Re: Hyper-Threading Vulnerability

[Dave Jones]

On Fri, May 13, 2005 at 07:00:12PM -0400, Lee Revell wrote:
 > On Fri, 2005-05-13 at 23:47 +0100, Alan Cox wrote:
 > > On Gwe, 2005-05-13 at 22:59, Matt Mackall wrote:
 > > > It might not be much of a problem though. If he's a bit off per guess
 > > > (really impressive), he'll still be many bits off by the time there's
 > > > enough entropy in the primary pool to reseed the secondary pool so he
 > > > can check his guesswork.
 > > 
 > > You can also disable the tsc to user space in the intel processors.
 > > Thats something they anticipated as being neccessary in secure
 > > environments long ago. This makes the attack much harder.
 > 
 > And break the hundreds of apps that depend on rdtsc?  Am I missing
 > something?

If those apps depend on rdtsc being a) present, and b) working
without providing fallbacks, they're already broken.

There's a reason its displayed in /proc/cpuinfo's flags field,
and visible through cpuid. Apps should be testing for presence
before assuming features are present.

		Dave

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