Intel Alder Lake, ARM CPUs Affected by New Spectre Vulnerability

silversurfer

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VUSec security research group and Intel on Tuesday disclosed a yet another Spectre-class speculative execution vulnerability called branch history injection (BHI). The new exploit affects all of Intel processors released in the recent years, including the latest Alder Lake CPUs, and select Arm cores. By contrast, AMD's chips are believed to be unaffected.

BHI is a proof-of-concept attack that affects CPUs already vulnerable to Spectre V2 exploits, but with all kinds of mitigations already in place. The new exploit bypasses Intel's eIBRS and Arm's CSV2 mitigations, reports Phoronix. BHI re-enables cross-privilege Spectre-v2 exploits, allows kernel-to-kernel (so-called intra-mode BTI) exploits, and allows perpetrators to inject predictor entries into the global branch prediction history to make kernel leak data, reports VUSec. As a result, arbitrary kernel memory on select CPUs can be leaked and potentially reveal confidential information, including passwords. An example of how such a leak can happen was published here.
All of Intel's processors beginning with Haswell (launched in 2013) and extending to the latest Ice Lake-SP and Alder Lake are affected by the vulnerability, but Intel is about to release a software patch that will mitigate the issue.

Numerous cores from Arm, including Cortex A15, A57, A72 as well as Neoverse V1, N1, and N2 are also affected. Arm is expected to release software mitigations for its cores. What is unclear is whether custom versions of these cores (e.g., select cores from Qualcomm) are also affected and when the potential security holes will be covered.
 

The_King

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It was only a matter of time. Still early days for this ADL CPU, its less than 6 months old since release.

Now to see how much performance loss will come from the software patch. Hopefully its not much
or noticeable has these CPUs are really great value for money especially the cheaper non K versions.
 

plat1098

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Wow, looks like we can add AMD to the list now.


Now to see how much performance loss will come from the software patch. Hopefully its not much

I know, right? By the way, Is anyone else getting a little perturbed by AMD and its expanding list of issues and problems in Windows? What is going on there? You wonder what goes on at these big tech firms when nobody's watching. 😒

giphy.gif
 

The_King

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What other recent issues are there? I must have missed some news.
Most likely the fTPM stutter bug issue.
 

The_King

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Intel CPUs Suffer Performance Hit From New Spectre-v2 Mitigations​

According to Phoronix's Core i9-12900K (Alder Lake) results, networking and storage performance went down the toilet after enabling Retpolines. The publication recorded a 26.7% performance loss on the former and 14.5% on the latter. That's the hallmark of these mitigations: Any external I/O from the chip takes a hard hit. Workloads like web browsing or image manipulation in GIMP didn't show a huge impact.

The Core i7-1185G7 (Tiger Lake) took an even more detrimental hit to storage performance. The results showed 35.6% and 34.1% lower performance in OSBench and Flexible IO Tester, respectively. But again, workloads that don't rely on I/O or networking didn't show significant performance loss. These include gaming, web browsing, and other daily tasks.

Phoronix noted that AMD processors aren't safe from BHI even though modern Zen chips already leverage Retpolines. The problem is that AMD's LFENCE/JMP-based implementation of Retpolines isn't good enough to fend off BHI, so the chipmaker is shifting to general Retpolines. The impact of the transition for AMD processors is unknown, but Phoronix is already conducting new tests to find out.

It's possible Intel and other software developers will be able to reduce the impact of the BHI mitigations with additional time and effort, but for the time being, enabling the patches could prove very painful on servers and other systems that do a lot of I/O intensive work.
 

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AMD CPUs See Less Than 10% Performance Drop From Revised Spectre-v2 Mitigations​

Spectre-v2 isn't going anywhere soon. VUSec, a group of researchers from Vrije Universiteit Amsterdam, recently discovered Branch History Injection (BHI), a byproduct of Spectre-v2 that affects Intel and Arm processors. While Intel has taken a performance hit up to 35%, AMD's processors got off easy, according to Phoronix's latest report.
The Ryzen 9 5950X (Vermeer) suffered a 54% performance reduction with the Stress-NG (Context Switching) benchmark. Stress-NG is similar to Prime95 for Windows users so it isn’t the best metric for measuring performance from a consumer workload standpoint. However, besides that specific benchmark, the Ryzen 9 5950X held up pretty well. There was only a 5.3% and 5% drop in networking and storage performance, respectively. In comparison, the Core i9-12900K (Alder Lake) experienced performance hits of 26.7% and 14.5% in the networking and storage department.

Compared to the Ryzen 9 5950X, the Ryzen 9 5900HX (Cezanne) wasn't affected as much with Stress-NG. The mobile Zen 3 chip only saw 22% lower performance. However, the results revealed a higher toll on networking and storage performance. With the generic Retpoline, the Ryzen 9 5900X took a 9.2% and 9.1% hit in the former and latter, respectively.

It indeed came as a surprise that generic Retpoline didn't significantly impact AMD's EPYC server processors that handle more intensive I/O workloads. For example, with the EPYC 72F3, Phoronix only logged 8.9% lower networking performance and 7.2% lower storage performance. In addition, some workloads even benefitted from enabling generic Retpoline, showing improvements ranging from 2.2% to 3.8%.

Phoronix conducted its tests in Linux 5.17 kernel, so it remains to be seen if Windows users will experience similar margins regarding performance penalties. As per the publication, Microsoft reportedly will or has patched Windows so it won’t take long for us to find out.