i++)
+		KUNIT_EXPECT_EQ(test, p[i], SLUB_RED_ACTIVE);
+
+	validate_slab_cache(s);
+	KUNIT_EXPECT_EQ(test, 0, slab_errors);
+
+	memset(p, 0xff, 56);
+	/* Test grow with allocating a bigger 128B object */
+	p = krealloc(p, 112, GFP_KERNEL | __GFP_ZERO);
+	for (i = 0; i < 56; i++)
+		KUNIT_EXPECT_EQ(test, p[i], 0xff);
+	for (i = 56; i < 112; i++)
+		KUNIT_EXPECT_EQ(test, p[i], 0);
+
+	kfree(p);
+	kasan_enable_current();
+	kmem_cache_destroy(s);
+}
+
 static int test_init(struct kunit *test)
 {
 	slab_errors = 0;
@@ -208,6 +249,7 @@ static struct kunit_case test_cases[] = {
 	KUNIT_CASE(test_kmalloc_redzone_access),
 	KUNIT_CASE(test_kfree_rcu),
 	KUNIT_CASE(test_leak_destroy),
+	KUNIT_CASE(test_krealloc_redzone_zeroing),
 	{}
 };
 
-- 
2.34.1