Hello,
I have these messages on boot with Fedora 26 and kernel 4.12 and up.
sept. 12 00:56:17 hp kernel: Couldn't get size: 0x800000000000000e
sept. 12 00:56:17 hp kernel: MODSIGN: Couldn't get UEFI db list
sept. 12 00:56:17 hp kernel: Couldn't get size: 0x800000000000000e
Chromebook HP 14 (Falco) with MattDevo firmware
https://bugzilla.redhat.com/show_bug.cgi?id=1470995
Thanks !