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

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Date:   Thu, 27 Sep 2018 17:46:47 +0200
From:   Greg KH <gregkh@...ux-foundation.org>
To:     zhong jiang <zhongjiang@...wei.com>
Cc:     iamjoonsoo.kim@....com, rientjes@...gle.com, cl@...ux.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, Sep 27, 2018 at 10:43:40PM +0800, 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.
> 
> 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.
> 
> I had posted the issue to community before. The detailed issue description is as follows.
> 
> Link: https://www.spinics.net/lists/kernel/msg2870979.html
> 
> After applying the patch, The issue is fixed. So the patch is a effective bugfix.
> It should go into stable.

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>