RHSA-2013:0928 - Security Advisory

Topic

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.

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.

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.

Affected Products

• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.3 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 6.3 i386
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 6.3 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 6.3 ppc64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.3 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support from RHUI 6.3 i386

Fixes

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

CVEs

• CVE-2013-0311
• CVE-2012-4542
• CVE-2013-1773
• CVE-2013-1798
• CVE-2013-1796
• CVE-2013-1797
• CVE-2013-1767
• CVE-2013-1848

References

• https://access.redhat.com/security/updates/classification/#important
• https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/6.3_Technical_Notes/kernel.html