[GIT PULL] Kernel lockdown for secure boot

Mike Galbraith efault at gmx.de
Wed Apr 4 13:29:03 UTC 2018

On Wed, 2018-04-04 at 08:57 -0400, Theodore Y. Ts'o wrote:
> On Wed, Apr 04, 2018 at 04:30:18AM +0000, Matthew Garrett wrote:
> > What I'm afraid of is this turning into a "security" feature that ends up
> > being circumvented in most scenarios where it's currently deployed - eg,
> > module signatures are mostly worthless in the non-lockdown case because you
> > can just grab the sig_enforce symbol address and then kexec a preamble that
> > flips it back to N regardless of the kernel config.
> Whoa.  Why doesn't lockdown prevent kexec?  Put another away, why
> isn't this a problem for people who are fearful that Linux could be
> used as part of a Windows boot virus in a Secure UEFI context?
> If lockdown simply included a requirement for a signed kernel for
> kexec --- and if kernel signing aren't available, to simply not alow
> kexec, wouldn't that take care of this case?
> This wouldn't even be all that much of a burden for non-distro users
> with lockdown enabled, since in my experience outside of enterprise
> and data center use cases, kexec isn't used...

Lots of folks use kdump, ergo kexec.

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