linux-kernel - Re: [PATCH] slub: Relocate freelist pointer to middle of object

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Message-ID: <alpine.DEB.2.21.2003151410220.14449@www.lameter.com>
Date:   Sun, 15 Mar 2020 14:11:38 +0000 (UTC)
From:   Christopher Lameter <cl@...ux.com>
To:     Kees Cook <keescook@...omium.org>
cc:     David Laight <David.Laight@...LAB.COM>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Daniel Micay <danielmicay@...il.com>,
        Vitaly Nikolenko <vnik@...synt.com>,
        Silvio Cesare <silvio.cesare@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] slub: Relocate freelist pointer to middle of object

On Wed, 11 Mar 2020, Kees Cook wrote:

> > Sounds good. You could even randomize the position to avoid attacks on via
> > the freelist pointer.
>
> That's a good point. "offset" is just calculated once, and for many
> slabs, the available space is quite large. I wonder what the best

Correct.

> practice might be for how far from the edge to stay. Hmmm. Maybe simply
> carve it into thirds, and randomize the offset within the middle third?

Take off the first and last word and randomize within the space that is
left?