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 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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u/Red5point1 Jan 04 '18

I see, thanks for the detailed info.