6.8 - RHSA-2013:0928

Problem Description:

Updated kernel packages that fix multiple security issues and several bugs are now available for Red Hat Enterprise Linux 6.3 Extended Update Support.

The Red Hat Security Response Team has rated this update as having important security impact. Common Vulnerability Scoring System (CVSS) base scores, which give detailed severity ratings, are available for each vulnerability from the CVE links in the References section.

2. Relevant releases/architectures:

Red Hat Enterprise Linux Server EUS (v. 6.3) - i386, noarch, ppc64, s390x, x86_64 Red Hat Enterprise Linux Server Optional EUS (v. 6.3) - i386, ppc64, s390x, x86_64

3. Description:

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 vhost kernel module handled descriptors that spanned multiple regions. A privileged guest user in a KVM (Kernel-based Virtual Machine) guest could use this flaw to crash the host or, potentially, escalate their privileges on the host. (CVE-2013-0311, Important)

* A buffer overflow flaw was found in the way UTF-8 characters were converted to UTF-16 in the utf8s_to_utf16s() function of the Linux kernel's FAT file system implementation. A local user able to mount a FAT file system with the "utf8=1" option could use this flaw to crash the system or, potentially, to escalate their privileges. (CVE-2013-1773, Important)

* A flaw was found in the way KVM handled guest time updates when the buffer the guest registered by writing to the MSR_KVM_SYSTEM_TIME machine state register (MSR) crossed a page boundary. A privileged guest user could use this flaw to crash the host or, potentially, escalate their privileges, allowing them to execute arbitrary code at the host kernel level. (CVE-2013-1796, Important)

* A potential use-after-free flaw was found in the way KVM handled guest time updates when the GPA (guest physical address) the guest registered by writing to the MSR_KVM_SYSTEM_TIME machine state register (MSR) fell into a movable or removable memory region of the hosting user-space process (by default, QEMU-KVM) on the host. If that memory region is deregistered from KVM using KVM_SET_USER_MEMORY_REGION and the allocated virtual memory reused, a privileged guest user could potentially use this flaw to escalate their privileges on the host. (CVE-2013-1797, Important)

* A flaw was found in the way KVM emulated IOAPIC (I/O Advanced Programmable Interrupt Controller). A missing validation check in the ioapic_read_indirect() function could allow a privileged guest user to crash the host, or read a substantial portion of host kernel memory. (CVE-2013-1798, 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 use-after-free flaw was found in the tmpfs implementation. A local user able to mount and unmount a tmpfs file system could use this flaw to cause a denial of service or, potentially, escalate their privileges. (CVE-2013-1767, Low)

* A format string flaw was found in the ext3_msg() function in the Linux kernel's ext3 file system implementation. A local user who is able to mount an ext3 file system could use this flaw to cause a denial of service or, potentially, escalate their privileges. (CVE-2013-1848, Low)

Red Hat would like to thank Andrew Honig of Google for reporting the CVE-2013-1796, CVE-2013-1797, and CVE-2013-1798 issues. The CVE-2012-4542 issue was discovered by Paolo Bonzini of Red Hat.

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. The system must be rebooted for this update to take effect.

4. Solution:

Before applying this update, make sure all previously-released errata relevant to your system have been applied.

This update is available via the Red Hat Network. Details on how to use the Red Hat Network to apply this update are available at https://access.redhat.com/knowledge/articles/11258

To install kernel packages manually, use "rpm -ivh [package]". Do not use "rpm -Uvh" as that will remove the running kernel binaries from your system. You may use "rpm -e" to remove old kernels after determining that the new kernel functions properly on your system.

5. Bugs fixed (http://bugzilla.redhat.com/):

875360 - CVE-2012-4542 kernel: block: default SCSI command filter does not accomodate commands overlap across device classes 912905 - CVE-2013-0311 kernel: vhost: fix length for cross region descriptor 915592 - CVE-2013-1767 Kernel: tmpfs: fix use-after-free of mempolicy object 916115 - CVE-2013-1773 kernel: VFAT slab-based buffer overflow 917012 - CVE-2013-1796 kernel: kvm: buffer overflow in handling of MSR_KVM_SYSTEM_TIME 917013 - CVE-2013-1797 kernel: kvm: after free issue with the handling of MSR_KVM_SYSTEM_TIME 917017 - CVE-2013-1798 kernel: kvm: out-of-bounds access in ioapic indirect register reads 920783 - CVE-2013-1848 kernel: ext3: format string issues