[kernel-hardening] Re: [PATCH v2] mm: Add SLUB free list pointer obfuscation

[Rik van Riel <riel@redhat.com>]

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.