linux-kernel - Re: [RFC][PATCH 0/3] Speed up SLUB poisoning + disable checks

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Date:	Wed, 27 Jan 2016 00:21:35 +0900
From:	Joonsoo Kim <js1304@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Laura Abbott <labbott@...oraproject.org>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	kernel-hardening@...ts.openwall.com,
	Kees Cook <keescook@...omium.org>
Subject: Re: [RFC][PATCH 0/3] Speed up SLUB poisoning + disable checks

2016-01-27 0:01 GMT+09:00 Christoph Lameter <cl@...ux.com>:
> On Tue, 26 Jan 2016, Joonsoo Kim wrote:
>
>> I doesn't follow up that discussion, but, I think that reusing
>> SLAB_POISON for slab sanitization needs more changes. I assume that
>> completeness and performance is matter for slab sanitization.
>>
>> 1) SLAB_POISON isn't applied to specific kmem_cache which has
>> constructor or SLAB_DESTROY_BY_RCU flag. For debug, it's not necessary
>> to be applied, but, for slab sanitization, it is better to apply it to
>> all caches.
>
> Those slabs can be legitimately accessed after the objects were freed. You
> cannot sanitize nor poison.

Oops... you are right. I misunderstand what SLAB_DESTROY_BY_RCU is.
Now, it's clear to me.

Thanks.