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Message-ID: <0df9277d-6f10-4af6-abd7-50a275489a72@linux.dev>
Date: Mon, 3 Jun 2024 16:05:41 +0800
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Subject: Re: [PATCH 1/3] slab: check the return value of
 check_bytes_and_report()
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To: Vlastimil Babka <vbabka@suse.cz>,
 "Christoph Lameter (Ampere)" <cl@gentwo.org>
Cc: Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>,
 Joonsoo Kim <iamjoonsoo.kim@lge.com>,
 Andrew Morton <akpm@linux-foundation.org>,
 Roman Gushchin <roman.gushchin@linux.dev>,
 Hyeonggon Yoo <42.hyeyoo@gmail.com>, Feng Tang <feng.tang@intel.com>,
 linux-mm@kvack.org, linux-kernel@vger.kernel.org, zhouchengming@bytedance.com
References: <20240528-b4-slab-debug-v1-0-8694ef4802df@linux.dev>
 <20240528-b4-slab-debug-v1-1-8694ef4802df@linux.dev>
 <4e4d45b5-c684-2d93-49d2-b179a088c2d5@gentwo.org>
 <dc7181fc-5b16-46f1-a267-0eb5781f692a@linux.dev>
 <2ff52c5e-4b6b-4b3d-9047-f00967315d3e@suse.cz>
From: Chengming Zhou <chengming.zhou@linux.dev>
In-Reply-To: <2ff52c5e-4b6b-4b3d-9047-f00967315d3e@suse.cz>
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On 2024/6/3 15:46, Vlastimil Babka wrote:
> On 5/31/24 10:31 AM, Chengming Zhou wrote:
>> On 2024/5/30 23:20, Christoph Lameter (Ampere) wrote:
>>> On Tue, 28 May 2024, Chengming Zhou wrote:
>>>
>>>> diff --git a/mm/slub.c b/mm/slub.c
>>>> index 0809760cf789..de57512734ac 100644
>>>> --- a/mm/slub.c
>>>> +++ b/mm/slub.c
>>>> @@ -1324,9 +1324,10 @@ static int check_object(struct kmem_cache *s, struct slab *slab,
>>>>         }
>>>>     } else {
>>>>         if ((s->flags & SLAB_POISON) && s->object_size < s->inuse) {
>>>> -            check_bytes_and_report(s, slab, p, "Alignment padding",
>>>> +            if (!check_bytes_and_report(s, slab, p, "Alignment padding",
>>>>                 endobject, POISON_INUSE,
>>>> -                s->inuse - s->object_size);
>>>> +                s->inuse - s->object_size))
>>>> +                return 0;
>>>>         }
>>>>     }
>>>
>>> This change means we will then skip the rest of the checks in check_object() such as the poison check.
>>
>> Yeah, only when this padding checking failed.
>>
>> Now, we always abort checking and return 0 when the first checking error happens,
>> such as redzones checking above.
> 
> Yes your patch will make it consistent. But IMHO it would be better to do
> all the checks without skipping, report their specific error findings in
> check_bytes_and_report() but not print_trailer(). Once all checks were done,
> if any found an error, print the trailer once from check_object(). Thoughts?

Ok, it's feasible, will change to this.

> 
>> Thanks.
>