(RHSA-2018:2925) Important: kernel security and bug fix update

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: 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, the kernel source code lacked support to report the Speculative Store Bypass Disable (SSBD) vulnerability status on IBM Power Systems. As a consequence, the /sys/devices/system/cpu/vulnerabilities/spec_store_bypass file incorrectly reported “Not affected”. This fix updates the kernel source code to properly report the SSBD status either as “Vulnerable” or “Mitigation: Kernel entry/exit barrier (TYPE)”, where TYPE is one of “eieio”, “hwsync”, “fallback”, or “unknown”. (BZ#1615873)

• After updating the system to prevent the L1 Terminal Fault (L1TF) vulnerability, only one thread was detected on systems that offer processing of two threads on a single processor core. With this update, the “__max_smt_threads()” function has been fixed. As a result, both threads are now detected correctly in the described situation. (BZ#1625335)

• 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#1629634)