[LSN-0083-1] Linux kernel vulnerability

Linux kernel vulnerabilities
A security issue affects these releases of Ubuntu and its derivatives:
– Ubuntu 20.04 LTS – Ubuntu 18.04 LTS – Ubuntu 16.04 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
The BPF subsystem in the Linux kernel before 4.17 mishandles situations with a long jump over an instruction sequence where inner instructions require substantial expansions into multiple BPF instructions, leading to an overflow. This affects kernel/bpf/core.c and net/core/filter.c. (CVE-2018-25020)
Maxim Levitsky discovered that the KVM hypervisor implementation for AMD processors in the Linux kernel did not properly prevent a guest VM from enabling AVIC in nested guest VMs. An attacker in a guest VM could use this to write to portions of the host’s physical memory. (CVE-2021-3653)
Nadav Amit discovered that the hugetlb implementation in the Linux kernel did not perform TLB flushes under certain conditions. A local attacker could use this to leak or alter data from other processes that use huge pages. (CVE-2021-4002)
Andy Nguyen discovered that the netfilter subsystem in the Linux kernel contained an out-of-bounds write in its setsockopt() implementation. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2021-22555)
It was discovered that the virtual file system implementation in the Linux kernel contained an unsigned to signed integer conversion error. A local attacker could use this to cause a denial of service (system crash) or execute arbitrary code. (CVE-2021-33909)
Update instructions
The problem can be corrected by updating your kernel livepatch to the following versions:
Ubuntu 20.04 LTS aws – 83.1 azure – 83.1 gcp – 83.1 generic – 83.1 gke – 83.1 gkeop – 83.1 lowlatency – 83.1
Ubuntu 18.04 LTS aws – 83.1 generic – 83.1 gke – 83.1 gke – 83.2 gkeop – 83.1 gkeop – 83.2 lowlatency – 83.1 oem – 83.1
Ubuntu 16.04 ESM aws – 83.1 azure – 83.1 generic – 83.1 lowlatency – 83.1
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 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 18.04 LTS linux-aws – 4.15.0-1054 linux-azure-4.15 – 4.15.0-1115 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 16.04 ESM linux-aws – 4.4.0-1098 linux-azure – 4.15.0-1063 linux-hwe – 4.15.0-143 linux – 4.4.0-168
Ubuntu 14.04 ESM linux-lts-xenial – 4.4.0-168
References
– CVE-2018-25020 – CVE-2021-3653 – CVE-2021-4002 – CVE-2021-22555 – CVE-2021-33909