A Linux kernel security update has been released for Ubuntu 14.04 ESM, 16.04 LTS, 18.04 LTS, and 20.04 LTS,

LSN-0075-1: Linux kernel vulnerability

Linux kernel vulnerabilities

A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 18.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 ESM

Summary

Several security issues were fixed in the kernel.

Software Description

- linux - Linux kernel
- linux-aws - Linux kernel for Amazon Web Services (AWS) systems - linux-azure - Linux kernel for Microsoft Azure Cloud systems - linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems - linux-gke - Linux kernel for Google Container Engine (GKE) systems - linux-gkeop - Linux kernel for Google Container Engine (GKE) systems - linux-oem - Linux kernel for OEM systems

Details

Piotr Krysiuk discovered that the BPF subsystem in the Linux kernel did not properly apply speculative execution limits on some pointer types. A local attacker could use this to expose sensitive information (kernel memory). (CVE-2020-27170)

Piotr Krysiuk discovered that the BPF subsystem in the Linux kernel did not properly compute a speculative execution limit on pointer arithmetic in some situations. A local attacker could use this to expose sensitive information (kernel memory). (CVE-2020-27171)

Jann Horn discovered that a race condition existed in the madvise implementation in the Linux kernel, leading to a use-after-free vulnerability. A local attacker could use this to cause a denial of service (system crash). (CVE-2020-29372)

It was discovered that the memory management subsystem in the Linux kernel did not properly handle copy-on-write operations in some situations. A local attacker could possibly use this to gain unintended write access to read-only memory pages. (CVE-2020-29374)

De4dCr0w of 360 Alpha Lab discovered that the BPF verifier in the Linux kernel did not properly handle mod32 destination register truncation when the source register was known to be 0. A local attacker could use this to expose sensitive information (kernel memory) or possibly execute arbitrary code. (CVE-2021-3444)

Adam Nichols discovered that the iSCSI subsystem in the Linux kernel did not properly restrict access to iSCSI transport handles. A local attacker could use this to cause a denial of service or expose sensitive information (kernel pointer addresses). (CVE-2021-27363)

Adam Nichols discovered that an out-of-bounds read existed in the iSCSI subsystem in the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or expose sensitive information (kernel memory). (CVE-2021-27364)

Adam Nichols discovered that heap overflows existed in the iSCSI subsystem in the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2021-27365)

Update instructions

The problem can be corrected by updating your kernel livepatch to the following versions:

Ubuntu 18.04 LTS
aws - 75.2
generic - 75.2
gke - 75.2
gkeop - 75.2
lowlatency - 75.2
oem - 75.2

Ubuntu 20.04 LTS
aws - 75.2
azure - 75.2
gcp - 75.2
generic - 75.2
gke - 75.2
gkeop - 75.2
lowlatency - 75.2

Ubuntu 16.04 LTS
aws - 75.3
azure - 75.2
generic - 75.3
lowlatency - 75.3

Ubuntu 14.04 ESM
generic - 75.3
lowlatency - 75.3

Support Information

Kernels older than the levels listed below do not receive livepatch updates. If you are running a kernel version earlier than the one  listed below, please upgrade your kernel as soon as possible.
Ubuntu 18.04 LTS
linux-aws - 4.15.0-1054
linux-gke-4.15 - 4.15.0-1076
linux-gke-5.4 - 5.4.0-1009
linux-gkeop-5.4 - 5.4.0-1007
linux-hwe-5.4 - 5.4.0-26
linux-oem - 4.15.0-1063
linux - 4.15.0-69

Ubuntu 20.04 LTS
linux-aws - 5.4.0-1009
linux-azure - 5.4.0-1010
linux-gcp - 5.4.0-1009
linux-gke - 5.4.0-1033
linux-gkeop - 5.4.0-1009
linux-oem - 5.4.0-26
linux - 5.4.0-26

Ubuntu 16.04 LTS
linux-aws - 4.4.0-1098
linux-azure - 4.15.0-1063
linux-hwe - 4.15.0-69
linux - 4.4.0-168

Ubuntu 14.04 ESM
linux-lts-xenial - 4.4.0-168

References

- CVE-2020-27170
- CVE-2020-27171
- CVE-2020-29372
- CVE-2020-29374
- CVE-2021-3444
- CVE-2021-27363
- CVE-2021-27364
- CVE-2021-27365