linux-kernel - Re: [PATCH] slub: kunit catch kmem_cache

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Message-ID: <Ynj5GZuXG6CgCUJp@hyeyoo>
Date:   Mon, 9 May 2022 20:20:57 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Paran Lee <p4ranlee@...il.com>
Cc:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        linux-kernel@...r.kernel.org, linux-mm@...r.kernel.org,
        Oliver Glitta <glittao@...il.com>,
        Austin Kim <austindh.kim@...il.com>
Subject: Re: [PATCH] slub: kunit catch kmem_cache_alloc failed

On Fri, May 06, 2022 at 01:53:19PM +0900, Paran Lee wrote:
> Catch kmem_cache_alloc failed on slub kunit test.
> 
> Signed-off-by: Paran Lee <p4ranlee@...il.com>
> ---
>  lib/slub_kunit.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
> index 8662dc6cb509..7b80241dd498 100644
> --- a/lib/slub_kunit.c
> +++ b/lib/slub_kunit.c
> @@ -32,6 +32,11 @@ static void test_next_pointer(struct kunit *test)
>  	struct kmem_cache *s = kmem_cache_create("TestSlub_next_ptr_free", 64, 0,
>  				SLAB_POISON, NULL);
>  	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +	if (!p) {
> +		kunit_err(test, "Allocation failed: %s\n", __func__);
> +		kmem_cache_destroy(s);
> +		return;
> +	}
>  	unsigned long tmp;
>  	unsigned long *ptr_addr;
>  
> @@ -77,6 +82,11 @@ static void test_first_word(struct kunit *test)
>  	struct kmem_cache *s = kmem_cache_create("TestSlub_1th_word_free", 64, 0,
>  				SLAB_POISON, NULL);

Recently SLAB_NO_USER_FLAGS is added for test caches.
Looks like it's not based on Vlastimil's slab tree:
https://git.kernel.org/pub/scm/linux/kernel/git/vbabka/slab.git

>  	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +	if (!p) {
> +		kunit_err(test, "Allocation failed: %s\n", __func__);
> +		kmem_cache_destroy(s);
> +		return;
> +	}
>  
>  	kmem_cache_free(s, p);
>  	*p = 0x78;
> @@ -92,6 +102,11 @@ static void test_clobber_50th_byte(struct kunit *test)
>  	struct kmem_cache *s = kmem_cache_create("TestSlub_50th_word_free", 64, 0,
>  				SLAB_POISON, NULL);
>  	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +	if (!p) {
> +		kunit_err(test, "Allocation failed: %s\n", __func__);
> +		kmem_cache_destroy(s);
> +		return;
> +	}
>  
>  	kmem_cache_free(s, p);
>  	p[50] = 0x9a;
> @@ -108,6 +123,11 @@ static void test_clobber_redzone_free(struct kunit *test)
>  	struct kmem_cache *s = kmem_cache_create("TestSlub_RZ_free", 64, 0,
>  				SLAB_RED_ZONE, NULL);
>  	u8 *p = kmem_cache_alloc(s, GFP_KERNEL);
> +	if (!p) {
> +		kunit_err(test, "Allocation failed: %s\n", __func__);
> +		kmem_cache_destroy(s);
> +		return;
> +	}
>  
>  	kasan_disable_current();
>  	kmem_cache_free(s, p);
> -- 
> 2.25.1
> 

To be more paranoid kmem_cache_create() can also fail - but I'm not sure
these checks are useful for tests.

-- 
Thanks,
Hyeonggon