The kernel packages contain the Linux kernel, the core of any Linux operating system.
This update fixes the following security issues:
A race condition was found in the way asynchronous I/O and fallocate() interacted when using the ext4 file system. A local, unprivileged user could use this flaw to expose random data from an extent whose data blocks have not yet been written, and thus contain data from a deleted file. (CVE-2012-4508, Important)
A flaw was found in the way the vhost kernel module handled descriptors that spanned multiple regions. A privileged guest user in a KVM guest could use this flaw to crash the host or, potentially, escalate their privileges on the host. (CVE-2013-0311, Important)
It was found that the default SCSI command filter does not accommodate commands that overlap across device classes. A privileged guest user could potentially use this flaw to write arbitrary data to a LUN that is passed-through as read-only. (CVE-2012-4542, Moderate)
A flaw was found in the way the xen_failsafe_callback() function in the Linux kernel handled the failed iret (interrupt return) instruction notification from the Xen hypervisor. An unprivileged user in a 32-bit para-virtualized guest could use this flaw to crash the guest. (CVE-2013-0190, Moderate)
A flaw was found in the way pmd_present() interacted with PROT_NONE memory ranges when transparent hugepages were in use. A local, unprivileged user could use this flaw to crash the system. (CVE-2013-0309, Moderate)
A flaw was found in the way CIPSO (Common IP Security Option) IP options were validated when set from user mode. A local user able to set CIPSO IP options on the socket could use this flaw to crash the system. (CVE-2013-0310, Moderate)
Red Hat would like to thank Theodore Ts'o for reporting CVE-2012-4508, and Andrew Cooper of Citrix for reporting CVE-2013-0190. Upstream acknowledges Dmitry Monakhov as the original reporter of CVE-2012-4508. The CVE-2012-4542 issue was discovered by Paolo Bonzini of Red Hat.
This update also fixes several hundred bugs and adds enhancements. Refer to the Red Hat Enterprise Linux 6.4 Release Notes for information on the most significant of these changes, and the Technical Notes for further information, both linked to in the References.
All Red Hat Enterprise Linux 6 users are advised to install these updated packages, which correct these issues, and fix the bugs and add the enhancements noted in the Red Hat Enterprise Linux 6.4 Release Notes and Technical Notes. The system must be rebooted for this update to take effect.