Re: [PATCH V31 07/25] kexec_file: Restrict at runtime if the kernel is locked down
From: Mimi Zohar
Date: Mon Jun 24 2019 - 17:27:49 EST
On Mon, 2019-06-24 at 14:06 -0700, Matthew Garrett wrote:
> 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.
I agree with Dave. ÂThere should be a stub lockdown function to
prevent enforcing lockdown when it isn't enabled.