(RHSA-2013:0928) Important: kernel security and bug fix update

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.