efi: runtime: avoid EFIv2 runtime services on Apple x86 machines

In the Linux kernel, the following vulnerability has been resolved:

efi: runtime: avoid EFIv2 runtime services on Apple x86 machines

Aditya reports [0] that his recent MacbookPro crashes in the firmware

when using the variable services at runtime. The culprit appears to be a

call to QueryVariableInfo(), which we did not use to call on Apple x86

machines in the past as they only upgraded from EFI v1.10 to EFI v2.40

firmware fairly recently, and QueryVariableInfo() (along with

UpdateCapsule() et al) was added in EFI v2.00.

The only runtime service introduced in EFI v2.00 that we actually use in

Linux is QueryVariableInfo(), as the capsule based ones are optional,

generally not used at runtime (all the LVFS/fwupd firmware update

infrastructure uses helper EFI programs that invoke capsule update at

boot time, not runtime), and not implemented by Apple machines in the

first place. QueryVariableInfo() is used to 'safely' set variables,

i.e., only when there is enough space. This prevents machines with buggy

firmwares from corrupting their NVRAMs when they run out of space.

Given that Apple machines have been using EFI v1.10 services only for

the longest time (the EFI v2.0 spec was released in 2006, and Linux

support for the newly introduced runtime services was added in 2011, but

the MacbookPro12,1 released in 2015 still claims to be EFI v1.10 only),

let's avoid the EFI v2.0 ones on all Apple x86 machines.

[0] https://lore.kernel.org/all/[email protected]/