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Subject: Re: [PATCH] slub: fix unreclaimable slab stat for bulk free
To:     Vlastimil Babka <vbabka@suse.cz>,
        Shakeel Butt <shakeelb@google.com>
CC:     Christoph Lameter <cl@linux.com>,
        Pekka Enberg <penberg@kernel.org>,
        "David Rientjes" <rientjes@google.com>,
        Michal Hocko <mhocko@suse.com>, "Roman Gushchin" <guro@fb.com>,
        Wang Hai <wanghai38@huawei.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Linux MM" <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <20210728155354.3440560-1-shakeelb@google.com>
 <8c14efe2-69dc-6eab-3cd5-c042576770e7@huawei.com>
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 <35a0b75a-f348-d21c-4ff4-fadba0c4db02@huawei.com>
 <43cf4e71-4dd4-dc37-a70f-553fe5cba126@suse.cz>
From:   Kefeng Wang <wangkefeng.wang@huawei.com>
Message-ID: <c5d57083-3666-ef75-4269-fbeb5809ddfd@huawei.com>
Date:   Tue, 3 Aug 2021 22:44:56 +0800
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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@huawei.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.

>
>>> .
>>>
> .
>