linux-kernel - Re: [PATCH] mm: check the function kmalloc

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Message-ID: <be9a1d54-0558-dbee-fcac-0f357ea32db9@nfschina.com>
Date:   Tue, 14 Jun 2022 17:26:40 +0800
From:   tury <renyu@...china.com>
To:     Vlastimil Babka <vbabka@...e.cz>, cl@...ux.com
Cc:     penberg@...nel.org, rientjes@...gle.com, iamjoonsoo.kim@....com,
        akpm@...ux-foundation.org, roman.gushchin@...ux.dev,
        42.hyeyoo@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, liqiong@...china.com,
        qixu@...china.com, hukun@...china.com, yuzhe@...china.com
Subject: Re: [PATCH] mm: check the function kmalloc_slab return value



在 2022年06月14日 16:48, Vlastimil Babka 写道:
> On 6/14/22 10:39, Ren Yu wrote:
>> As the possible failure of the kmalloc_slab,
>> it should be better to check it.
> AFAIK failure is not possible, kmalloc_slab() is not an allocation function,
> it just returns a member of kmalloc_caches array, which is initialized
> elsewhere and shouldn't contain NULLs. So the patch seems unnecessary to me.
>
>> Signed-off-by: Ren Yu <renyu@...china.com>
>> Reported-by: kernel test robot <lkp@...el.com>
>> ---
>> v2:
>> - fix build waring integer from pointer without a cast
>> ---
>> ---
>>   mm/slab.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/mm/slab.c b/mm/slab.c
>> index f8cd00f4ba13..72135e555827 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -2064,6 +2064,8 @@ int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
>>   	if (OFF_SLAB(cachep)) {
>>   		cachep->freelist_cache =
>>   			kmalloc_slab(cachep->freelist_size, 0u);
>> +		if (unlikely(ZERO_OR_NULL_PTR(cachep->freelist_cache)))
> The usual way is "if (!cachep->freelist_cache)". Not sure why check for ZERO.
>
>> +			return cachep->freelist_cache;
> So in case of NULL this would return NULL, thus 0, but __kmem_cache_create()
> return 0 on success, so it's wrong. You would have to return e.g. -ENOMEM.
Thanks for the advice ,I'll be re-patching
>
>>   	}
>>   
>>   	err = setup_cpu_cache(cachep, gfp);
>