linux-kernel - Re: [PATCH] mm: Add additional consistency check

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Message-ID: <alpine.DEB.2.20.1704180834570.13829@east.gentwo.org>
Date:   Tue, 18 Apr 2017 08:37:13 -0500 (CDT)
From:   Christoph Lameter <cl@...ux.com>
To:     Michal Hocko <mhocko@...nel.org>
cc:     Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: Add additional consistency check

On Tue, 18 Apr 2017, Michal Hocko wrote:

> Are you even reading those emails? First of all we are talking about
> slab here. Secondly I've already pointed out that the BUG_ON(!PageSlab)
> in kmem_freepages is already too late because we do operate on a
> potential garbage from invalid page...

Before I forget:

1. The patch affects both slab and slub since it patches mm/slab.h and is
called by both allocators.

2. The check in the patch we are discussing here when calling
kmem_cache_free() will be executing before kmem_freepages() is called
in slab.