Tuesday, January 12, 2016

Intel CPU Bugs of 2015

Dan Luu (via Hacker News and Peter Steinberger):

We’ve seen at least two serious bugs in Intel CPUs in the last quarter, and it’s almost certain there are more bugs lurking. Back when I worked at a company that produced Intel compatible CPUs, we did a fair amount of testing and characterization of Intel CPUs; as someone fresh out of school who’d previously assumed that CPUs basically worked, I was surprised by how many bugs we were able to find. Even though I never worked on the characterization and competitive analysis side of things, I still personally found multiple Intel CPU bugs just in the normal course of doing my job, poking around to verify things that seemed non-obvious to me. Turns out things that seem non-obvious to me are sometimes also non-obvious to Intel engineers. As more services move to the cloud and the impact of system hang and reset vulnerabilities increases, we’ll see more black hats investing time in finding CPU bugs. We should expect to see a lot more of these when people realize that it’s much easier than it seems to find these bugs. There was a time when a CPU family might only have one bug per year, with serious bugs happening once every few years, or even once a decade, but we seem to have moved past that. In part, that’s because “unpredictable system behavior” have moved from being an annoying class of bugs that forces you to restart your computation to an attack vector that lets anyone with an AWS account attack your cloud-hosted services, but it’s mostly because CPUs are now complex enough that they’ve become too complicated to test effectively. Ironically, we have hardware virtualization is supposed to help us with security, but the virtualization is so complicated4 that the hardware virtualization implementation is likely to expose “unpredictable system behavior” bugs that wouldn’t otherwise have existed.

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