Re: [Cerowrt-devel] KASLR: Do we have to worry about other arches than x86?

[Jonathan Morton <chromatix99@gmail.com>]

As I thought:

	https://lkml.org/lkml/2017/12/27/2

"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."

So it only affects *Intel* CPUs, though it's not yet clear to me how widespread the bug is in Intel-land.  Therefore ARM, PPC, etc are unaffected, and AMD might just get even more of a leg up in the server biz than previously anticipated.

Reading between the lines, I get the definite impression that this is a hardware exploit which uses *speculative* memory accesses to perform Rowhammer attacks in privileged memory areas.  So we probably shouldn't worry about it too much on consumer PCs or routers, even if they do use Intel x86 CPUs, except for the performance impact we might see where the mitigation is in place.  The performance impact would primarily affect system calls and context switches, I think, with much less impact on general computation.

 - Jonathan Morton