Spectre Kernel will not boot (4.13.0-29-generic)

[cement_head]

Updated to 4.13.0-29-generic FROM 4.13.0-26-generic and machine refuses to boot. Hangs at early stage of Plymouth splash screen, hard reset required.

This bug report list 4.13.0-26-generic as cause, not so, but I didn't know how to report for 4.13.0-29-generic, given that it hangs.

$ lsb_release -a
LSB Version: core-9.20160110ubuntu0.2-amd64:core-9.20160110ubuntu0.2-noarch:printing-9.20160110ubuntu0.2-amd64:printing-9.20160110ubuntu0.2-noarch:security-9.20160110ubuntu0.2-amd64:security-9.20160110ubuntu0.2-noarch
Distributor ID: Ubuntu
Description: Ubuntu 16.04.3 LTS
Release: 16.04
Codename: xenial

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: linux-image-4.13.0-26-generic 4.13.0-26.29~16.04.2
ProcVersionSignature: Ubuntu 4.13.0-26.29~16.04.2-generic 4.13.13
Uname: Linux 4.13.0-26-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.15
Architecture: amd64
CurrentDesktop: Unity
Date: Sat Jan 13 08:09:37 2018
InstallationDate: Installed on 2017-09-29 (105 days ago)
InstallationMedia: Ubuntu 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
ProcEnviron:
 LANGUAGE=en_US
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: linux-hwe
UpgradeStatus: No upgrade log present (probably fresh install)

[cement_head (andorjkiss)]

The 4.13.0-30-generic kernel will also NOT boot.

[Jakob Guldberg Aaes (jakob1379)]

I have problems with 4.13.0-31 as well :/

[cement_head (andorjkiss)]

4.13.0-31-generic boots for me and behaves as expected (no issues) However, variant one is still active:

Spectre and Meltdown mitigation detection tool v0.31

Checking for vulnerabilities against running kernel Linux 4.13.0-31-generic #34~16.04.1-Ubuntu SMP Fri Jan 19 17:11:01 UTC 2018 x86_64
CPU is Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz

CVE-2017-5753 [bounds check bypass] aka 'Spectre Variant 1'
* Checking count of LFENCE opcodes in kernel: YES
> STATUS: NOT VULNERABLE (114 opcodes found, which is >= 70, heuristic to be improved when official patches become available)

CVE-2017-5715 [branch target injection] aka 'Spectre Variant 2'
* Mitigation 1
* Hardware (CPU microcode) support for mitigation
* The SPEC_CTRL MSR is available: NO
* The SPEC_CTRL CPUID feature bit is set: NO
* Kernel support for IBRS: YES
* IBRS enabled for Kernel space: NO
* IBRS enabled for User space: NO
* Mitigation 2
* Kernel compiled with retpoline option: NO
* Kernel compiled with a retpoline-aware compiler: NO
> STATUS: VULNERABLE (IBRS hardware + kernel support OR kernel with retpoline are needed to mitigate the vulnerability)

CVE-2017-5754 [rogue data cache load] aka 'Meltdown' aka 'Variant 3'
* Kernel supports Page Table Isolation (PTI): YES
* PTI enabled and active: YES
* Checking if we're running under Xen PV (64 bits): NO
> STATUS: NOT VULNERABLE (PTI mitigates the vulnerability)

A false sense of security is worse than no security at all, see --disclaimer

[Po-Hsu Lin (cypressyew)]

Closing this bug with Won't fix as this kernel / release is no longer supported.
Please feel free to open a new bug report if you're still experiencing this on a newer release (Bionic 18.04.3 / Disco 19.04)
Thanks!