Updated Linux kernel packages has been released for Ubuntu Linux 14.04 LTS to address a regression introduced by the previous update

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Ubuntu Security Notice USN-3741-3
August 17, 2018

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

- Ubuntu 14.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux: Linux kernel

Details:

USN-3741-1 introduced mitigations in the Linux kernel for Ubuntu 14.04
LTS 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)

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 14.04 LTS:
linux-image-3.13.0-156-generic 3.13.0-156.206
linux-image-3.13.0-156-generic-lpae 3.13.0-156.206
linux-image-3.13.0-156-lowlatency 3.13.0-156.206
linux-image-3.13.0-156-powerpc-e500 3.13.0-156.206
linux-image-3.13.0-156-powerpc-e500mc 3.13.0-156.206
linux-image-3.13.0-156-powerpc-smp 3.13.0-156.206
linux-image-3.13.0-156-powerpc64-emb 3.13.0-156.206
linux-image-3.13.0-156-powerpc64-smp 3.13.0-156.206
linux-image-generic 3.13.0.156.166
linux-image-generic-lpae 3.13.0.156.166
linux-image-lowlatency 3.13.0.156.166
linux-image-powerpc-e500 3.13.0.156.166
linux-image-powerpc-e500mc 3.13.0.156.166
linux-image-powerpc-smp 3.13.0.156.166
linux-image-powerpc64-emb 3.13.0.156.166
linux-image-powerpc64-smp 3.13.0.156.166

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-3741-3
https://usn.ubuntu.com/usn/usn-3741-1
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1787127, https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1787258

Package Information:
https://launchpad.net/ubuntu/+source/linux/3.13.0-156.206

  Linux kernel Regression Update for Ubuntu 14.04