USN-3405-2: Linux kernel (Xenial HWE) vulnerabilities

USN-3405-1 fixed vulnerabilities in the Linux kernel for Ubuntu 16.04 LTS. This update provides the corresponding updates for the Linux Hardware Enablement (HWE) kernel from Ubuntu 16.04 LTS for Ubuntu 14.04 LTS. It was discovered that a use-after-free vulnerability existed in the POSIX message queue implementation in the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2017-11176) Huang Weller discovered that the ext4 filesystem implementation in the Linux kernel mishandled a needs-flushing-before-commit list. A local attacker could use this to expose sensitive information. (CVE-2017-7495) It was discovered that a buffer overflow existed in the Broadcom FullMAC WLAN driver in the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2017-7541) It was discovered that the Linux kernel did not honor the UEFI secure boot mode when performing a kexec operation. A local attacker could use this to bypass secure boot restrictions. (CVE-2015-7837)