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USN-3878-3: Linux kernel regression

8 February 2019

USN-3878-1 introduced a regression in the Linux kernel.



  • linux - Linux kernel
  • linux-hwe - Linux hardware enablement (HWE) kernel


USN-3878-1 fixed vulnerabilities in the Linux kernel. Unfortunately,
that update introduced a regression that could prevent systems with
certain graphics chipsets from booting. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

It was discovered that a race condition existed in the vsock address family
implementation of the Linux kernel that could lead to a use-after-free
condition. A local attacker in a guest virtual machine could use this to
expose sensitive information (host machine kernel memory). (CVE-2018-14625)

Cfir Cohen discovered that a use-after-free vulnerability existed in the
KVM implementation of the Linux kernel, when handling interrupts in
environments where nested virtualization is in use (nested KVM
virtualization is not enabled by default in Ubuntu kernels). A local
attacker in a guest VM could possibly use this to gain administrative
privileges in a host machine. (CVE-2018-16882)

Wei Wu discovered that the KVM implementation in the Linux kernel did not
properly ensure that ioapics were initialized. A local attacker could use
this to cause a denial of service (system crash). (CVE-2018-19407)

It was discovered that the crypto subsystem of the Linux kernel leaked
uninitialized memory to user space in some situations. A local attacker
could use this to expose sensitive information (kernel memory).

Update instructions

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

Ubuntu 18.10
Ubuntu 18.04

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.