On Wed, Jun 26, 2019 at 9:59 PM James Morris <jmorris@xxxxxxxxx> wrote: > This is not a criticism of the patch but a related issue which I haven't > seen discussed (apologies if it has). > > If signed code is loaded into ring 0, verified by the kernel, then > executed, you still lose your secure/trusted/verified boot state. If the > currently running kernel has been runtime-compromised, any signature > verification performed by the kernel cannot be trusted. > > This problem is out of scope for the lockdown threat model (which > naturally cannot include a compromised kernel), but folk should be aware > that signature-verified kexec does not provide equivalent assurance to a > full reboot on a secure-boot system. By that metric, on a secure boot system how do we determine that code running in the firmware environment wasn't compromised before it launched the initial signed kernel?
