Date: Wed, 5 Jul 2017 16:30:56 -0700 From: Kees Cook <keescook@...omium.org> To: Andrew Morton <akpm@...ux-foundation.org>, Christoph Lameter <cl@...ux.com> Cc: Rik van Riel <riel@...hat.com>, Tycho Andersen <tycho@...ker.com>, 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: Re: [PATCH v2] mm: Add SLUB free list pointer obfuscation On Thu, Jun 29, 2017 at 10:56 AM, Tycho Andersen <tycho@...ker.com> wrote: > On Thu, Jun 29, 2017 at 01:54:13PM -0400, Rik van Riel wrote: >> 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. > > Indeed, I believe we would enable this in our kernels. Andrew and Christoph, What do you think about carrying this for -mm, since people are interested in it and it's a very narrow change behind a config (with a large impact on reducing the expoitability of freelist pointer overwrites)? -Kees -- Kees Cook Pixel Security
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