The kernel packages contain the Linux kernel, the core of any Linux operating system. This update fixes the following security issues: * A buffer overflow flaw was found in the way the Linux kernel"s XFS file system implementation handled links with overly long path names. A local, unprivileged user could use this flaw to cause a denial of service or escalate their privileges by mounting a specially-crafted disk. * Flaws in ghash_update and ghash_final could allow a local, unprivileged user to cause a denial of service. * A flaw was found in the Linux kernel"s Journaling Block Device . A local, unprivileged user could use this flaw to crash the system by mounting a specially-crafted ext3 or ext4 disk. * It was found that the kvm_vm_ioctl_assign_device function in the KVM subsystem of a Linux kernel did not check if the user requesting device assignment was privileged or not. A local, unprivileged user on the host could assign unused PCI devices, or even devices that were in use and whose resources were not properly claimed by the respective drivers, which could result in the host crashing. * Two flaws were found in the way the Linux kernel"s __sys_sendmsg function, when invoked via the sendmmsg system call, accessed user-space memory. A local, unprivileged user could use these flaws to cause a denial of service. * The RHSA-2011:1530 kernel update introduced an integer overflow flaw in the Linux kernel. On PowerPC systems, a local, unprivileged user could use this flaw to cause a denial of service. * A flaw was found in the way the KVM subsystem of a Linux kernel handled PIT IRQs when there was no virtual interrupt controller set up. A local, unprivileged user on the host could force this situation to occur, resulting in the host crashing. * A flaw was found in the way the Linux kernel"s XFS file system implementation handled on-disk Access Control Lists . A local, unprivileged user could use this flaw to cause a denial of service or escalate their privileges by mounting a specially-crafted disk. * A flaw was found in the way the Linux kernel"s KVM hypervisor implementation emulated the syscall instruction for 32-bit guests. An unprivileged guest user could trigger this flaw to crash the guest. * A divide-by-zero flaw was found in the Linux kernel"s igmp_heard_query function. An attacker able to send certain IGMP packets to a target system could use this flaw to cause a denial of service. Red Hat would like to thank Nick Bowler for reporting CVE-2011-4081; Sasha Levin for reporting CVE-2011-4347; Tetsuo Handa for reporting CVE-2011-4594; Maynard Johnson for reporting CVE-2011-4611; Wang Xi for reporting CVE-2012-0038; Stephan Barwolf for reporting CVE-2012-0045; and Simon McVittie for reporting CVE-2012-0207. Upstream acknowledges Mathieu Desnoyers as the original reporter of CVE-2011-4594. This update also fixes several bugs. Documentation for these changes will be available shortly from the Technical Notes document linked to in the References section. Users should upgrade to these updated packages, which contain backported patches to correct these issues, and fix the bugs noted in the Technical Notes. The system must be rebooted for this update to take effect.