RHSA-2018:2791: 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 SegmentSmack was found in the way the Linux kernel handled specially crafted TCP packets. A remote attacker could use this flaw to trigger time and calculation expensive calls to tcpcollapseofoqueue() and tcppruneofoqueue() functions by sending specially modified packets within ongoing TCP sessions which could lead to a CPU saturation and hence a denial of service on the system. Maintaining the denial of service condition requires continuous two-way TCP sessions to a reachable open port, thus the attacks cannot be performed using spoofed IP addresses. (CVE-2018-5390) 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 dogetmempolicy function allows local DoS or other unspecified impact (CVE-2018-10675) 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-2018-5390 and CVE-2018-5391.Bug Fix(es): 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 "maxsmtthreads()" function has been fixed. As a result, both threads are now detected correctly in the described situation. (BZ#1625330)