A soft lockup caused by running uncontrolled concurrent warn_alloc() calls when running LTP memcg_stress test was found. Bug report: https://www.spinics.net/lists/linux-mm/msg128248.html
Created kernel tracking bugs for this issue: Affects: fedora-all [bug 1492665]
Soft lockup during stress testing is very common. This would fall under DOS at best, I'm not convinced that we should chase up all softlockups to their security case as these can be very, very common on misconfigured systems, or people misconfiguring during benchmarking / overloading. I'd say we'd get 5-10 of these a week in support and I wouldn't have the bandwidth to chase them down. In this case it seems the cgroup operations are being abused.
This problem not only allows a local unprivileged user to intentionally lockup the system but also allows some non stress test workload to by chance lockup. This problem was addressed upstream as https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=400e22499dd92613821374c8c6c88c7225359980 . Please be sure to backport to RHEL8 if using 4.9+ kernel.