USN-3718-2: Linux kernel (HWE) regression
21 July 2018
linux-hwe, linux-azure, linux-gcp regression
A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 16.04 LTS
A regression that caused boot failures was fixed in the Linux kernel.
- 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
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)
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 - 184.108.40.2068.24
- linux-image-gcp - 220.127.116.114.26
- linux-image-generic-hwe-16.04 - 18.104.22.168.64
- linux-image-generic-lpae-hwe-16.04 - 22.214.171.124.64
- linux-image-gke - 126.96.36.1994.26
- linux-image-lowlatency-hwe-16.04 - 188.8.131.52.64
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
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.