this post was submitted on 12 Aug 2023
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Steam Deck

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Linux Kernel Updated To Add Zenbleed Fix For Valve's Steam Deck (www.phoronix.com)
submitted 1 year ago by [email protected] to c/[email protected]
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[–] [email protected] 25 points 1 year ago

This is the best summary I could come up with:

Last month when the Linux kernel was mitigated for Zenbleed as a CPU vulnerability affecting AMD Zen 2 processors, it turns out the Steam Deck APU was accidentally left without coverage.

An x86/urgent pull request sent out today for the Linux 6.5 kernel and for back-porting to current stable Linux kernel releases will extend the Zenbleed mitigation to protect Steam Deck gamers.

Most notable with these fixes is adding models 0x90-0x91 to the range of AMD Zenbleed-affected Zen 2 processors.

It looks like the Steam Deck's custom APU was just accidentally left out in the original Zenbleed patch.

This patch enables the Zenbleed fallback fix until a proper CPU microcode update is available for the Steam Deck.

Zenbleed (CVE-2023-20593) was disclosed last month after this data leakage vulnerability was discovered by a Google researcher.

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[–] [email protected] 18 points 1 year ago (1 children)

If there is a performance cost for this, hopefully it isn't too high given the limited resources of the Deck.

[–] [email protected] 8 points 1 year ago* (last edited 1 year ago) (1 children)

The headroom required for the mitigation is statistically insignificant according to the details page on the cve.

see the comparison chart.

[–] [email protected] 0 points 1 year ago

Good to see. That seems to have been the case with most of the AMD vulnerabilities actually. Which stands in stark contrast to the "up to 50%" hit of Intel's Downfall, and some of the other Intel vulnerabilities.

[–] [email protected] 7 points 1 year ago (2 children)

What is Zenbleed?

[–] [email protected] 8 points 1 year ago

It's a vulnerability that affects AMD CPUs that can potentially lead to unintentional/malicious data leak.

https://security.googleblog.com/2023/08/downfall-and-zenbleed-googlers-helping.html?m=1