Spectre & Meltdown Defined January 2018

[phoronix]

Phoronix: Spectre & Meltdown Defined January 2018

A majority of last month was spent looking at and testing/benchmarking the Linux code to mitigate the much talked about Spectre and Meltdown CPU vulnerabilities...

http://www.phoronix.com/scan.php?page=news_item&px=January-2018-Spectre-Meltdown

[dungeon]

February was defined as shortest month, could we patch that somehow

[raom]

Anyone here knows if there is a way to disable the meltdown and spectre patches on Windows for AMD processors?

[DanL]

Anyone here knows if there is a way to disable the meltdown and spectre patches on Windows for AMD processors?

https://techreport.com/news/33172/optional-windows-update-disables-crash-causing-spectre-mitigations

I can't even even get my Llano laptop and Brisbane desktop to apply the mitigation patch successfully, even though MS supposedly fixed it.

[raom]

https://techreport.com/news/33172/optional-windows-update-disables-crash-causing-spectre-mitigations

I can't even even get my Llano laptop and Brisbane desktop to apply the mitigation patch successfully, even though MS supposedly fixed it.

That's only for spectre variant 2. Is the meltdown fix enabled for AMD processors at all?

[numacross]

That's only for spectre variant 2. Is the meltdown fix enabled for AMD processors at all?

I don't have any AMD hardware on hand to test, but you can use a PowerShell module to check if your hardware requires that fix: https://gallery.technet.microsoft.co...ntrol-e36f0050 or follow the direct PowerShell on-line installation as specified here https://support.microsoft.com/en-us/...erabilities-in

You're interested in:

Hardware requires kernel VA shadowing: True
Windows OS support for kernel VA shadow is enabled: True

[dungeon]

Is the meltdown fix enabled for AMD processors at all?

It isn't , but even if somehow it is - it shouldn't be:

A third technique is based on a software performance optimization. Software running in a lesser privilege mode
typically has page table mappings for more privileged code present in the page table context that is running. This
allows for high performance switching between the two modes and the software uses extra page table attributes
enforced by the hardware to restrict access to the privileged data when in lesser privileged modes. However, on
some processors it has been observed that if software accesses the more privileged data when the processor
is in a lesser privileged mode, the architectural fault may be delayed. This opens up a window for a speculative
execution attack where privileged data is then forwarded to subsequent instructions for speculative execution.
This is referred to as a variant 3 (Google Project Zero and Meltdown). No AMD processor has been designed with
this behavior and so we are not discussing mitigation steps in the rest of the document for this variant but we
are including it here for completeness. Software developers should use CPUID vendor ID checks to identify AMD
processors to avoid implementing variant 3 mitigations.

https://developer.amd.com/wp-content...Processors.pdf

Early on, during Linux kernel development that was enabled by mistake for AMD too, but now it isn't:

meltdown    spectre_v1  spectre_v2  
> cat /sys/devices/system/cpu/vulnerabilities/*
Not affected
Vulnerable
Mitigation: Full AMD retpoline

[dungeon]

Anyone here knows if there is a way to disable the meltdown and spectre patches on Windows for AMD processors?

BTW, why you wanna disable these? It is not recommended to disable it particulary now that everybody knows much about these and attack samples identified by antivirus companies are on raise by every day...



Maybe if you like pictures

http://www.zdnet.com/article/meltdown-spectre-malware-is-already-being-tested-by-attackers/

[numacross]

BTW, why you wanna disable these? It is not recommended to disable it particulary now that everybody knows much about these and attack samples identified by antivirus companies are on raise by every day...

For some the performance implications might be a good reason. Even Microsoft doesn't enable those mitigations on their Server versions by default but only on consumer ones.

[raom]

I don't have any AMD hardware on hand to test, but you can use a PowerShell module to check if your hardware requires that fix: https://gallery.technet.microsoft.co...ntrol-e36f0050 or follow the direct PowerShell on-line installation as specified here https://support.microsoft.com/en-us/...erabilities-in

You're interested in:

Hardware requires kernel VA shadowing: True
Windows OS support for kernel VA shadow is enabled: True

Thank you. It is false on both counts for my Phenom II machine.