RHSA-2017:0892 - Security Advisory

Topic

An update for kernel is now available for Red Hat Enterprise Linux 6.

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 packages contain the Linux kernel, the core of any Linux operating system.

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's implementation of seq_file where a local attacker could manipulate memory in the put() function pointer. This could lead to memory corruption and possible privileged escalation. (CVE-2016-7910, Moderate)

Red Hat would like to thank Alexander Popov for reporting CVE-2017-2636.

Bug Fix(es):

• Previously, Chelsio firmware included an incorrectly-formatted firmware bin file. As a consequence, the firmware could not be flashed. This update provides a firmware bin file that is formatted correctly. As a result, Chelsio firmware can now be flashed successfully. (BZ#1433865)
• When multiple simultaneous processes attempted to read from the /proc/stat file, spinlock overhead was generated on Non-Uniform Memory Access (NUMA) systems. Consequently, a large amount of CPU was consumed. With this update, the underlying source code has been fixed to avoid taking spinlock when the interrupt line does not exist. As a result, the spinlock overhead is now generated less often, and multiple simultaneous processes can now read /proc/stat without consuming a large amount of CPU. (BZ#1428106)

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 Server 6 x86_64
• Red Hat Enterprise Linux Server 6 i386
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 6 i386
• Red Hat Enterprise Linux Workstation 6 x86_64
• Red Hat Enterprise Linux Workstation 6 i386
• Red Hat Enterprise Linux Desktop 6 x86_64
• Red Hat Enterprise Linux Desktop 6 i386
• Red Hat Enterprise Linux for IBM z Systems 6 s390x
• Red Hat Enterprise Linux for Power, big endian 6 ppc64
• Red Hat Enterprise Linux for Scientific Computing 6 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 6 s390x

Fixes

• BZ - 1399727 - CVE-2016-7910 kernel: Use after free in seq file
• BZ - 1428319 - CVE-2017-2636 kernel: Race condition access to n_hdlc.tbuf causes double free in n_hdlc_release()

CVEs

• CVE-2016-7910
• CVE-2017-2636

References

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