Re: [PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down

[David Howells]

David Howells <dhowells@xxxxxxxxxx> wrote:

> > I don't like the idea that the lockdown (which is a runtime
> > thing) requires a compile time option (KEXEC_VERIFY_SIG) that
> > forces the verification even when the kernel is then not locked
> > down at runtime.
> 
> It doesn't.  The EPERM only triggers if:
> 
>  (1) File signatures aren't mandatory (ie. CONFIG_KEXEC_VERIFY_SIG) is not
>      set, and
> 
>  (2) you're not using IMA appraisal to validate the file contents, and
> 
>  (3) lockdown mode is enabled.
> 
> If file signatures are mandatory or IMA appraisal is in use, then the lockdown
> state doesn't need to be checked.

Having said that, I do see your point, I think.  We should still let through
validly signed images, even if signatures aren't mandatory in lockdown mode.

David