=========================================================================Ubuntu Security Notice USN-4367-2
May 28, 2020
linux regression
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 20.04 LTS
Summary:
USN-4367-1 introduced a regression in the Linux kernel.
Software Description:
- linux: Linux kernel
Details:
USN-4367-1 fixed vulnerabilities in the 5.4 Linux kernel. Unfortunately,
that update introduced a regression in overlayfs. This update corrects
the problem.
We apologize for the inconvenience.
Original advisory details:
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 LTS:
linux-image-5.4.0-33-generic 5.4.0-33.37
linux-image-5.4.0-33-generic-lpae 5.4.0-33.37
linux-image-5.4.0-33-lowlatency 5.4.0-33.37
linux-image-generic 5.4.0.33.38
linux-image-generic-lpae 5.4.0.33.38
linux-image-lowlatency 5.4.0.33.38
linux-image-oem 5.4.0.33.38
linux-image-oem-osp1 5.4.0.33.38
linux-image-virtual 5.4.0.33.38
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://ubuntu.com/security/notices/USN-4367-2
https://ubuntu.com/security/notices/USN-4367-1
https://launchpad.net/bugs/1879690
Package Information:
https://launchpad.net/ubuntu/+source/linux/5.4.0-33.37
