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

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Message-ID: <ZuAa9DxCNwvFsZ50@pollux>
Date: Tue, 10 Sep 2024 12:09:56 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Feng Tang <feng.tang@...el.com>
Cc: 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>, linux-mm@...ck.org,
	kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] mm/slub, kunit: Add testcase for krealloc redzone
 and zeroing

On Mon, Sep 09, 2024 at 09:29:58AM +0800, Feng Tang wrote:
> 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.
> 
> User can add "slub_debug" kernel cmdline parameter to test it.
> 
> [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>

> ---
>  lib/slub_kunit.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 46 insertions(+)
> 
> diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
> index 6e3a1e5a7142..03e0089149ad 100644
> --- a/lib/slub_kunit.c
> +++ b/lib/slub_kunit.c
> @@ -186,6 +186,51 @@ static void test_leak_destroy(struct kunit *test)
>  	KUNIT_EXPECT_EQ(test, 1, slab_errors);
>  }
>  
> +static void test_krealloc_redzone_zeroing(struct kunit *test)
> +{
> +	char *p;
> +	int i;
> +
> +	KUNIT_TEST_REQUIRES(test, __slub_debug_enabled());
> +
> +	/* Allocate a 64B kmalloc object */
> +	p = kzalloc(48, GFP_KERNEL);
> +	if (unlikely(is_kfence_address(p))) {
> +		kfree(p);
> +		return;
> +	}
> +	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);
> +
> +	/* Test grow with allocating a bigger 128B object */
> +	p = krealloc(p, 112, GFP_KERNEL | __GFP_ZERO);
> +	if (unlikely(is_kfence_address(p)))
> +		goto exit;
> +
> +	for (i = 56; i < 112; i++)
> +		KUNIT_EXPECT_EQ(test, p[i], 0);
> +	for (i = 112; i < 128; i++)
> +		KUNIT_EXPECT_EQ(test, p[i], SLUB_RED_ACTIVE);
> +
> +exit:
> +	kfree(p);
> +	kasan_enable_current();
> +}
> +
>  static int test_init(struct kunit *test)
>  {
>  	slab_errors = 0;
> @@ -196,6 +241,7 @@ static int test_init(struct kunit *test)
>  }
>  
>  static struct kunit_case test_cases[] = {
> +	KUNIT_CASE(test_krealloc_redzone_zeroing),
>  	KUNIT_CASE(test_clobber_zone),
>  
>  #ifndef CONFIG_KASAN
> -- 
> 2.34.1
>