USN-3160-2: Linux kernel (Trusty HWE) vulnerabilities

USN-3160-1 fixed vulnerabilities in the Linux kernel for Ubuntu 14.04 LTS. This update provides the corresponding updates for the Linux Hardware Enablement (HWE) kernel from Ubuntu 14.04 LTS for Ubuntu 12.04 LTS. CAI Qian discovered that shared bind mounts in a mount namespace exponentially added entries without restriction to the Linux kernel's mount table. A local attacker could use this to cause a denial of service (system crash). (CVE-2016-6213) It was discovered that a race condition existed in the procfs environread function in the Linux kernel, leading to an integer underflow. A local attacker could use this to expose sensitive information (kernel memory). (CVE-2016-7916)