Ubuntu Security Notice 5073-2 - 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. 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. Various other issues were also addressed.
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Ubuntu Security Notice USN-5073-2
September 17, 2021
linux-gcp, linux-gcp-4.15 vulnerabilities
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A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 18.04 LTS
- Ubuntu 16.04 ESM
Summary:
Several security issues were fixed in the Linux kernel.
Software Description:
- linux-gcp-4.15: Linux kernel for Google Cloud Platform (GCP) systems
- linux-gcp: Linux kernel for Google Cloud Platform (GCP) 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)
Norbert Slusarek discovered that the CAN broadcast manger (bcm) protocol
implementation in the Linux kernel did not properly initialize memory in
some situations. A local attacker could use this to expose sensitive
information (kernel memory). (CVE-2021-34693)
Murray McAllister discovered that the joystick device interface in the
Linux kernel did not properly validate data passed via an ioctl(). A local
attacker could use this to cause a denial of service (system crash) or
possibly execute arbitrary code on systems with a joystick device
registered. (CVE-2021-3612)
It was discovered that the Virtio console implementation in the Linux
kernel did not properly validate input lengths in some situations. A local
attacker could possibly use this to cause a denial of service (system
crash). (CVE-2021-38160)
Update instructions:
The problem can be corrected by updating your system to the following
package versions:
Ubuntu 18.04 LTS:
linux-image-4.15.0-1108-gcp 4.15.0-1108.122
linux-image-gcp-lts-18.04 4.15.0.1108.127
Ubuntu 16.04 ESM:
linux-image-4.15.0-1108-gcp 4.15.0-1108.122~16.04.1
linux-image-gcp 4.15.0.1108.109
linux-image-gke 4.15.0.1108.109
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:
https://ubuntu.com/security/notices/USN-5073-2
https://ubuntu.com/security/notices/USN-5073-1
CVE-2021-34693, CVE-2021-3612, CVE-2021-3653, CVE-2021-3656,
CVE-2021-38160
Package Information:
https://launchpad.net/ubuntu/+source/linux-gcp-4.15/4.15.0-1108.122