USN-974-2: Linux kernel regression

USN-974-1 fixed vulnerabilities in the Linux kernel. The fixes for CVE-2010-2240 caused failures for Xen hosts. This update fixes the problem. We apologize for the inconvenience. Original advisory details: Gael Delalleu, Rafal Wojtczuk, and Brad Spengler discovered that the memory manager did not properly handle when applications grow stacks into adjacent memory regions. A local attacker could exploit this to gain control of certain applications, potentially leading to privilege escalation, as demonstrated in attacks against the X server. (CVE-2010-2240) Kees Cook discovered that under certain situations the ioctl subsystem for DRM did not properly sanitize its arguments. A local attacker could exploit this to read previously freed kernel memory, leading to a loss of privacy. (CVE-2010-2803) Ben Hawkes discovered an integer overflow in the Controller Area Network (CAN) subsystem when setting up frame content and filtering certain messages. An attacker could send specially crafted CAN traffic to crash the system or gain root privileges. (CVE-2010-2959)