DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 6561FC0B2013
Message-ID: <1498758853.6130.2.camel@redhat.com>
Subject: Re: [PATCH v2] mm: Add SLUB free list pointer obfuscation
From: Rik van Riel <riel@redhat.com>
To: Kees Cook <keescook@chromium.org>, Christoph Lameter <cl@linux.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Laura Abbott <labbott@redhat.com>,
        Daniel Micay <danielmicay@gmail.com>,
        Pekka Enberg <penberg@kernel.org>,
        David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@kernel.org>, Josh Triplett <josh@joshtriplett.org>,
        Andy Lutomirski <luto@kernel.org>,
        Nicolas Pitre <nicolas.pitre@linaro.org>, Tejun Heo <tj@kernel.org>,
        Daniel Mack <daniel@zonque.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Helge Deller <deller@gmx.de>, LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>,
        "kernel-hardening@lists.openwall.com" 
        <kernel-hardening@lists.openwall.com>
Date: Thu, 29 Jun 2017 13:54:13 -0400
In-Reply-To: <CAGXu5jLLFKnboaLJKGcGT-Ra80ZzAf3jZ=zex6vd8uDQamBJxg@mail.gmail.com>
References: <20170623015010.GA137429@beast>
         <CAGXu5jJEi_CS-CB=-4369TFRyeN4oQdmGS+HV-zoi4rSPpq3Jw@mail.gmail.com>
         <alpine.DEB.2.20.1706291204460.17478@east.gentwo.org>
         <CAGXu5jLLFKnboaLJKGcGT-Ra80ZzAf3jZ=zex6vd8uDQamBJxg@mail.gmail.com>
Organization: Red Hat, Inc
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1271
Lines: 32

On Thu, 2017-06-29 at 10:47 -0700, Kees Cook wrote:
> On Thu, Jun 29, 2017 at 10:05 AM, Christoph Lameter <cl@linux.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[1], 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.