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

* Peter Zijlstra <peterz@infradead.org> 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 didn't mean profiling - that's not a 'timing attack'.

A simple RDTSC done around repeated calls to sha_transform() using kernel
functionality is.

Thanks,

Ingo


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