20 Feb
2023
20 Feb
'23
6:56 p.m.
On Mon, Feb 20, 2023 at 10:52 AM Borislav Petkov bp@alien8.de wrote:
On Mon, Feb 20, 2023 at 10:44:21AM -0800, KP Singh wrote:
No it cannot with IBRS which is really just KERNEL_IBRS enabled, we
See my other reply. The intent is there to be able to do it. What needs to be figured out now is *why* we said no STIBP with IBRS? Was it an omission or was there some intent behind it.
Sure, it looks like an omission to me, we wrote a POC on Skylake that was able to do cross-thread training with the current set of mitigations.
STIBP with IBRS is still correct if spectre_v2=ibrs had really meant IBRS everywhere, but just means KERNEL_IBRS, which means only kernel is protected, userspace is still unprotected.
-- Regards/Gruss, Boris.