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.
