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=====================================================================
                   Red Hat Security Advisory

Synopsis:          Important: kernel-rt security and bug fix update
Advisory ID:       RHSA-2017:0931-01
Product:           Red Hat Enterprise Linux
Advisory URL:      https://access.redhat.com/errata/RHSA-2017:0931
Issue date:        2017-04-12
CVE Names:         CVE-2016-8650 CVE-2016-9793 CVE-2017-2618 
                   CVE-2017-2636 
=====================================================================

1. Summary:

An update for kernel-rt is now available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having a security impact
of Important. A Common Vulnerability Scoring System (CVSS) base score,
which gives a detailed severity rating, is available for each vulnerability
from the CVE link(s) in the References section.

2. Relevant releases/architectures:

Red Hat Enterprise Linux Realtime (v. 7) - noarch, x86_64
Red Hat Enterprise Linux for Real Time for NFV (v. 7) - noarch, x86_64

3. Description:

The kernel-rt packages provide the Real Time Linux Kernel, which enables
fine-tuning for systems with extremely high determinism requirements.

Security Fix(es):

* A race condition flaw was found in the N_HLDC Linux kernel driver when
accessing n_hdlc.tbuf list that can lead to double free. A local,
unprivileged user able to set the HDLC line discipline on the tty device
could use this flaw to increase their privileges on the system.
(CVE-2017-2636, Important)

* A flaw was found in the Linux kernel key management subsystem in which a
local attacker could crash the kernel or corrupt the stack and additional
memory (denial of service) by supplying a specially crafted RSA key. This
flaw panics the machine during the verification of the RSA key.
(CVE-2016-8650, Moderate)

* A flaw was found in the Linux kernel's implementation of setsockopt for
the SO_{SND|RCV}BUFFORCE setsockopt() system call. Users with non-namespace
CAP_NET_ADMIN are able to trigger this call and create a situation in which
the sockets sendbuff data size could be negative. This could adversely
affect memory allocations and create situations where the system could
crash or cause memory corruption. (CVE-2016-9793, Moderate)

* A flaw was found in the Linux kernel's handling of clearing SELinux
attributes on /proc/pid/attr files. An empty (null) write to this file can
crash the system by causing the system to attempt to access unmapped kernel
memory. (CVE-2017-2618, Moderate)

Red Hat would like to thank Alexander Popov for reporting CVE-2017-2636 and
Ralf Spenneberg for reporting CVE-2016-8650. The CVE-2017-2618 issue was
discovered by Paul Moore (Red Hat Engineering).

Bug Fix(es):

* Previously, a cgroups data structure was sometimes corrupted due to a
race condition in the kernel-rt cgroups code. Consequently, several system
tasks were blocked, and the operating system became unresponsive. This
update adds a lock that prevents the race condition. As a result, the
cgroups data structure no longer gets corrupted and the operating system no
longer hangs under the described circumstances. (BZ#1420784)

* The kernel-rt packages have been upgraded to the 3.10.0-514.16.1 source
tree, which provides a number of bug fixes over the previous version.
(BZ#1430749)

4. Solution:

For details on how to apply this update, which includes the changes
described in this advisory, refer to:

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

The system must be rebooted for this update to take effect.

5. Bugs fixed (https://bugzilla.redhat.com/):

1395187 - CVE-2016-8650 kernel: Null pointer dereference via keyctl
1402013 - CVE-2016-9793 kernel: Signed overflow for SO_{SND|RCV}BUFFORCE
1419916 - CVE-2017-2618 kernel: Off-by-one error in selinux_setprocattr (/proc/self/attr/fscreate)
1428319 - CVE-2017-2636 kernel: Race condition access to n_hdlc.tbuf causes double free in n_hdlc_release()
1430749 - kernel-rt: update to the RHEL7.3.z batch#4 source tree [RT-7.3.z]

6. Package List:

Red Hat Enterprise Linux for Real Time for NFV (v. 7):

Source:
kernel-rt-3.10.0-514.16.1.rt56.437.el7.src.rpm

noarch:
kernel-rt-doc-3.10.0-514.16.1.rt56.437.el7.noarch.rpm

x86_64:
kernel-rt-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debug-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debug-debuginfo-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debug-devel-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debug-kvm-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debug-kvm-debuginfo-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debuginfo-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debuginfo-common-x86_64-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-devel-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-kvm-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-kvm-debuginfo-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-trace-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-trace-debuginfo-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-trace-devel-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-trace-kvm-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-trace-kvm-debuginfo-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm

Red Hat Enterprise Linux Realtime (v. 7):

Source:
kernel-rt-3.10.0-514.16.1.rt56.437.el7.src.rpm

noarch:
kernel-rt-doc-3.10.0-514.16.1.rt56.437.el7.noarch.rpm

x86_64:
kernel-rt-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debug-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debug-debuginfo-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debug-devel-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debuginfo-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-debuginfo-common-x86_64-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-devel-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-trace-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-trace-debuginfo-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm
kernel-rt-trace-devel-3.10.0-514.16.1.rt56.437.el7.x86_64.rpm

These packages are GPG signed by Red Hat for security.  Our key and
details on how to verify the signature are available from
https://access.redhat.com/security/team/key/

7. References:

https://access.redhat.com/security/cve/CVE-2016-8650
https://access.redhat.com/security/cve/CVE-2016-9793
https://access.redhat.com/security/cve/CVE-2017-2618
https://access.redhat.com/security/cve/CVE-2017-2636
https://access.redhat.com/security/updates/classification/#important

8. Contact:

The Red Hat security contact is <secalert@redhat.com>. More contact
details at https://access.redhat.com/security/team/contact/

Copyright 2017 Red Hat, Inc.
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