Synopsis:          Important: kernel security and bug fix update
Advisory ID:       SLSA-2016:1664-1
Issue Date:        2016-08-23
CVE Numbers:       CVE-2016-5696
--

Security Fix(es):

It was found that the RFC 5961 challenge ACK rate limiting as implemented
in the Linux kernel's networking subsystem allowed an off-path attacker to
leak certain information about a given connection by creating congestion
on the global challenge ACK rate limit counter and then measuring the
changes by probing packets. An off-path attacker could use this flaw to
either terminate TCP connection and/or inject payload into non-secured TCP
connection between two endpoints on the network. (CVE-2016-5696,
Important)

Bug Fix(es):

* When loading the Direct Rendering Manager (DRM) kernel module, the
kernel panicked if DRM was previously unloaded. The kernel panic was
caused by a memory leak of the ID Resolver (IDR2). With this update, IDR2
is loaded during kernel boot, and the kernel panic no longer occurs in the
described scenario.

* When more than one process attempted to use the "configfs" directory
entry at the same time, a kernel panic in some cases occurred. With this
update, a race condition between a directory entry and a lookup operation
has been fixed. As a result, the kernel no longer panics in the described
scenario.

* When shutting down the system by running the halt -p command, a kernel
panic occurred due to a conflict between the kernel offlining CPUs and the
sched command, which used the sched group and the sched domain data
without first checking the data. The underlying source code has been fixed
by adding a check to avoid the conflict. As a result, the described
scenario no longer results in a kernel panic.

* In some cases, running the ipmitool command caused a kernel panic due to
a race condition in the ipmi message handler. This update fixes the race
condition, and the kernel panic no longer occurs in the described
scenario.

* Previously, multiple Very Secure FTP daemon (vsftpd) processes on a
directory with a large number of files led to a high contention rate on
each inode's spinlock, which caused excessive CPU usage. With this update,
a spinlock to protect a single memory-to-memory copy has been removed from
the ext4_getattr() function. As a result, system CPU usage has been
reduced and is no longer excessive in the described situation.

* When the gfs2_grow utility is used to extend Global File System 2
(GFS2), the next block allocation causes the GFS2 kernel module to re-read
its resource group index. If multiple processes in the GFS2 module raced
to do the same thing, one process sometimes overwrote a valid object
pointer with an invalid pointer, which caused either a kernel panic or a
file system corruption. This update ensures that the resource group object
pointer is not overwritten. As a result, neither kernel panic nor file
system corruption occur in the described scenario.

* Previously, the SCSI Remote Protocol over InfiniBand (IB-SRP) was
disabled due to a bug in the srp_queue() function. As a consequence, an
attempt to enable the Remote Direct Memory Access (RDMA) at boot caused
the kernel to crash. With this update, srp_queue() has been fixed, and the
system now boots as expected when RDMA is enabled.

Enhancement(s):

* This update optimizes the efficiency of the Transmission Control
Protocol (TCP) when the peer is using a window under 537 bytes in size. As
a result, devices that use maximum segment size (MSS) of 536 bytes or
fewer will experience improved network performance.
--

SL6
  x86_64
    kernel-2.6.32-642.4.2.el6.x86_64.rpm
    kernel-debug-2.6.32-642.4.2.el6.x86_64.rpm
    kernel-debug-debuginfo-2.6.32-642.4.2.el6.i686.rpm
    kernel-debug-debuginfo-2.6.32-642.4.2.el6.x86_64.rpm
    kernel-debug-devel-2.6.32-642.4.2.el6.i686.rpm
    kernel-debug-devel-2.6.32-642.4.2.el6.x86_64.rpm
    kernel-debuginfo-2.6.32-642.4.2.el6.i686.rpm
    kernel-debuginfo-2.6.32-642.4.2.el6.x86_64.rpm
    kernel-debuginfo-common-i686-2.6.32-642.4.2.el6.i686.rpm
    kernel-debuginfo-common-x86_64-2.6.32-642.4.2.el6.x86_64.rpm
    kernel-devel-2.6.32-642.4.2.el6.x86_64.rpm
    kernel-headers-2.6.32-642.4.2.el6.x86_64.rpm
    perf-2.6.32-642.4.2.el6.x86_64.rpm
    perf-debuginfo-2.6.32-642.4.2.el6.i686.rpm
    perf-debuginfo-2.6.32-642.4.2.el6.x86_64.rpm
    python-perf-debuginfo-2.6.32-642.4.2.el6.i686.rpm
    python-perf-debuginfo-2.6.32-642.4.2.el6.x86_64.rpm
    python-perf-2.6.32-642.4.2.el6.x86_64.rpm
  i386
    kernel-2.6.32-642.4.2.el6.i686.rpm
    kernel-debug-2.6.32-642.4.2.el6.i686.rpm
    kernel-debug-debuginfo-2.6.32-642.4.2.el6.i686.rpm
    kernel-debug-devel-2.6.32-642.4.2.el6.i686.rpm
    kernel-debuginfo-2.6.32-642.4.2.el6.i686.rpm
    kernel-debuginfo-common-i686-2.6.32-642.4.2.el6.i686.rpm
    kernel-devel-2.6.32-642.4.2.el6.i686.rpm
    kernel-headers-2.6.32-642.4.2.el6.i686.rpm
    perf-2.6.32-642.4.2.el6.i686.rpm
    perf-debuginfo-2.6.32-642.4.2.el6.i686.rpm
    python-perf-debuginfo-2.6.32-642.4.2.el6.i686.rpm
    python-perf-2.6.32-642.4.2.el6.i686.rpm
  noarch
    kernel-abi-whitelists-2.6.32-642.4.2.el6.noarch.rpm
    kernel-doc-2.6.32-642.4.2.el6.noarch.rpm
    kernel-firmware-2.6.32-642.4.2.el6.noarch.rpm

- Scientific Linux Development Team