(RHSA-2016:0103) Important: kernel security, bug fix, and enhancement update

The kernel packages contain the Linux kernel, the core of any Linux
operating system.

• It was found that the x86 ISA (Instruction Set Architecture) is prone to
  a denial of service attack inside a virtualized environment in the form of
  an infinite loop in the microcode due to the way (sequential) delivering of
  benign exceptions such as #DB (debug exception) is handled. A privileged
  user inside a guest could use this flaw to create denial of service
  conditions on the host kernel. (CVE-2015-8104, Important)

• A use-after-free flaw was found in the way the Linux kernel’s key
  management subsystem handled keyring object reference counting in certain
  error path of the join_session_keyring() function. A local, unprivileged
  user could use this flaw to escalate their privileges on the system.
  (CVE-2016-0728, Important)

• It was found that the fix for CVE-2015-1805 incorrectly kept buffer
  offset and buffer length in sync on a failed atomic read, potentially
  resulting in a pipe buffer state corruption. A local, unprivileged user
  could use this flaw to crash the system or leak kernel memory to user
  space. (CVE-2016-0774, Moderate)

Red Hat would like to thank the Perception Point research team for
reporting the CVE-2016-0728 issue. The security impact of the CVE-2016-0774
issue was discovered by Red Hat.

Bug fixes:

• NMI watchdog of guests using legacy LVT0-based NMI delivery did not work
  with APICv. Now, NMI works with LVT0 regardless of APICv. (BZ#1244726)

• Parallel file-extending direct I/O writes could previously race to update
  the size of the file. If they executed out-of-order, the file size could
  move backwards and push a previously completed write beyond the end of the
  file, causing it to be lost. (BZ#1258942)

• The GHES NMI handler had a global spin lock that significantly increased
  the latency of each perf sample collection. This update simplifies locking
  inside the handler. (BZ#1280200)

• Sometimes, iptables rules are updated along with ip rules, and routes are
  reloaded. Previously, skb->sk was mistakenly attached to some IPv6
  forwarding traffic packets, which could cause kernel panic. Now, such
  packets are checked and not processed. (BZ#1281700)

• The NUMA node was not reported for PCI adapters, which affected every
  POWER system deployed with Red Hat Enterprise Linux 7 and caused
  significant decrease in the system performance. (BZ#1283525)

• Processing packets with a lot of different IPv6 source addresses caused
  the kernel to return warnings concerning soft-lockups due to high lock
  contention and latency increase. (BZ#1285369)

• Running edge triggered interrupts with an ack notifier when
  simultaneously reconfiguring the Intel I/O IOAPIC did not work correctly,
  so EOI in the interrupt did not cause a VM to exit if APICv was enabled.
  Consequently, the VM sometimes became unresponsive. (BZ#1287001)

• Block device readahead was artificially limited, so the read performance
  was poor, especially on RAID devices. Now, per-device readahead limits are
  used for each device, which has improved read performance. (BZ#1287548)

• Identical expectations could not be tracked simultaneously even if they
  resided in different connection tracking zones. Now, an expectation insert
  attempt is rejected only if the zone is also identical. (BZ#1290093)

• The storvsc kernel driver for Microsoft Hyper-V storage was setting
  incorrect SRB flags, and Red Hat Enterprise Linux 7 guests running on
  Microsoft Hyper-V were experiencing slow I/O as well as I/O failures when
  they were connected to a virtual SAN. Now, SRB flags are set correctly.
  (BZ#1290095)

• When a NUMA system with no memory in node 0 was used, the system
  terminated unexpectedly during boot or when using OpenVSwitch. Now, the
  kernel tries to allocate memory from other nodes when node 0 is not
  present. (BZ#1300950)

Enhancement:

• IPsec has been updated to provide many fixes and some enhancements.
  Of particular note is the ability to match on outgoing interfaces.
  (BZ#1287407)