RHSA-2018:2785: Important: kernel security and bug fix update

The kernel packages contain the Linux kernel, the core of any Linux operating system.<br>Security Fix(es):<br><li> 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)</li> <li> 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)</li> <li> kernel: mm: use-after-free in dogetmempolicy function allows local DoS or other unspecified impact (CVE-2018-10675)</li> 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.<br>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.<br>Bug Fix(es):<br><li> On systems running Red Hat Enterprise Linux 7 with Red Hat OpenShift Container Platform 3.5, a node sometimes got into "NodeNotReady" state after a CPU softlockup. Consequently, the node was not available. This update fixes an irq latency source in memory compaction. As a result, nodes no longer get into "NodeNotReady" state under the described circumstances. (BZ#1596281)</li> <li> Previously, the kernel source code was missing support to report the Speculative Store Bypass Disable (SSBD) vulnerability status on IBM Power Systems and the little-endian variants of IBM Power Systems. As a consequence, the /sys/devices/system/cpu/vulnerabilities/specstorebypass file incorrectly reported "Not affected" on both CPU architectures. 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#1612351)</li> <li> The hypervisors of Red Hat Enterprise Linux 7 virtual machines (VMs) in certain circumstances mishandled the microcode update in the kernel. As a consequence, the VMs sometimes became unresponsive when booting. This update applies an upstream patch to avoid early microcode update when running under a hypervisor. As a result, kernel hangs no longer occur in the described scenario. (BZ#1618388)</li>