Date: Mon, 3 Apr 2017 07:53:20 -0700
From: Matthew Wilcox <willy@infradead.org>
To: Christoph Lameter <cl@linux.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
        Kees Cook <keescook@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>, Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: Add additional consistency check
Message-ID: <20170403145320.GD30811@bombadil.infradead.org>
References: <20170331164028.GA118828@beast>
 <20170331143317.3865149a6b6112f0d1a63499@linux-foundation.org>
 <CAGXu5jK8RrHwa1Uv464=5+T5iBnhhx796CdLcJMAA88wi8bzaA@mail.gmail.com>
 <874ly6gnuo.fsf@concordia.ellerman.id.au>
 <alpine.DEB.2.20.1704030903010.4100@east.gentwo.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.20.1704030903010.4100@east.gentwo.org>
User-Agent: Mutt/1.7.1 (2016-10-04)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 514
Lines: 11

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.