RHSA-2018:0152 - Security Advisory

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 flaw was found in the Linux kernel's key management system where it was possible for an attacker to escalate privileges or crash the machine. If a user key gets negatively instantiated, an error code is cached in the payload area. A negatively instantiated key may be then be positively instantiated by updating it with valid data. However, the ->update key type method must be aware that the error code may be there. (CVE-2015-8539, Important)
• It was found that fanout_add() in 'net/packet/af_packet.c' in the Linux kernel, before version 4.13.6, allows local users to gain privileges via crafted system calls that trigger mishandling of packet_fanout data structures, because of a race condition (involving fanout_add and packet_do_bind) that leads to a use-after-free bug. (CVE-2017-15649, Important)
• A vulnerability was found in the Linux kernel where the keyctl_set_reqkey_keyring() function leaks the thread keyring. This allows an unprivileged local user to exhaust kernel memory and thus cause a DoS. (CVE-2017-7472, Moderate)

Red Hat would like to thank Dmitry Vyukov of Google engineering for reporting CVE-2015-8539.

Bug Fix(es):

• The kernel-rt packages have been upgraded to 3.10.0-693.15.1 source tree, which provides a number of bug fixes over the previous version. (BZ#1519506)

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
• Red Hat Enterprise Linux for Real Time for x86_64 - Extended Life Cycle Support 7 x86_64

Fixes

• BZ - 1284450 - CVE-2015-8539 kernel: local privesc in key management
• BZ - 1442086 - CVE-2017-7472 kernel: keyctl_set_reqkey_keyring() leaks thread keyrings
• BZ - 1504574 - CVE-2017-15649 kernel: Use-after-free in the af_packet.c
• BZ - 1519506 - kernel-rt: update to the RHEL7.4.z batch#4 source tree

CVEs

• CVE-2015-8539
• CVE-2017-7472
• CVE-2017-12192
• CVE-2017-12193
• CVE-2017-15649

References

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