Linux 6.5-rc4 Brings Change For Enabling STIBP On AMD Zen 4 Auto IBRS Systems

[phoronix]

Phoronix: Linux 6.5-rc4 Brings Change For Enabling STIBP On AMD Zen 4 Auto IBRS Systems

Last weekend I wrote about Zen 4's Automatic IBRS security feature needing STIBP enabled for protecting user-space processes. Single-Threaded Indirect Branch Predictors though haven't been enabled up to now with the Auto IBRS functionality on Linux. But the x86/urgent pull request sent out today ahead of the Linux 6.5-rc4 tagging makes that change...

https://www.phoronix.com/news/Linux-6.5-rc4-x86-urgent

[stormcrow]

Anyone know if this was marked "urgent" because of Zenbleed, or did someone come up with a separate exploit targeting Zen 4 processors running Linux that didn't have STIBP (so previous Spectre vulns weren't properly mitigated).

[Michael]

Anyone know if this was marked "urgent" because of Zenbleed, or did someone come up with a separate exploit targeting Zen 4 processors running Linux that didn't have STIBP (so previous Spectre vulns weren't properly mitigated).

The x86 fixes via tip/tip.git are always marked via the branch "x86/urgent"