Oracle Linux: CVE-2019-19922: ELSA-2020-1769: kernel security, bug fix, and enhancement update (IMPORTANT) (Multiple Advisories)

Description

kernel/sched/fair.c in the Linux kernel before 5.3.9, when cpu.cfs_quota_us is used (e.g., with Kubernetes), allows attackers to cause a denial of service against non-cpu-bound applications by generating a workload that triggers unwanted slice expiration, aka CID-de53fd7aedb1. (In other words, although this slice expiration would typically be seen with benign workloads, it is possible that an attacker could calculate how many stray requests are required to force an entire Kubernetes cluster into a low-performance state caused by slice expiration, and ensure that a DDoS attack sent that number of stray requests. An attack does not affect the stability of the kernel; it only causes mismanagement of application execution.) A flaw was found in the Linux kernel’s scheduler, where it can allow attackers to cause a denial of service against non-CPU-bound applications by generating a workload that triggers unwanted scheduling slice expiration. A local attacker who can trigger a specific workload type could abuse this technique to trigger a system to be seen as degraded, and possibly trigger workload-rebalance in systems that use the slice-expiration metric as a measure of system health.