On Wed, Apr 4, 2018 at 5:57 AM Theodore Y. Ts'o [off-list ref] wrote:

On Wed, Apr 04, 2018 at 04:30:18AM +0000, Matthew Garrett wrote:

quoted

What I'm afraid of is this turning into a "security" feature that ends

up

quoted

being circumvented in most scenarios where it's currently deployed - eg,
module signatures are mostly worthless in the non-lockdown case because

you

quoted

can just grab the sig_enforce symbol address and then kexec a preamble

that

quoted

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.