Description: efi: Restrict efivar_ssdt_load when the kernel is locked down
References:
 https://git.zx2c4.com/american-unsigned-language/tree/american-unsigned-language.sh
 https://www.openwall.com/lists/oss-security/2020/06/14/1
 https://www.openwall.com/lists/oss-security/2020/07/30/2
Notes:
Bugs:
upstream: released (5.4-rc1) [1957a85b0032a81e6482ca4aab883643b8dae06e]
4.19-upstream-stable: N/A "lockdown not implemented"
4.9-upstream-stable: N/A "lockdown not implemented"
sid: released (5.2.6-1) [features/all/lockdown/0032-efi-Restrict-efivar_ssdt_load-when-the-kernel-is-loc.patch]
4.19-buster-security: released (4.19.132-1) [features/all/lockdown/0032-efi-Restrict-efivar_ssdt_load-when-the-kernel-is-loc.patch]
4.9-stretch-security: ignored "securelevel included but not supported"