RHSA-2018:3590 - Security Advisory

Topic

An update for kernel is now available for Red Hat Enterprise Linux 7.2 Advanced Update Support, Red Hat Enterprise Linux 7.2 Telco Extended Update Support, and Red Hat Enterprise Linux 7.2 Update Services for SAP Solutions.

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 flaw named FragmentSmack was found in the way the Linux kernel handled reassembly of fragmented IPv4 and IPv6 packets. A remote attacker could use this flaw to trigger time and calculation expensive fragment reassembly algorithm by sending specially crafted packets which could lead to a CPU saturation and hence a denial of service on the system. (CVE-2018-5391)
• kernel: out-of-bounds access in the show_timer function in kernel/time/posix-timers.c (CVE-2017-18344)
• kernel: mm: use-after-free in do_get_mempolicy function allows local DoS or other unspecified impact (CVE-2018-10675)
• kernel: Integer overflow in Linux's create_elf_tables function (CVE-2018-14634)

For more details about the security issue(s), including the impact, a CVSS score, and other related information, refer to the CVE page(s) listed in the References section.

Red Hat would like to thank Juha-Matti Tilli (Aalto University - Department of Communications and Networking and Nokia Bell Labs) for reporting CVE-2018-5391 and Qualys Research Labs for reporting CVE-2018-14634.

Bug Fix(es):

• Previously, a kernel panic occurred when the kernel tried to make an out of bound access to the array that describes the L1 Terminal Fault (L1TF) mitigation state on systems without Extended Page Tables (EPT) support. This update extends the array of mitigation states to cover all the states, which effectively prevents out of bound array access. Also, this update enables rejecting invalid, irrelevant values, that might be erroneously provided by the userspace. As a result, the kernel no longer panics in the described scenario. (BZ#1629565)
• Previously, a packet was missing the User Datagram Protocol (UDP) payload checksum during a full checksum computation, if the hardware checksum was not applied. As a consequence, a packet with an incorrect checksum was dropped by a peer. With this update, the kernel includes the UDP payload checksum during the full checksum computation. As a result, the checksum is computed correctly and the packet can be received by the peer. (BZ#1635792)
• Previously, a transform lookup through the xfrm framework could be performed on an already transformed destination cache entry (dst_entry). When using User Datagram Protocol (UDP) over IPv6 with a connected socket in conjunction with Internet Protocol Security (IPsec) in Encapsulating Security Payload (ESP) transport mode. As a consequence, invalid IPv6 fragments transmitted from the host or the kernel occasionally terminated unexpectedly due to a socket buffer (SKB) underrun. With this update, the xfrm lookup on an already transformed dst_entry is not possible. As a result, using UDP iperf utility over IPv6 ESP no longer causes invalid IPv6 fragment transmissions or a kernel panic. (BZ#1639586)

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 - AUS 7.2 x86_64
• Red Hat Enterprise Linux Server - TUS 7.2 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.2 x86_64

Fixes

• BZ - 1575065 - CVE-2018-10675 kernel: mm: use-after-free in do_get_mempolicy function allows local DoS or other unspecified impact
• BZ - 1609664 - CVE-2018-5391 kernel: IP fragments with random offsets allow a remote denial of service (FragmentSmack)
• BZ - 1610958 - CVE-2017-18344 kernel: out-of-bounds access in the show_timer function in kernel/time/posix-timers.c
• BZ - 1624498 - CVE-2018-14634 kernel: Integer overflow in Linux's create_elf_tables function

CVEs

• CVE-2017-18344
• CVE-2018-5391
• CVE-2018-10675
• CVE-2018-14634

References

• https://access.redhat.com/security/updates/classification/#important
• https://access.redhat.com/articles/3553061
• https://access.redhat.com/security/vulnerabilities/mutagen-astronomy