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)
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