Messages in this thread | | | Date | Fri, 29 Jul 2022 20:22:36 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/bugs: Do not enable IBPB at firmware entry when IBPB is not available |
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On Thu, Jul 28, 2022 at 02:01:57PM -0300, Thadeu Lima de Souza Cascardo wrote: > I may be completely wrong here, so excuse me throwing out this idea. > > But isn't it also possible that userspace attacks the kernel by leveraging > speculative execution when in firmware? So even when firmware is trusted, it > might not have mitigations like retpoline and rethunks. So userspace will train > the BTB in order to make a RET in the firmware speculate to a firmware gadget > that may spill out kernel bits to the cache. > > Even though there is some limited mapping when doing the firmware calls, there > are still some kernel pages mapped.
Yah, I dunno. That's why I raised this and added Andy. I certainly see your point tho.
And what I know is, I don't want to be dealing with imaginary virt guest configurations just because some cloud providers wanna do whatever they like.
I've put this mitigation selection spaghetti on my to-give-a-stern-look list. Because it is looking insane already and it'll get even worse with time.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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