RHSA-2018:2789: Important: kernel-rt security and bug fix update

First published: Tue Sep 25 2018(Updated: )

The kernel-rt packages provide the Real Time Linux Kernel, which enables fine-tuning for systems with extremely high determinism requirements.<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 tcp_collapse_ofo_queue() and tcp_prune_ofo_queue() 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> Red Hat would like to thank Juha-Matti Tilli (Aalto University - Department of Communications and Networking and Nokia Bell Labs) for reporting this issue.<br>Bug Fix(es):<br><li> The kernel-rt packages have been upgraded to the 3.10.0-693.39.1 source tree, which provides a number of bug fixes over the previous version. (BZ#1616431)</li> <li> Previously, preemption was enabled too early after a context switch. If a task was migrated to another CPU after a context switch, a mismatch between CPU and runqueue during load balancing sometimes occurred. Consequently, a runnable task on an idle CPU failed to run, and the operating system became unresponsive. This update disables preemption in the schedule_tail() function. As a result, CPU migration during post-schedule processing no longer occurs, which prevents the above mismatch. The operating system no longer hangs due to this bug. (BZ#1618466)</li>

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