CVE-2024-35996

In the Linux kernel, the following vulnerability has been resolved: cpu:
Re-enable CPU mitigations by default for !X86 architectures Rename x86’s to
CPU_MITIGATIONS, define it in generic code, and force it on for all
architectures exception x86. A recent commit to turn mitigations off by
default if SPECULATION_MITIGATIONS=n kinda sorta missed that
“cpu_mitigations” is completely generic, whereas SPECULATION_MITIGATIONS is
x86-specific. Rename x86’s SPECULATIVE_MITIGATIONS instead of keeping both
and have it select CPU_MITIGATIONS, as having two configs for the same
thing is unnecessary and confusing. This will also allow x86 to use the
knob to manage mitigations that aren’t strictly related to speculative
execution. Use another Kconfig to communicate to common code that
CPU_MITIGATIONS is already defined instead of having x86’s menu depend on
the common CPU_MITIGATIONS. This allows keeping a single point of contact
for all of x86’s mitigations, and it’s not clear that other architectures
want to allow disabling mitigations at compile-time.