[USN-3718-2] Linux kernel (HWE) regression

[Steve Beattie]

==========================================================================
Ubuntu Security Notice USN-3718-2
July 21, 2018

linux-hwe, linux-azure, linux-gcp regression
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 16.04 LTS

Summary:

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

Software Description:
- 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 LTS:
  linux-image-4.15.0-1014-gcp     4.15.0-1014.14~16.04.1
  linux-image-4.15.0-1018-azure   4.15.0-1018.18~16.04.1
  linux-image-4.15.0-29-generic   4.15.0-29.31~16.04.1
  linux-image-4.15.0-29-generic-lpae  4.15.0-29.31~16.04.1
  linux-image-4.15.0-29-lowlatency  4.15.0-29.31~16.04.1
  linux-image-azure               4.15.0.1018.24
  linux-image-gcp                 4.15.0.1014.26
  linux-image-generic-hwe-16.04   4.13.0.45.64
  linux-image-generic-lpae-hwe-16.04  4.13.0.45.64
  linux-image-gke                 4.15.0.1014.26
  linux-image-lowlatency-hwe-16.04  4.13.0.45.64

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.

References:
  https://usn.ubuntu.com/usn/usn-3718-2
  https://usn.ubuntu.com/usn/usn-3718-1
  https://launchpad.net/bugs/1779827, https://usn.ubuntu.com/usn/usn-3695-2

Package Information:
  https://launchpad.net/ubuntu/+source/linux-azure/4.15.0-1018.18~16.04.1
  https://launchpad.net/ubuntu/+source/linux-gcp/4.15.0-1014.14~16.04.1
  https://launchpad.net/ubuntu/+source/linux-hwe/4.15.0-29.31~16.04.1

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