RHSA-2019:1489: 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> An integer overflow flaw was found in the way the Linux kernel's networking subsystem processed TCP Selective Acknowledgment (SACK) segments. While processing SACK segments, the Linux kernel's socket buffer (SKB) data structure becomes fragmented. Each fragment is about TCP maximum segment size (MSS) bytes. To efficiently process SACK blocks, the Linux kernel merges multiple fragmented SKBs into one, potentially overflowing the variable holding the number of segments. A remote attacker could use this flaw to crash the Linux kernel by sending a crafted sequence of SACK segments on a TCP connection with small value of TCP MSS, resulting in a denial of service (DoS). (CVE-2019-11477)</li> <li> kernel: Double free in lib/idr.c (CVE-2019-3896)</li> <li> Kernel: tcp: excessive resource consumption while processing SACK blocks allows remote denial of service (CVE-2019-11478)</li> <li> Kernel: tcp: excessive resource consumption for TCP connections with low MSS allows remote denial of service (CVE-2019-11479)</li> For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.<br>Bug Fix(es):<br><li> MDS mitigations not enabled on Intel Skylake CPUs (BZ#1713026)</li> <li> [RHEL6] mdclear flag missing from /proc/cpuinfo (BZ#1713029)</li> <li> RHEL6 kernel does not disable SMT with mds=full,nosmt (BZ#1713044)</li>