RHSA-2016:0103 - Security Advisory

Topic

Updated kernel packages that fix three security issues, multiple bugs, and
one enhancement are now available for Red Hat Enterprise Linux 7.1 Extended
Update Support.

Red Hat Product Security has rated this update as having Important security
impact. Common Vulnerability Scoring System (CVSS) base scores, which give
detailed severity ratings, are available for each vulnerability from the
CVE links in the References section.

Description

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)

Solution

All kernel users are advised to upgrade to these updated packages, which
contain backported patches to correct these issues and add this
enhancement. The system must be rebooted for this update to take effect.

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.1 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.1 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.1 ppc64
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.1 ppc64le
• Red Hat Enterprise Linux EUS Compute Node 7.1 x86_64

Fixes

• BZ - 1278496 - CVE-2015-8104 virt: guest to host DoS by triggering an infinite loop in microcode via #DB exception
• BZ - 1297475 - CVE-2016-0728 kernel: Possible use-after-free vulnerability in keyring facility
• BZ - 1303961 - CVE-2016-0774 kernel: pipe buffer state corruption after unsuccessful atomic read from pipe

CVEs

• CVE-2015-8104
• CVE-2016-0728
• CVE-2016-0774

References

• http://www.redhat.com/security/updates/classification/#normal