7.1 - USN-3718-2

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