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

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Date:   Mon, 3 Apr 2017 07:53:20 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Christoph Lameter <cl@...ux.com>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        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 Mon, Apr 03, 2017 at 09:03:50AM -0500, Christoph Lameter wrote:
> On Mon, 3 Apr 2017, Michael Ellerman wrote:
> 
> > At least in slab.c it seems that would allow you to "free" an object
> > from one kmem_cache onto the array_cache of another kmem_cache, which
> > seems fishy. But maybe there's a check somewhere I'm missing?
> 
> kfree can be used to free any object from any slab cache.

Is that a guarantee?  There's some wording in the RCU free code that
seems to indicate we can't rely on that being true.