USN-3597-2: Linux kernel (HWE) vulnerabilities

USN-3597-1 fixed vulnerabilities in the Linux kernel for Ubuntu 17.10. This update provides the corresponding updates for the Linux Hardware Enablement (HWE) kernel from Ubuntu 17.10 for Ubuntu 16.04 LTS. USNS 3541-2 and 3523-2 provided mitigations for Spectre and Meltdown (CVE-2017-5715, CVE-2017-5753, CVE-2017-5754) for the i386, amd64, and ppc64el architectures for Ubuntu 16.04 LTS. This update provides the corresponding mitigations for the arm64 architecture. Original advisory details: Jann Horn discovered that microprocessors utilizing speculative execution and indirect branch prediction may allow unauthorized memory reads via sidechannel attacks. This flaw is known as Meltdown. A local attacker could use this to expose sensitive information, including kernel memory. (CVE-2017-5754) Jann Horn discovered that microprocessors utilizing speculative execution and branch prediction may allow unauthorized memory reads via sidechannel attacks. This flaw is known as Spectre. A local attacker could use this to expose sensitive information, including kernel memory. (CVE-2017-5715, CVE-2017-5753)