Red Hat 5.6 EUS RHSA-2012:0358-01 Important: Kernel Security Issues

The kernel packages contain the Linux kernel, the core of any Linux operating system.
This update fixes the following security issues:
* Using PCI passthrough without interrupt remapping support allowed Xen hypervisor guests to generate MSI interrupts and thus potentially inject traps. A privileged guest user could use this flaw to crash the host or possibly escalate their privileges on the host. The fix for this issue can prevent PCI passthrough working and guests starting. Refer to Red Hat Bugzilla bug 715555 for details. (CVE-2011-1898, Important)
* IPv6 fragment identification value generation could allow a remote attacker to disrupt a target system's networking, preventing legitimate users from accessing its services. (CVE-2011-2699, Important)
* Using the SG_IO ioctl to issue SCSI requests to partitions or LVM volumes resulted in the requests being passed to the underlying block device. If a privileged user only had access to a single partition or LVM volume, they could use this flaw to bypass those restrictions and gain read and write access (and be able to issue other SCSI commands) to the entire block device. Refer to Red Hat Knowledgebase article 67869, linked to in the References, for further details about this issue. (CVE-2011-4127, Important)
* A flaw was found in the way the Linux kernel handled robust list pointersof user-space held futexes across exec() calls. A local, unprivileged user could use this flaw to cause a denial of service or, eventually, escalate their privileges. (CVE-2012-0028, Important)
* A missing boundary check was found in the Linux kernel's HFS file system implementation. A local attacker could use this flaw to cause a denial of service or escalate their privileges by mounting a specially-crafted disk. (CVE-2011-4330, Moderate)
Red Hat would like to thank Fernando Gont for reporting CVE-2011-2699, and Clement Lecigne for reporting CVE-2011-4330.
This update also fixes the following bugs:
* Previously, all timers for a Xen fully-virtualized domain were based on the time stamp counter (TSC) of the underlying physical CPU. This could cause observed time to go backwards on some hosts. This update moves all timers except HPET to the Xen monotonic system time, which fixes the bug as long as the HPET is removed from the configuration of the domain. (BZ#773359)
* Previously, tests of the Microsoft Server Virtualization Validation Program (SVVP) detected unreliability of the emulated HPET (High Performance Event Timer) on some hosts. Now, HPET can be configured as a per-domain configuration option; if it is disabled, the guest chooses a more reliable timer source. Disabling HPET is suggested for Windows guests, as well as fully-virtualized Linux guests that show occasional "time went backwards" errors in the console. (BZ#773360)
* SG_IO ioctls were not implemented correctly in the Red Hat Enterprise Linux 5 virtio-blk driver. Sending an SG_IO ioctl request to a virtio-blk disk caused the sending thread to enter an uninterruptible sleep state ("D" state). With this update, SG_IO ioctls are rejected by the virtio-blk driver; the ioctl system call simply returns an ENOTTY ("Inappropriate ioctl for device") error and the thread continues normally. (BZ#784658)
Users should upgrade to these updated packages, which contain backported patches to correct these issues. The system must be rebooted for this update to take effect.