Synopsis
Important: kernel-rt security and bug fix update
Type/Severity
Security Advisory: Important
Topic
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.
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)
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.
Affected Products
-
Red Hat Enterprise Linux for Real Time 7 x86_64
-
Red Hat Enterprise Linux for Real Time for NFV 7 x86_64
Fixes
- BZ - 1395187 - CVE-2016-8650 kernel: Null pointer dereference via keyctl
- BZ - 1402013 - CVE-2016-9793 kernel: Signed overflow for SO_{SND|RCV}BUFFORCE
- BZ - 1419916 - CVE-2017-2618 kernel: Off-by-one error in selinux_setprocattr (/proc/self/attr/fscreate)
- BZ - 1428319 - CVE-2017-2636 kernel: Race condition access to n_hdlc.tbuf causes double free in n_hdlc_release()
- BZ - 1430749 - kernel-rt: update to the RHEL7.3.z batch#4 source tree [RT-7.3.z]
CVEs
References
Vulmon