Scientific Linux Security Update : kernel on SL6.x i386/x86_64

This script is Copyright (C) 2016 Tenable Network Security, Inc.

Synopsis :

The remote Scientific Linux host is missing one or more security

Description :

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

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.

See also :

Solution :

Update the affected packages.

Risk factor :

Medium / CVSS Base Score : 5.8

Family: Scientific Linux Local Security Checks

Nessus Plugin ID: 93096 ()

Bugtraq ID:

CVE ID: CVE-2016-5696

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