Re: [GIT PULL] Kernel lockdown for secure boot

[Matthew Garrett]

On Wed, Apr 4, 2018 at 5:57 AM Theodore Y. Ts'o <tytso@xxxxxxx> 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?

It does - I was talking about the non-lockdown case. In the lockdown case
you can only kexec images you trust, so there's no problem. Red Hat have
been shipping a signed kdump image for years.