(RHSA-2011:1321) Moderate: kernel security and bug fix update

The kernel packages contain the Linux kernel.

Security fix:

• A flaw in skb_gro_header_slow() in the Linux kernel could lead to GRO
  (Generic Receive Offload) fields being left in an inconsistent state. An
  attacker on the local network could use this flaw to trigger a denial of
  service. (CVE-2011-2723, Moderate)

Red Hat would like to thank Brent Meshier for reporting this issue.

Bug fixes:

• When reading a file from a subdirectory in /proc/bus/pci/ while
  hot-unplugging the device related to that file, the system will crash. Now,
  the kernel correctly handles the simultaneous removal of a device and
  access to the representation of that device in the proc file system.
  (BZ#713454)

• RHSA-2011:0017 introduced a regression: Non-disk SCSI devices (except for
  tape drives) such as enclosure or CD-ROM devices were hidden when attached
  to a SAS based RAID controller that uses the megaraid_sas driver. With this
  update, such devices are accessible, as expected. (BZ#726487)

• The fix for CVE-2010-3432 provided in RHSA-2011:0004 introduced a
  regression: Information in sctp_packet_config(), which was called before
  appending data chunks to a packet, was not reset, causing considerably poor
  SCTP (Stream Control Transmission Protocol) performance. With this update,
  the packet information is reset after transmission. (BZ#727591)

• Certain systems do not correctly set the ACPI FADT APIC mode bit. They
  set the bit to “cluster” mode instead of “physical” mode which caused these
  systems to boot without the TSC (Time Stamp Counter). With this update, the
  ACPI FADT check has been removed due to its unreliability. (BZ#728162)

• Performance when invalidating and rereading cached data as a glock moves
  around the cluster with GFS2 is improved. (BZ#729082)

• Performance issues occurred when multiple nodes attempted to call mmap()
  on the same inode at the same time on a GFS2 file system, as it was using
  an exclusive glock. With this update, a shared lock is used when “noatime”
  is set on the mount, allowing mmap() operations to occur in parallel,
  fixing this bug. Note that this issue only refers to mmap() system calls,
  and not to subsequent page faults. (BZ#729090)

• Some of the functions in the GFS2 file system were not reserving enough
  space for the resource group header in a transaction and for resource
  groups bit blocks that get added when a memory allocation is performed.
  That resulted in failed write and allocation operations. With this update,
  GFS2 makes sure to reserve space in the described scenario, using the new
  gfs2_rg_blocks() inline function. (BZ#729092)

• When GFS2 grew the file system, it never reread the rindex file during
  the grow. This is necessary for large grows when the file system is almost
  full, and GFS2 needs to use some of the space allocated earlier in the grow
  to complete it. Now, if GFS2 fails to reserve the necessary space and the
  rindex data is not up-to-date, it rereads it. (BZ#729094)

• Previously, when the Xen hypervisor split a 2 MB page into 4 KB pages, it
  linked the new page from PDE (Page Directory Entry) before it filled
  entries of the page with appropriate data. Consequently, when doing a live
  migration with EPT (Extended Page Tables) enabled on a non-idle guest
  running with more than two virtual CPUs, the guest often terminated
  unexpectedly. With this update, the Xen hypervisor prepares the page table
  entry first, and then links it in. (BZ#730684)

• Changes made to TSC as a clock source for IRQs caused virtual machines
  running under the VMware ESX or ESXi hypervisors to become unresponsive
  during the initial kernel boot process. With this update, the
  enable_tsc_timer flag enables the do_timer_tsc_timekeeping() function to be
  called in the do_timer_interrupt_hook() function, preventing a deadlock in
  the timer interrupt handler. (BZ#730688)

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.