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Date: Fri, 7 Jul 2017 12:06:57 -0500 (CDT)
From: Christoph Lameter <cl@...ux.com>
To: Kees Cook <keescook@...omium.org>
cc: Rik van Riel <riel@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, 
    Pekka Enberg <penberg@...nel.org>, David Rientjes <rientjes@...gle.com>, 
    Joonsoo Kim <iamjoonsoo.kim@....com>, 
    "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, 
    Ingo Molnar <mingo@...nel.org>, Josh Triplett <josh@...htriplett.org>, 
    Andy Lutomirski <luto@...nel.org>, 
    Nicolas Pitre <nicolas.pitre@...aro.org>, Tejun Heo <tj@...nel.org>, 
    Daniel Mack <daniel@...que.org>, 
    Sebastian Andrzej Siewior <bigeasy@...utronix.de>, 
    Sergey Senozhatsky <sergey.senozhatsky@...il.com>, 
    Helge Deller <deller@....de>, Linux-MM <linux-mm@...ck.org>, 
    Tycho Andersen <tycho@...ker.com>, LKML <linux-kernel@...r.kernel.org>, 
    "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v3] mm: Add SLUB free list pointer obfuscation

On Fri, 7 Jul 2017, Kees Cook wrote:

> If we also added a >0 offset, that would make things even less
> deterministic. Though I wonder if it would make the performance impact
> higher. The XOR patch right now is very light.

There would be barely any performance impact if you keep the offset within
a cacheline since most objects start on a cacheline boundary. The
processor has to fetch the cacheline anyways.

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