USN-5091-3: Linux kernel (Azure) regression
15 October 2021
USN-5091-1 introduced a regression in the Linux kernel for Microsoft Azure cloud systems.
Releases
Packages
- linux-azure - Linux kernel for Microsoft Azure Cloud systems
- linux-azure-5.4 - Linux kernel for Microsoft Azure cloud systems
Details
USN-5091-1 fixed vulnerabilities in Linux 5.4-based kernels.
Unfortunately, for Linux kernels intended for use within Microsoft
Azure environments, that update introduced a regression that could
cause the kernel to fail to boot in large Azure instance types.
This update fixes the problem.
We apologize for the inconvenience.
Original advisory details:
Ofek Kirzner, Adam Morrison, Benedict Schlueter, and Piotr Krysiuk
discovered that the BPF verifier in the Linux kernel missed possible
mispredicted branches due to type confusion, allowing a side-channel
attack. An attacker could use this to expose sensitive information.
(CVE-2021-33624)
It was discovered that the tracing subsystem in the Linux kernel did not
properly keep track of per-cpu ring buffer state. A privileged attacker
could use this to cause a denial of service. (CVE-2021-3679)
Alexey Kardashevskiy discovered that the KVM implementation for PowerPC
systems in the Linux kernel did not properly validate RTAS arguments in
some situations. An attacker in a guest vm could use this to cause a denial
of service (host OS crash) or possibly execute arbitrary code.
(CVE-2021-37576)
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)
Michael Wakabayashi discovered that the NFSv4 client implementation in the
Linux kernel did not properly order connection setup operations. An
attacker controlling a remote NFS server could use this to cause a denial
of service on the client. (CVE-2021-38199)
It was discovered that the MAX-3421 host USB device driver in the Linux
kernel did not properly handle device removal events. A physically
proximate attacker could use this to cause a denial of service (system
crash). (CVE-2021-38204)
Update instructions
The problem can be corrected by updating your system to the following package versions:
Ubuntu 20.04
Ubuntu 18.04
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.