USN-3718-2: Linux kernel (HWE) regression

21 July 2018

A regression that caused boot failures was fixed in the Linux kernel.

Releases

Packages

  • linux-azure - Linux kernel for Microsoft Azure Cloud systems
  • linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems
  • linux-hwe - Linux hardware enablement (HWE) kernel

Details

USN-3695-2 fixed vulnerabilities in the Linux Hardware Enablement
Kernel (HWE) kernel for Ubuntu 16.04 LTS. Unfortunately, the fix
for CVE-2018-1108 introduced a regression where insufficient early
entropy prevented services from starting, leading in some situations
to a failure to boot, This update addresses the issue.

We apologize for the inconvenience.

Original advisory details:

Jann Horn discovered that the Linux kernel's implementation of random
seed data reported that it was in a ready state before it had gathered
sufficient entropy. An attacker could use this to expose sensitive
information. (CVE-2018-1108)

Wen Xu discovered that the ext4 file system implementation in the Linux
kernel did not properly initialize the crc32c checksum driver. A local
attacker could use this to cause a denial of service (system crash).
(CVE-2018-1094)

It was discovered that the cdrom driver in the Linux kernel contained an
incorrect bounds check. A local attacker could use this to expose sensitive
information (kernel memory). (CVE-2018-10940)

Wen Xu discovered that the ext4 file system implementation in the Linux
kernel did not properly validate xattr sizes. A local attacker could use
this to cause a denial of service (system crash). (CVE-2018-1095)

Jann Horn discovered that the 32 bit adjtimex() syscall implementation for
64 bit Linux kernels did not properly initialize memory returned to user
space in some situations. A local attacker could use this to expose
sensitive information (kernel memory). (CVE-2018-11508)

It was discovered that an information leak vulnerability existed in the
floppy driver in the Linux kernel. A local attacker could use this to
expose sensitive information (kernel memory). (CVE-2018-7755)

Update instructions

The problem can be corrected by updating your system to the following package versions:

Ubuntu 16.04

After a standard system update you need to reboot your computer to make
all the necessary changes.

ATTENTION: Due to an unavoidable ABI change the kernel updates have
been given a new version number, which requires you to recompile and
reinstall all third party kernel modules you might have installed.
Unless you manually uninstalled the standard kernel metapackages
(e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
linux-powerpc), a standard system upgrade will automatically perform
this as well.