linux-kernel - Re: [PATCH] slub: fix unreclaimable slab stat for bulk free

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Date:   Tue, 3 Aug 2021 22:44:56 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Vlastimil Babka <vbabka@...e.cz>,
        Shakeel Butt <shakeelb@...gle.com>
CC:     Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        "David Rientjes" <rientjes@...gle.com>,
        Michal Hocko <mhocko@...e.com>, "Roman Gushchin" <guro@...com>,
        Wang Hai <wanghai38@...wei.com>,
        Muchun Song <songmuchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Linux MM" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] slub: fix unreclaimable slab stat for bulk free


On 2021/8/3 22:29, Vlastimil Babka wrote:
> On 8/3/21 4:24 PM, Kefeng Wang wrote:
>> On 2021/7/29 22:03, Shakeel Butt wrote:
>>> On Wed, Jul 28, 2021 at 11:52 PM Kefeng Wang <wangkefeng.wang@...wei.com> wrote:
>>>> On 2021/7/28 23:53, Shakeel Butt wrote:
>>> I don't have a strong opinion on this. Please send a patch with
>>> reasoning if you want WARN_ON_ONCE here.
>> Ok, we met a BUG_ON(!PageCompound(page)) in kfree() twice in lts4.4, we are
>> still debugging it.
>>
>> It's different to analyses due to no vmcore, and can't be reproduced.
>>
>> WARN_ON() here could help us to notice the issue.
>>
>> Also is there any experience or known fix/way to debug this kinds of issue?
>> memory corruption?
> This would typically be a use-after-free/double-free - a problem of the slab
> user, not slab itself.

We enable KASAN to find whether or not there are some UAF/double free, 
no related

log for now.

>
>> Any suggestion will be appreciated, thanks.
> debug_pagealloc could help to catch a use-after-free earlier

OK, will try this, thanks.

>
>>> .
>>>
> .
>