[Beowulf] Intel CPU design bug & security flaw - kernel fix imposes performance penalty

John Hearns hearnsj at googlemail.com
Wed Jan 3 00:46:52 PST 2018

Thanks Chris.  In the past there have been Intel CPU 'bugs' trumpeted, but
generally these are fixed with a microcode update.
This looks different, as it is a fundamental part of the chips architecture.
However the Register article says: "It allows normal user programs – to
discern to some extent the layout or contents of protected kernel memory

I guess the phrase "to some extent" is the vital one here. Are there any
security exploits which use this information? I guess it is inevitable that
one will be engineered now that this is known about. The question I am
really asking is should we worry about this for real world systems. And I
guess tha answer is that if the kernel developers are worried enough then
yes we should be too. Comments please.

On 3 January 2018 at 06:56, Greg Lindahl <lindahl at pbm.com> wrote:

> On Wed, Jan 03, 2018 at 02:46:07PM +1100, Christopher Samuel wrote:
> > There appears to be no microcode fix possible and the kernel fix will
> > incur a significant performance penalty, people are talking about in the
> > range of 5%-30% depending on the generation of the CPU. :-(
> The performance hit (at least for the current patches) is related to
> system calls, which HPC programs using networking gear like OmniPath
> or Infiniband don't do much of.
> -- greg
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