The kernel packages contain the Linux kernel, the core of any Linux operating system. This update fixes the following security issues: * A flaw was found in the way the Xen hypervisor implementation handled instruction emulation during virtual machine exits. A malicious user-space process running in an SMP guest could trick the emulator into reading a different instruction than the one that caused the virtual machine to exit. An unprivileged guest user could trigger this flaw to crash the host. This only affects systems with both an AMD x86 processor and the AMD Virtualization extensions enabled. * A flaw allowed the tc_fill_qdisc function in the Linux kernel"s packet scheduler API implementation to be called on built-in qdisc structures. A local, unprivileged user could use this flaw to trigger a NULL pointer dereference, resulting in a denial of service. * A flaw was found in the way space was allocated in the Linux kernel"s Global File System 2 implementation. If the file system was almost full, and a local, unprivileged user made an fallocate request, it could result in a denial of service. Note: Setting quotas to prevent users from using all available disk space would prevent exploitation of this flaw. These updated kernel packages include a number of bug fixes and enhancements. Space precludes documenting all of these changes in this advisory. Refer to the Red Hat Enterprise Linux 5.7 Technical Notes for information about the most significant bug fixes and enhancements included in this update: https://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/5.7_Tech nical_Notes/kernel.html#RHSA-2011-1065 All Red Hat Enterprise Linux 5 users are advised to install these updated packages, which correct these issues. The system must be rebooted for this update to take effect.