RHSA-2017:0932 - Security Advisory

Topic

An update for kernel-rt is now available for Red Hat Enterprise MRG 2.

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 use-after-free flaw was found in the way the Linux kernel's Datagram Congestion Control Protocol (DCCP) implementation freed SKB (socket buffer) resources for a DCCP_PKT_REQUEST packet when the IPV6_RECVPKTINFO option is set on the socket. A local, unprivileged user could use this flaw to alter the kernel memory, allowing them to escalate their privileges on the system. (CVE-2017-6074, 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; Andrey Konovalov (Google) for reporting CVE-2017-6074; and Ralf Spenneberg for reporting CVE-2016-8650. The CVE-2017-2618 issue was discovered by Paul Moore (Red Hat Engineering).

Bug Fix(es):

• The kernel-rt packages have been upgraded to version 3.10.0-514.rt56.219, which provides a number of bug fix updates over the previous version. (BZ#1429613)

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

• MRG Realtime 2 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 - 1423071 - CVE-2017-6074 kernel: use after free in dccp protocol
• BZ - 1428319 - CVE-2017-2636 kernel: Race condition access to n_hdlc.tbuf causes double free in n_hdlc_release()
• BZ - 1429613 - update the MRG 2.5.z 3.10 kernel-rt sources

CVEs

• CVE-2016-8650
• CVE-2016-9793
• CVE-2017-2618
• CVE-2017-2636
• CVE-2017-6074

References

• https://access.redhat.com/security/updates/classification/#important