linux-kernel - Re: [STABLE PATCH] slub: make ->cpu

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Date:   Thu, 27 Sep 2018 15:26:38 +0000
From:   Christopher Lameter <cl@...ux.com>
To:     zhong jiang <zhongjiang@...wei.com>
cc:     gregkh@...ux-foundation.org, iamjoonsoo.kim@....com,
        rientjes@...gle.com, penberg@...nel.org, akpm@...ux-foundation.org,
        mhocko@...e.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [STABLE PATCH] slub: make ->cpu_partial unsigned int

On Thu, 27 Sep 2018, zhong jiang wrote:

> From: Alexey Dobriyan <adobriyan@...il.com>
>
>         /*
>          * cpu_partial determined the maximum number of objects
>          * kept in the per cpu partial lists of a processor.
>          */
>
> Can't be negative.

True.

> I hit a real issue that it will result in a large number of memory leak.
> Because Freeing slabs are in interrupt context. So it can trigger this issue.
> put_cpu_partial can be interrupted more than once.
> due to a union struct of lru and pobjects in struct page, when other core handles
> page->lru list, for eaxmple, remove_partial in freeing slab code flow, It will
> result in pobjects being a negative value(0xdead0000). Therefore, a large number
> of slabs will be added to per_cpu partial list.

That sounds like it needs more investigation. Concurrent use of page
fields for other purposes can cause serious bugs.

>
> I had posted the issue to community before. The detailed issue description is as follows.

I did not see it. Please make sure to CC the maintainers.