Re: [STABLE PATCH] slub: make ->cpu_partial unsigned int

[Greg KH]

On Sun, Sep 30, 2018 at 06:28:21PM +0800, zhong jiang wrote:
> From: Alexey Dobriyan <adobriyan@xxxxxxxxx>
> 
> [ Upstream commit e5d9998f3e09359b372a037a6ac55ba235d95d57 ]
> 
>         /*
>          * 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.
> Becuase 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.
> 
> 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.
> 
> Link: http://lkml.kernel.org/r/20180305200730.15812-15-adobriyan@xxxxxxxxx
> Signed-off-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
> Acked-by: Christoph Lameter <cl@xxxxxxxxx>
> Cc: Pekka Enberg <penberg@xxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx> # 4.4.x

This didn't apply to 4.14.y and any reason you didn't cc: the stable
mailing list for the other stable developers to see it?

I've fixed up the patch, but next time please always cc: the stable
list.

thanks,

greg k-h