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             AUSCERT External Security Bulletin Redistribution

                  USN-5086-1: Linux kernel vulnerability
                             23 September 2021


        AusCERT Security Bulletin Summary

Product:           Linux Kernel
Publisher:         Ubuntu
Operating System:  Ubuntu
Impact/Access:     Administrator Compromise        -- Existing Account
                   Execute Arbitrary Code/Commands -- Existing Account
                   Denial of Service               -- Existing Account
Resolution:        Patch/Upgrade

Original Bulletin: 

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USN-5086-1: Linux kernel vulnerability
22 September 2021

IBM s390x systems could be made to crash or run programs as an

  o Ubuntu 21.04
  o Ubuntu 20.04 LTS
  o Ubuntu 18.04 LTS
  o Ubuntu 16.04 ESM


  o linux - Linux kernel
  o linux-hwe - Linux hardware enablement (HWE) kernel
  o linux-hwe-5.11 - Linux hardware enablement (HWE) kernel
  o linux-hwe-5.4 - Linux hardware enablement (HWE) kernel


Johan Almbladh discovered that the eBPF JIT implementation for IBM
s390x systems in the Linux kernel miscompiled operations in some
situations, allowing circumvention of the BPF verifier. A local
attacker could use this to cause a denial of service (system crash)
or possibly execute arbitrary code.

Update instructions

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

Ubuntu 21.04

  o linux-image-virtual -
  o linux-image-generic-64k -
  o linux-image-generic -
  o linux-image-oem-20.04 -
  o linux-image-5.11.0-36-lowlatency - 5.11.0-36.40
  o linux-image-5.11.0-36-generic - 5.11.0-36.40
  o linux-image-5.11.0-36-generic-64k - 5.11.0-36.40
  o linux-image-5.11.0-36-generic-lpae - 5.11.0-36.40
  o linux-image-generic-lpae -
  o linux-image-lowlatency -

Ubuntu 20.04

  o linux-image-5.4.0-86-generic-lpae - 5.4.0-86.97
  o linux-image-virtual -
  o linux-image-virtual-hwe-20.04 -
  o linux-image-generic -
  o linux-image-oem -
  o linux-image-lowlatency-hwe-20.04 -
  o linux-image-5.4.0-86-lowlatency - 5.4.0-86.97
  o linux-image-generic-hwe-20.04 -
  o linux-image-5.11.0-36-lowlatency - 5.11.0-36.40~20.04.1
  o linux-image-5.11.0-36-generic - 5.11.0-36.40~20.04.1
  o linux-image-5.11.0-36-generic-64k - 5.11.0-36.40~20.04.1
  o linux-image-5.11.0-36-generic-lpae - 5.11.0-36.40~20.04.1
  o linux-image-oem-osp1 -
  o linux-image-generic-lpae-hwe-20.04 -
  o linux-image-generic-64k-hwe-20.04 -
  o linux-image-generic-lpae -
  o linux-image-5.4.0-86-generic - 5.4.0-86.97
  o linux-image-lowlatency -

Ubuntu 18.04

  o linux-image-generic-hwe-18.04 -
  o linux-image-snapdragon-hwe-18.04 -
  o linux-image-5.4.0-86-generic-lpae - 5.4.0-86.97~18.04.1
  o linux-image-generic -
  o linux-image-oem -
  o linux-image-oem-osp1 -
  o linux-image-generic-lpae-hwe-18.04 -
  o linux-image-4.15.0-158-generic - 4.15.0-158.166
  o linux-image-5.4.0-86-lowlatency - 5.4.0-86.97~18.04.1
  o linux-image-4.15.0-158-generic-lpae - 4.15.0-158.166
  o linux-image-virtual -
  o linux-image-virtual-hwe-18.04 -
  o linux-image-4.15.0-158-lowlatency - 4.15.0-158.166
  o linux-image-lowlatency-hwe-18.04 -
  o linux-image-generic-lpae -
  o linux-image-5.4.0-86-generic - 5.4.0-86.97~18.04.1
  o linux-image-lowlatency -

Ubuntu 16.04

  o linux-image-virtual -
    Available with UA Infra or UA Desktop
  o linux-image-generic -
    Available with UA Infra or UA Desktop
  o linux-image-oem -
    Available with UA Infra or UA Desktop
  o linux-image-lowlatency-hwe-16.04 -
    Available with UA Infra or UA Desktop
  o linux-image-4.15.0-158-generic - 4.15.0-158.166~16.04.1
    Available with UA Infra or UA Desktop
  o linux-image-4.15.0-158-lowlatency - 4.15.0-158.166~16.04.1
    Available with UA Infra or UA Desktop
  o linux-image-4.4.0-216-lowlatency - 4.4.0-216.249
    Available with UA Infra or UA Desktop
  o linux-image-4.4.0-216-generic - 4.4.0-216.249
    Available with UA Infra or UA Desktop
  o linux-image-generic-hwe-16.04 -
    Available with UA Infra or UA Desktop
  o linux-image-virtual-hwe-16.04 -
    Available with UA Infra or UA Desktop
  o linux-image-lowlatency -
    Available with UA Infra or UA Desktop

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.


  o https://launchpad.net/bugs/1943960

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