However, the North American manufacturer has now admitted that its Zen 3 CPUs are vulnerable to a type of attack similar to Specter.
For most of our readers, AMD is currently the best processor manufacturer. However, this does not mean that, like any other, it does not present problems and flaws in some of its products. Of course you have them too. However, the difference between a good and bad company is that the first one assumes its mistakes in an attempt to offer the best experience to its customer. And that's what AMD has done now.
AMD Zen 3 CPUs are vulnerable to Specter-like attacks
According to an article recently published by AMD entitled "Security Analysis of AMD Predictive Store Forwarding", the manufacturer confirms that an optimization within the microarchitecture of its Zen 3 CPUs can be exploited in a similar way to the Specter vulnerabilities. This was a vulnerability that haunted some rival Intel's processors a few years ago.
In short, the implementation of Predictive Store Forwarding (PSF) reopens attack opportunities similar to Specter v1, v2 and v3, due to its speculative nature. According to AMD, PSF is a hardware optimization "designed to improve the performance of code execution by predicting dependencies between loads and stores". Thus, the PSF makes predictions to allow the processor to execute subsequent instructions more quickly. However, it does create a vulnerability when its prediction is incorrect.
AMD says that incorrect predictions can arise from two situations. One is when the storage / loading set had a dependency for a while, but then it stopped having a dependency. Another is if there is a alias in the structure of the PSF predictor and the alias be used when it shouldn't.
Since PSF speculation is limited to the context of the current program, the impact of poor PSF speculation is similar to that of speculative storage diversion (Specter v4).
The Ryzen 5000 and Epyc 7003 processors use the Zen 3 architecture and, as such, are affected by this vulnerability.
AMD also states that it is possible to disable this optimization, however this will result in a performance penalty. Thus, the manufacturer does not consider it worthwhile, except for more critical evolutions of processors.
You can read the report in full here.
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