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USN-4917-1: Linux kernel vulnerabilities

15 April 2021

Several security issues were fixed in the Linux kernel.

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Releases

Packages

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)

Piotr Krysiuk discovered that the BPF JIT compiler for x86 in the Linux
kernel did not properly validate computation of branch displacements in
some situations. A local attacker could use this to cause a denial of
service (system crash) or possibly execute arbitrary code. (CVE-2021-29154)

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Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines.

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Update instructions

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

Ubuntu 20.10
Ubuntu 20.04
Ubuntu 18.04

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.

References

Related notices

  • USN-4915-1: linux-oem-5.6, linux-image-5.6.0-1054-oem, linux-image-oem-20.04
  • LSN-0077-1: gke-5.4, lowlatency-5.4, gcp, gkeop, gke, generic-5.4, gkeop-5.4
  • USN-4916-1: linux-image-azure-lts-18.04, linux-image-virtual, linux-oracle, linux-image-4.4.0-209-powerpc64-emb, linux-image-4.15.0-1101-snapdragon, linux-image-4.15.0-1113-azure, linux-image-4.4.0-1092-kvm, linux-image-azure, linux-image-4.4.0-209-lowlatency, linux-image-generic-lts-wily, linux-image-4.4.0-1127-aws, linux-image-generic-lpae-lts-xenial, linux-image-4.4.0-209-generic, linux-image-generic-hwe-16.04, linux-image-lowlatency, linux-image-4.4.0-209-powerpc64-smp, linux-image-4.4.0-1151-raspi2, linux-image-snapdragon, linux-image-4.4.0-209-generic-lpae, linux-image-generic-lpae-lts-vivid, linux-aws-hwe, linux-image-powerpc-e500mc-lts-xenial, linux-azure-4.15, linux-image-powerpc64-emb-lts-vivid, linux-image-4.15.0-142-generic-lpae, linux-image-generic-hwe-16.04-edge, linux-image-generic-lts-utopic, linux-image-powerpc64-smp-lts-vivid, linux-gcp-4.15, linux-azure, linux-image-4.15.0-1017-dell300x, linux-image-4.15.0-142-lowlatency, linux-image-powerpc-e500mc-lts-wily, linux-image-lowlatency-lts-wily, linux-image-4.15.0-1090-kvm, linux-image-generic-lts-xenial, linux-image-4.4.0-1155-snapdragon, linux-gcp, linux-image-powerpc-e500mc-lts-vivid, linux-image-lowlatency-lts-utopic, linux-image-oracle, linux-image-powerpc64-emb-lts-wily, linux-image-virtual-lts-vivid, linux, linux-image-4.15.0-1070-oracle, linux-image-powerpc-smp-lts-vivid, linux-image-powerpc64-smp-lts-wily, linux-image-powerpc-e500mc, linux-image-raspi2, linux-image-lowlatency-lts-xenial, linux-image-4.4.0-209-powerpc-smp, linux-image-powerpc-e500mc-lts-utopic, linux-image-generic-lpae-lts-utopic, linux-snapdragon, linux-image-virtual-lts-xenial, linux-aws, linux-image-azure-edge, linux-image-generic, linux-image-4.15.0-1099-aws, linux-image-gke, linux-image-lowlatency-lts-vivid, linux-image-generic-lts-vivid, linux-image-aws-hwe, linux-image-powerpc-smp-lts-wily, linux-image-4.4.0-209-powerpc-e500mc, linux-image-kvm, linux-image-generic-lpae-lts-wily, linux-image-virtual-hwe-16.04-edge, linux-image-virtual-lts-utopic, linux-image-oem, linux-image-lowlatency-hwe-16.04, linux-image-4.15.0-142-generic, linux-image-powerpc-smp-lts-xenial, linux-image-generic-lpae-hwe-16.04, linux-image-powerpc-smp, linux-image-4.15.0-1098-gcp, linux-dell300x, linux-image-lowlatency-hwe-16.04-edge, linux-image-generic-lpae, linux-image-4.15.0-1084-raspi2, linux-image-powerpc64-emb, linux-image-gcp-lts-18.04, linux-image-oracle-lts-18.04, linux-image-aws-lts-18.04, linux-kvm, linux-hwe, linux-image-4.4.0-1091-aws, linux-image-powerpc64-emb-lts-utopic, linux-image-virtual-hwe-16.04, linux-raspi2, linux-image-virtual-lts-wily, linux-image-powerpc64-smp-lts-utopic, linux-image-powerpc64-smp-lts-xenial, linux-image-powerpc-smp-lts-utopic, linux-image-dell300x, linux-image-powerpc64-emb-lts-xenial, linux-image-generic-lpae-hwe-16.04-edge, linux-image-powerpc64-smp, linux-image-aws, linux-lts-xenial, linux-image-gcp
  • LSN-0076-1: aws, gke-5.4, oem, lowlatency-4.4, lowlatency-5.4, gcp, gke-4.15, azure, gkeop, gke, generic-4.15, generic-5.4, gkeop-5.4, lowlatency-4.15, generic-4.4
  • USN-4912-1: linux-oem-5.6, linux-image-oem-20.04, linux-image-5.6.0-1053-oem

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