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             AUSCERT External Security Bulletin Redistribution

                 USN-4950-1: Linux kernel vulnerabilities
                                12 May 2021


        AusCERT Security Bulletin Summary

Product:           kernel
Publisher:         Ubuntu
Operating System:  Ubuntu
                   Linux variants
Impact/Access:     Execute Arbitrary Code/Commands -- Existing Account
                   Denial of Service               -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-3491 CVE-2021-3490 CVE-2021-3489

Original Bulletin: 

Comment: This advisory references vulnerabilities in the Linux kernel that 
         also affect distributions other than Ubuntu. It is recommended that
         administrators running Linux check for an updated version of the 
         kernel for their system.

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USN-4950-1: Linux kernel vulnerabilities
11 May 2021

Several security issues were fixed in the Linux kernel.

  o Ubuntu 21.04


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


Ryota Shiga discovered that the eBPF implementation in the Linux kernel did
not properly verify that a BPF program only reserved as much memory for a
ring buffer as was allocated. A local attacker could use this to cause a
denial of service (system crash) or execute arbitrary code. ( CVE-2021-3489 )

Manfred Paul discovered that the eBPF implementation in the Linux kernel
did not properly track bounds on bitwise operations. A local attacker could
use this to cause a denial of service (system crash) or execute arbitrary
code. ( CVE-2021-3490 )

Billy Jheng Bing-Jhong discovered that the io_uring implementation of the
Linux kernel did not properly enforce the MAX_RW_COUNT limit in some
situations. A local attacker could use this to cause a denial of service
(system crash) or execute arbitrary code. ( CVE-2021-3491 )

Norbert Slusarek discovered that the CAN ISOTP protocol implementation
in the Linux kernel contained a race condition. A local attacker could
use this to cause a denial of service (system crash) or possibly
execute arbitrary code. Please note that to address this issue,
SF_BROADCAST support was removed temporarily from the CAN ISOTP
implementation in Ubuntu 21.04 kernels. (LP: #1927409)

Update instructions

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

Ubuntu 21.04

  o linux-image-5.11.0-17-generic-64k - 5.11.0-17.18
  o linux-image-gke -
  o linux-image-5.11.0-17-generic-lpae - 5.11.0-17.18
  o linux-image-5.11.0-1007-gcp - 5.11.0-1007.7
  o linux-image-5.11.0-17-generic - 5.11.0-17.18
  o linux-image-5.11.0-1006-oracle - 5.11.0-1006.6
  o linux-image-oracle -
  o linux-image-5.11.0-17-lowlatency - 5.11.0-17.18
  o linux-image-azure -
  o linux-image-raspi-nolpae -
  o linux-image-virtual -
  o linux-image-raspi -
  o linux-image-5.11.0-1008-raspi - 5.11.0-1008.8
  o linux-image-generic-64k -
  o linux-image-generic -
  o linux-image-5.11.0-1008-raspi-nolpae - 5.11.0-1008.8
  o linux-image-aws -
  o linux-image-kvm -
  o linux-image-5.11.0-1005-azure - 5.11.0-1005.5
  o linux-image-generic-lpae -
  o linux-image-gcp -
  o linux-image-5.11.0-1007-aws - 5.11.0-1007.7
  o linux-image-lowlatency -
  o linux-image-5.11.0-1007-kvm - 5.11.0-1007.7

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 CVE-2021-3489
  o CVE-2021-3490
  o CVE-2021-3491
  o https://launchpad.net/bugs/1927409

Related notices

  o USN-4948-1 : linux-oem-5.10, linux-image-5.10.0-1026-oem,
  o USN-4949-1 : linux-hwe-5.8, linux-image-generic-64k, linux-image-gke,
    linux-image-5.8.0-53-generic, linux-image-raspi-nolpae,
    linux-image-5.8.0-1027-kvm, linux-image-kvm, linux-image-gcp,
    linux-image-generic-64k-hwe-20.04, linux-image-oem-20.04,
    linux-image-5.8.0-1032-azure, linux-image-5.8.0-1024-raspi-nolpae,
    linux-image-raspi, linux-image-generic-lpae, linux,
    linux-image-generic-lpae-hwe-20.04, linux-image-virtual-hwe-20.04,
    linux-gcp, linux-image-5.8.0-53-lowlatency, linux-raspi, linux-image-aws,
    linux-image-generic, linux-image-lowlatency-hwe-20.04, linux-image-virtual,
    linux-image-5.8.0-1024-raspi, linux-image-5.8.0-53-generic-lpae, linux-aws,
    linux-image-5.8.0-1033-aws, linux-kvm, linux-image-5.8.0-1029-oracle,
    linux-azure, linux-image-generic-hwe-20.04, linux-image-oracle,
    linux-image-5.8.0-53-generic-64k, linux-oracle, linux-image-5.8.0-1031-gcp,
    linux-image-azure, linux-image-lowlatency

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