Messages in this thread | | | Date | Fri, 1 Mar 2019 17:15:17 +0000 | From | Catalin Marinas <> | Subject | Re: [PATCH v5 03/10] arm64: add sysfs vulnerability show for meltdown |
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On Fri, Mar 01, 2019 at 10:53:50AM -0600, Jeremy Linton wrote: > On 3/1/19 10:20 AM, Catalin Marinas wrote: > > On Fri, Mar 01, 2019 at 10:12:09AM -0600, Jeremy Linton wrote: > > > On 3/1/19 1:11 AM, Andre Przywara wrote: > > > > On 2/26/19 7:05 PM, Jeremy Linton wrote: > > > > > +ssize_t cpu_show_meltdown(struct device *dev, struct > > > > > device_attribute *attr, > > > > > + char *buf) > > > > > +{ > > > > > + if (arm64_kernel_unmapped_at_el0()) > > > > > + return sprintf(buf, "Mitigation: KPTI\n"); > > > > > + > > > > > + if (__meltdown_safe) > > > > > + return sprintf(buf, "Not affected\n"); > > > > > > > > Shall those two checks be swapped? So it doesn't report about a KPTI > > > > mitigation if the CPU is safe, but we enable KPTI because of KASLR > > > > having enabled it? Or is that a different knob? > > > > > > Hmmm, I think having it this way reflects the fact that the machine is > > > mitigated independent of whether it needed it. The force on case is similar. > > > The machine may not have needed the mitigation but it was forced on. > > > > So is this patchset about showing vulnerabilities _and_ mitigations or > > just one of them? > > Well, I don't think there is a way to express a mitigated but not vulnerable > state in the current ABI. This set is mostly just to bring us in line with > the current ABI expectations.
Looking at the ABI doc, it states:
"Not affected" CPU is not affected by the vulnerability "Vulnerable" CPU is affected and no mitigation in effect "Mitigation: $M" CPU is affected and mitigation $M is in effect
So, yes, we don't have mitigated but not vulnerable. Therefore I think we should stick to "not affected" and swap the lines above as per Andre's comment. This file is about Meltdown vulnerability and mitigation, not KASLR hardening.
-- Catalin
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