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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.
(BZ#1353827)
- 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. (BZ#1353828)
- 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. (BZ#1343894)
- 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.
(BZ#1355980)
- 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. (BZ#1355981)
- 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. (BZ#1347539)
- 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. (BZ#1348062)
Bugs fixed (https://bugzilla.redhat.com/):
1354708 - CVE-2016-5696 kernel: challenge ACK counter information disclosure.
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