Messages in this thread | | | Subject | Re: [PATCH v18 05/25] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states | From | Dave Hansen <> | Date | Fri, 29 Jan 2021 14:53:12 -0800 |
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On 1/29/21 2:35 PM, Yu, Yu-cheng wrote: >> Andy Cooper just mentioned on IRC about this nugget in the spec: >> >> XRSTORS on CET state will do reserved bit and canonicality >> checks on the state in similar manner as done by the WRMSR to >> these state elements. >> >> We're using copy_kernel_to_xregs_err(), so the #GP *should* be OK. >> Could we prove this out in practice, please? >>> > Do we want to verify that setting reserved bits in CET XSAVES states > triggers GP? Then, yes, I just verified it again. Thanks for > reminding. Do we have any particular case relating to this?
I want to confirm that it triggers #GP and kills userspace without the kernel WARN'ing or otherwise being visibly unhappy.
What about the return-to-userspace path after a ptracer writes content to the CET fields? I don't see the same tolerance for errors in __fpregs_load_activate(), for instance.
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