Re: [PATCH V31 07/25] kexec_file: Restrict at runtime if the kernel is locked down

From: Matthew Garrett
Date: Mon Jun 24 2019 - 17:06:14 EST

On Sun, Jun 23, 2019 at 6:52 PM Dave Young <dyoung@xxxxxxxxxx> wrote:
> On 06/21/19 at 01:18pm, Matthew Garrett wrote:
> > I don't think so - we want it to be possible to load images if they
> > have a valid signature.
> I know it works like this way because of the previous patch. But from
> the patch log "When KEXEC_SIG is not enabled, kernel should not load
> images", it is simple to check it early for !IS_ENABLED(CONFIG_KEXEC_SIG) &&
> kernel_is_locked_down(reason, LOCKDOWN_INTEGRITY) instead of depending
> on the late code to verify signature. In that way, easier to
> understand the logic, no?

But that combination doesn't enforce signature validation? We can't
depend on !IS_ENABLED(CONFIG_KEXEC_SIG_FORCE) because then it'll
enforce signature validation even if lockdown is disabled.