CVE Request - Linux kernel - securelevel/secureboot bypass.

[Wade Mealing <wmealing () redhat com>]

Gday,

I'm like to request a CVE for the following issue (paraphrasing Linn Crosetto):

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When the kernel was booted with UEFI Secure Boot enabled, securelevel is set. If kexec (either through crash or admin 
action) is then used to load the same kernel, after reboot securelevel is disabled. In this state, the system is 
missing the protections provided by securelevel, for example kexec may be used to load an unsigned kernel via the 
legacy system call kexec_load.

In the securelevel patchset, the state of UEFI Secure Boot is queried in the EFI stub, and sets a boot_params flag to 
indicate the state of UEFI Secure Boot. This flag is then used in setup_arch() to determine the correct state of 
securelevel. If the kernel is not booted via the EFI stub, securelevel is not set even if UEFI Secure Boot is enabled.

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TLDR: this allows a bypass the security mechanism of securelevel/secureboot combination.

This patchset affects Red Hat specific kernels as secureboot is not fully fully implemented upstream yet.

Thanks,

Wade Mealing
Red Hat Product Security team


References:
Patch: https://bugzilla.redhat.com/show_bug.cgi?id=1243998#c3
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1243998