USN-4367-1: Linux kernel vulnerabilities

24 May 2020

Several security issues were fixed in the Linux kernel.



  • linux - Linux kernel
  • linux-aws - Linux kernel for Amazon Web Services (AWS) systems
  • linux-azure - Linux kernel for Microsoft Azure Cloud systems
  • linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems
  • linux-kvm - Linux kernel for cloud environments
  • linux-oracle - Linux kernel for Oracle Cloud systems
  • linux-raspi - Linux kernel for Raspberry Pi (V8) systems
  • linux-riscv - Linux kernel for RISC-V systems


It was discovered that the btrfs implementation in the Linux kernel did not
properly detect that a block was marked dirty in some situations. An
attacker could use this to specially craft a file system image that, when
unmounted, could cause a denial of service (system crash). (CVE-2019-19377)

It was discovered that the linux kernel did not properly validate certain
mount options to the tmpfs virtual memory file system. A local attacker
with the ability to specify mount options could use this to cause a denial
of service (system crash). (CVE-2020-11565)

It was discovered that the block layer in the Linux kernel contained a race
condition leading to a use-after-free vulnerability. A local attacker could
possibly use this to cause a denial of service (system crash) or execute
arbitrary code. (CVE-2020-12657)

Update instructions

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

Ubuntu 20.04

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.