Messages in this thread | | | From | Andrew Cooper <> | Subject | Re: Wake-up from suspend to RAM broken under `retbleed=stuff` | Date | Wed, 11 Jan 2023 22:06:56 +0000 |
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On 11/01/2023 11:45 am, Jan Beulich wrote: > On 11.01.2023 12:39, Andrew Cooper wrote: >> The bigger issue with stuff accounting is that nothing AFAICT accounts >> for the fact that any hypercall potentially empties the RSB in otherwise >> synchronous program flow. > But that's not just at hypercall boundaries, but effectively anywhere > (i.e. whenever the hypervisor decides to de-schedule the vCPU)?
Correct, but it's only the RET instructions that reliably underflow the RSB which can be usefully attacked.
The %rip at which Xen decides to de-schedule a vCPU are random from the point of view of an attacker.
~Andrew
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