[USN-4910-1] Linux kernel vulnerabilities

========================================================================== Ubuntu Security Notice USN-4910-1 April 13, 2021
linux, linux-aws, linux-azure, linux-gcp, linux-hwe-5.8, linux-kvm, linux-oracle, linux-raspi vulnerabilities ==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:
– Ubuntu 20.10 – Ubuntu 20.04 LTS
Summary:
Several security issues were fixed in the Linux 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-kvm: Linux kernel for cloud environments – linux-oracle: Linux kernel for Oracle Cloud systems – linux-raspi: Linux kernel for Raspberry Pi (V8) systems – linux-hwe-5.8: Linux hardware enablement (HWE) kernel
Details:
Ryota Shiga discovered that the sockopt BPF hooks in the Linux kernel could allow a user space program to probe for valid kernel addresses. A local attacker could use this to ease exploitation of another kernel vulnerability. (CVE-2021-20239)
It was discovered that the BPF verifier in the Linux kernel did not properly handle signed add32 and sub integer overflows. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2021-20268)
It was discovered that the priority inheritance futex implementation in the Linux kernel contained a race condition, leading to a use-after-free vulnerability. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2021-3347)
It was discovered that the network block device (nbd) driver in the Linux kernel contained a use-after-free vulnerability during device setup. A local attacker with access to the nbd device could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2021-3348)
吴异 discovered that the NFS implementation in the Linux kernel did not properly prevent access outside of an NFS export that is a subdirectory of a file system. An attacker could possibly use this to bypass NFS access restrictions. (CVE-2021-3178)
Update instructions:
The problem can be corrected by updating your system to the following package versions:
Ubuntu 20.10: linux-image-5.8.0-1020-raspi 5.8.0-1020.23 linux-image-5.8.0-1020-raspi-nolpae 5.8.0-1020.23 linux-image-5.8.0-1023-kvm 5.8.0-1023.25 linux-image-5.8.0-1025-oracle 5.8.0-1025.26 linux-image-5.8.0-1027-azure 5.8.0-1027.29 linux-image-5.8.0-1027-gcp 5.8.0-1027.28 linux-image-5.8.0-1028-aws 5.8.0-1028.30 linux-image-5.8.0-49-generic 5.8.0-49.55 linux-image-5.8.0-49-generic-64k 5.8.0-49.55 linux-image-5.8.0-49-generic-lpae 5.8.0-49.55 linux-image-5.8.0-49-lowlatency 5.8.0-49.55 linux-image-aws 5.8.0.1028.30 linux-image-azure 5.8.0.1027.27 linux-image-gcp 5.8.0.1027.27 linux-image-generic 5.8.0.49.54 linux-image-generic-64k 5.8.0.49.54 linux-image-generic-lpae 5.8.0.49.54 linux-image-gke 5.8.0.1027.27 linux-image-kvm 5.8.0.1023.25 linux-image-lowlatency 5.8.0.49.54 linux-image-oem-20.04 5.8.0.49.54 linux-image-oracle 5.8.0.1025.24 linux-image-raspi 5.8.0.1020.23 linux-image-raspi-nolpae 5.8.0.1020.23 linux-image-virtual 5.8.0.49.54
Ubuntu 20.04 LTS: linux-image-5.8.0-49-generic 5.8.0-49.55~20.04.1 linux-image-5.8.0-49-generic-64k 5.8.0-49.55~20.04.1 linux-image-5.8.0-49-generic-lpae 5.8.0-49.55~20.04.1 linux-image-5.8.0-49-lowlatency 5.8.0-49.55~20.04.1 linux-image-generic-64k-hwe-20.04 5.8.0.49.55~20.04.33 linux-image-generic-hwe-20.04 5.8.0.49.55~20.04.33 linux-image-generic-lpae-hwe-20.04 5.8.0.49.55~20.04.33 linux-image-lowlatency-hwe-20.04 5.8.0.49.55~20.04.33 linux-image-virtual-hwe-20.04 5.8.0.49.55~20.04.33
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: ubuntu.com/security/notices/USN-4910-1 CVE-2021-20239, CVE-2021-20268, CVE-2021-3178, CVE-2021-3347, CVE-2021-3348
Package Information: launchpad.net/ubuntu/+source/linux/5.8.0-49.55 launchpad.net/ubuntu/+source/linux-aws/5.8.0-1028.30 launchpad.net/ubuntu/+source/linux-azure/5.8.0-1027.29 launchpad.net/ubuntu/+source/linux-gcp/5.8.0-1027.28 launchpad.net/ubuntu/+source/linux-kvm/5.8.0-1023.25 launchpad.net/ubuntu/+source/linux-oracle/5.8.0-1025.26 launchpad.net/ubuntu/+source/linux-raspi/5.8.0-1020.23 launchpad.net/ubuntu/+source/linux-hwe-5.8/5.8.0-49.55~20.04.1