[USN-5072-1] Linux kernel vulnerabilities

========================================================================== Ubuntu Security Notice USN-5072-1 September 08, 2021
linux-azure-5.8, linux-oem-5.10 vulnerabilities ==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:
– Ubuntu 20.04 LTS
Summary:
Several security issues were fixed in the Linux kernel.
Software Description: – linux-azure-5.8: Linux kernel for Microsoft Azure cloud systems – linux-oem-5.10: Linux kernel for OEM systems
Details:
Maxim Levitsky and Paolo Bonzini discovered that the KVM hypervisor implementation for AMD processors in the Linux kernel allowed a guest VM to disable restrictions on VMLOAD/VMSAVE in a nested guest. An attacker in a guest VM could use this to read or write portions of the host’s physical memory. (CVE-2021-3656)
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)
Update instructions:
The problem can be corrected by updating your system to the following package versions:
Ubuntu 20.04 LTS: linux-image-5.10.0-1045-oem 5.10.0-1045.47 linux-image-5.8.0-1041-azure 5.8.0-1041.44~20.04.1 linux-image-azure 5.8.0.1041.44~20.04.13 linux-image-oem-20.04 5.10.0.1045.47 linux-image-oem-20.04b 5.10.0.1045.47
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-5072-1 CVE-2021-3653, CVE-2021-3656
Package Information: launchpad.net/ubuntu/+source/linux-azure-5.8/5.8.0-1041.44~20.04.1 launchpad.net/ubuntu/+source/linux-oem-5.10/5.10.0-1045.47