Re: [RFC] perf: mmap2 not covering VM_CLONE regions

[Peter Zijlstra]

On Wed, Oct 02, 2013 at 02:59:32PM +0200, Stephane Eranian wrote:
> On Wed, Oct 2, 2013 at 2:46 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > On Wed, Oct 02, 2013 at 02:39:53PM +0200, Ingo Molnar wrote:
> >>  - then there are timing attacks, and someone having access to a PMU
> >>    context and who can trigger this SHA1 computation arbitrarily in task
> >>    local context can run very accurate and low noise timing attacks...
> >>
> >>    I don't think the kernel's sha_transform() is hardened against timing
> >>    attacks, it's performance optimized so it has variable execution time
> >>    highly dependent on plaintext input - which leaks information about the
> >>    plaintext.
> >
> > Typical user doesn't have enough priv to profile kernel space; once you
> > do you also have enough priv to see kernel addresses outright (ie.
> > kallsyms etc..).
> >
> I was going to say just that. But that's not the default, paranoid level
> is at 1 by default and not 2. So I supposedly can still do:

Oh right you are.. so yes that's a very viable avenue.
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