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

[Vlastimil Babka]

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@xxxxxxxxxx> 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.

> Any suggestion will be appreciated, thanks.

debug_pagealloc could help to catch a use-after-free earlier

> 
>> .
>>