USN-3653-2: Linux kernel (HWE) vulnerabilities

USN-3653-1 fixed vulnerabilities and added mitigations 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. Jann Horn and Ken Johnson discovered that microprocessors utilizing speculative execution of a memory read may allow unauthorized memory reads via a sidechannel attack. This flaw is known as Spectre Variant 4. A local attacker could use this to expose sensitive information, including kernel memory. (CVE-2018-3639) It was discovered that the netlink subsystem in the Linux kernel did not properly restrict observations of netlink messages to the appropriate net namespace. A local attacker could use this to expose sensitive information (kernel netlink traffic). (CVE-2017-17449) Tuba Yavuz discovered that a double-free error existed in the USBTV007 driver of the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2017-17975) It was discovered that a race condition existed in the Device Mapper component of the Linux kernel. A local attacker could use this to cause a denial of service (system crash). (CVE-2017-18203) It was discovered that an infinite loop could occur in the madvise(2) implementation in the Linux kernel in certain circumstances. A local attacker could use this to cause a denial of service (system hang). (CVE-2017-18208) Silvio Cesare discovered a buffer overwrite existed in the NCPFS implementation in the Linux kernel. A remote attacker controlling a malicious NCPFS server could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2018-8822)