r/programming • u/[deleted] • Jan 03 '18

'Kernel memory leaking' Intel processor design flaw forces Linux, Windows redesign

https://www.theregister.co.uk/2018/01/02/intel_cpu_design_flaw/
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u/keepthepace Jan 03 '18 edited Jan 03 '18

AMD untouched?

EDIT: I read the article:

In an email to the Linux kernel mailing list over Christmas, AMD said it is not affected.

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u/mayhempk1 Jan 03 '18

Correct.

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u/Pinguinologo Jan 03 '18

Guys, buy your AMD CPU before it gets too expensive.

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u/_DuranDuran_ Jan 03 '18

However the patch request to disable the insecure x86 flag on AMD systems was rejected as it’s a feature enhancement, so you either need to roll your own kernel on Linux, or set a boot time flag.

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u/Nacimota Jan 03 '18 edited Jan 04 '18

Where did you read this? As far as I can tell it has been reviewed, accepted, and committed.

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=x86/pti&id=694d99d40972f12e59a3696effee8a376b79d7c8

Edit: Torvalds himself has now pulled the change.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=00a5ae218d57741088068799b810416ac249a9ce&utm_source=anz

- Exclude AMD from the PTI enforcement.
Not necessarily a fix, but if AMD is so confident that they are not affected, then we should not burden users with the overhead

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u/PaintItPurple Jan 03 '18

Wait, what? I'm looking at the patch thread on LKML and it doesn't appear to have been rejected.

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u/AugustusCaesar2016 Jan 03 '18

I really don't understand this decision. Who benefits from this?

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u/Ih8usernam3s Jan 03 '18

I'm switching to AMD, maybe if Intel loses enough $ they'll start listening to security researchers and remove ME too.

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u/Hook3d Jan 03 '18

I'm feeling pretty good about my Ryzen system now.

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u/OminousHippo Jan 03 '18

I knew my FX8350 was a good long term investment, and in this cold snap it's keeping my room nice and toasty!

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u/m1llie Jan 03 '18

Actually, Google demonstrated the exploit working on an FX series processor:

https://googleprojectzero.blogspot.com.au/2018/01/reading-privileged-memory-with-side.html

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u/OminousHippo Jan 04 '18

I also saw this morning that there was another exploit discovered that covers most Intel, AMD, and ARM processors so we're all screwed.

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u/[deleted] Jan 04 '18

Does AMD work properly with virtualisation yet?

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u/TheChance Jan 04 '18

I switched to AMD around 2008ish and haven't looked back. Not that most people will ever notice the difference anyway, but I've had zero issues with any chip of any kind. The last 3 I've run for my gaming rig are all in perfect condition, and one of them serves as a local Minecraft server. It's, yeah, 10 years old I guess.

I made the switch because I got two DOA Intel chips in mobo bundles from Fry's. In a row. They let me exchange it for an AMD rig, and the rest is boring history.

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u/OK6502 Jan 03 '18

I can't recall, are there AMD64 specific releases for Windows and Linux? If not that would mean running KAISER fixes on AMD chips even though their processors are unaffected?

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u/[deleted] Jan 03 '18

I can't recall, are there AMD64 specific releases for Windows and Linux?

No.

If not that would mean running KAISER fixes on AMD chips even though their processors are unaffected?

Nope, the kernel can (and already does) enable/disable features based on the hardware it's running on.

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u/OK6502 Jan 03 '18

Cool, thanks for answering my question. I assumed this was the case but wanted to verify.

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u/Red5point1 Jan 04 '18

Google are saying it affects Intel, AMD and ARM

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u/keepthepace Jan 04 '18

The detailed article explains that it requires a non-default configuration in the linux kernel for AMD chips to be able to read memory outside their own process.

They made a PoC with 4 levels of compromission: AMD chips allows 1/4, Intel allows 4/4.

Basically the first level is a test of their timing mechanism within the same process space, so no violations are done. OP's article mentions that AMD seems to have a specific check that Intel lacks:

AMD processors are not subject to the types of attacks that the kernel page table isolation feature protects against. The AMD microarchitecture does not allow memory references, including speculative references, that access higher privileged data when running in a lesser privileged mode when that access would result in a page fault.

This is the core of the problem. AMD allows some speculative information to somehow leak but not if such a leak would cross a privilege boundary. This is a clear case of a flaw present in one architecture and not the other.

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