[USN-4915-1] Linux kernel (OEM) vulnerabilities

[Steve Beattie]

==========================================================================
Ubuntu Security Notice USN-4915-1
April 15, 2021

linux-oem-5.6 vulnerabilities
==========================================================================

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

- Ubuntu 20.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-oem-5.6: Linux kernel for OEM systems

Details:

It was discovered that the overlayfs implementation in the Linux kernel did
not properly validate the application of file system capabilities with
respect to user namespaces. A local attacker could use this to gain
elevated privileges. (CVE-2021-3493)

Vincent Dehors discovered that the shiftfs file system in the Ubuntu Linux
kernel did not properly handle faults in copy_from_user() when passing
through ioctls to an underlying file system. A local attacker could use
this to cause a denial of service (memory exhaustion) or execute arbitrary
code. (CVE-2021-3492)

Update instructions:

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

Ubuntu 20.04 LTS:
  linux-image-5.6.0-1054-oem      5.6.0-1054.58
  linux-image-oem-20.04           5.6.0.1054.50

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-4915-1
  CVE-2021-3492, CVE-2021-3493

Package Information:
  https://launchpad.net/ubuntu/+source/linux-oem-5.6/5.6.0-1054.58

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