Spectre-like bug could mean big performance drop for AMD and Intel CPUs

Posted on Monday, May 03 2021 @ 11:48 CEST by Thomas De Maesschalck
Researchers from the University of Virginia and the University of California San Diego have unearthed a new Spectre-like security vulnerability that is capable of beating all previous mitigations. This time, it's a vulnerability that affects both AMD and Intel processors. A vulnerability in the way x86 processors break down complex instructions into micro-ops, which are stored in micro-ops cache, allows attackers to cause a data leak.

How the vulnerability works

TechPowerUp offers a brief summary of how the exploit works:
Modern x86 processors break down complex instructions into smaller RISC-like units called micro-ops, in the frontend, where it makes the design of the backend part much simples. The micro-ops are stored in the micro-ops cache. The paper is describing micro-op cache-based timing channel exploits in three primary settings: "a) across code regions within the same thread, but operating at different privilege levels, (b) across different co-located threads running simultaneously on different SMT contexts (logical cores) within the same physical core, and (c) two transient execution attack variants that leverage the micro-op cache to leak transiently accessed secrets, bypassing several existing hardware and software-based mitigations, including Intel's recommended LFENCE."

Patches could result in big performance drops

A fix for this new Spectre-like bug is expected to result in a performance drop. The exploit deals with low-level caching structure so a potential fix could result in quite severe performance degradation.

About the Author

Thomas De Maesschalck

Thomas has been messing with computer since early childhood and firmly believes the Internet is the best thing since sliced bread. Enjoys playing with new tech, is fascinated by science, and passionate about financial markets. When not behind a computer, he can be found with running shoes on or lifting heavy weights in the weight room.

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