==========================================================================
Ubuntu Security Notice USN-3742-3
August 21, 2018

linux-lts-trusty regressions
==========================================================================

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

- Ubuntu 12.04 ESM

Summary:

USN-3742-2 introduced regressions in the Linux Hardware Enablement
(HWE) kernel for Ubuntu 12.04 ESM.

Software Description:
- linux-lts-trusty: Linux hardware enablement kernel from Trusty for Precise ESM

Details:

USN-3742-2 introduced mitigations in the Linux Hardware Enablement
(HWE) kernel for Ubuntu 12.04 ESM to address L1 Terminal Fault (L1TF)
vulnerabilities (CVE-2018-3620, CVE-2018-3646). Unfortunately, the
update introduced regressions that caused kernel panics when booting
in some environments as well as preventing Java applications from
starting. This update fixes the problems.

We apologize for the inconvenience.

Original advisory details:

 It was discovered that memory present in the L1 data cache of an Intel CPU
 core may be exposed to a malicious process that is executing on the CPU
 core. This vulnerability is also known as L1 Terminal Fault (L1TF). A local
 attacker in a guest virtual machine could use this to expose sensitive
 information (memory from other guests or the host OS). (CVE-2018-3646)

 It was discovered that memory present in the L1 data cache of an Intel CPU
 core may be exposed to a malicious process that is executing on the CPU
 core. This vulnerability is also known as L1 Terminal Fault (L1TF). A local
 attacker could use this to expose sensitive information (memory from the
 kernel or other processes). (CVE-2018-3620)

 Andrey Konovalov discovered an out-of-bounds read in the POSIX
 timers subsystem in the Linux kernel. A local attacker could use
 this to cause a denial of service (system crash) or expose sensitive
 information. (CVE-2017-18344)

 Juha-Matti Tilli discovered that the TCP implementation in the Linux kernel
 performed algorithmically expensive operations in some situations when
 handling incoming packets. A remote attacker could use this to cause a
 denial of service. (CVE-2018-5390)

 Juha-Matti Tilli discovered that the IP implementation in the Linux kernel
 performed algorithmically expensive operations in some situations when
 handling incoming packet fragments. A remote attacker could use this to
 cause a denial of service. (CVE-2018-5391)

Update instructions:

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

Ubuntu 12.04 ESM:
  linux-image-3.13.0-156-generic  3.13.0-156.206~precise1
  linux-image-3.13.0-156-generic-lpae  3.13.0-156.206~precise1
  linux-image-generic-lpae-lts-trusty  3.13.0.156.146
  linux-image-generic-lts-trusty  3.13.0.156.146

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-3742-3
  https://usn.ubuntu.com/usn/usn-3742-2
  https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1787127
  https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1787258
  https://wiki.ubuntu.com/SecurityTeam/KnowledgeBase/L1TF