Date: Thu, 29 Jun 2017 13:54:13 -0400 From: Rik van Riel <riel@...hat.com> To: Kees Cook <keescook@...omium.org>, Christoph Lameter <cl@...ux.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, Laura Abbott <labbott@...hat.com>, Daniel Micay <danielmicay@...il.com>, 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>, LKML <linux-kernel@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: Re: [PATCH v2] mm: Add SLUB free list pointer obfuscation On Thu, 2017-06-29 at 10:47 -0700, Kees Cook wrote: > On Thu, Jun 29, 2017 at 10:05 AM, Christoph Lameter <cl@...ux.com> > wrote: > > On Sun, 25 Jun 2017, Kees Cook wrote: > > > > > The difference gets lost in the noise, but if the above is > > > sensible, > > > it's 0.07% slower. ;) > > > > Hmmm... These differences add up. Also in a repetative benchmark > > like that > > you do not see the impact that the additional cacheline use in the > > cpu > > cache has on larger workloads. Those may be pushed over the edge of > > l1 or > > l2 capacity at some point which then causes drastic regressions. > > Even if that is true, it may be worth it to some people to have the > protection. Given that is significantly hampers a large class of heap > overflow attacks, I think it's an important change to have. I'm > not > suggesting this be on by default, it's cleanly behind > CONFIG-controlled macros, and is very limited in scope. If you can > Ack > it we can let system builders decide if they want to risk a possible > performance hit. I'm pretty sure most distros would like to have this > protection. I could certainly see it being useful for all kinds of portable and network-connected systems where security is simply much more important than performance.
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