https://help.ubuntu.com/community/UbuntuStudio/RealTimeKerne...
> Security Implications
> All it would take is one malicious process to execute and take advantage of the real-time code to completely lock-out a user from their machine, turning that machine into part of a botnet or other malicious purpose. Real-Time processes have the potential to completely take-over a machine. This is the number one reason Ubuntu does not carry a Real-Time kernel.
The page goes on:
> A patch does exist to enable process to have real-time process access to any process requesting it.
According to the sched(7) man page, this has never been the case: before 2.6.12, the process had to have CAP_SYS_NICE; after, it was limited by policy through RLIMIT_RTPRIO. I guess it's possible that this was not the case for the original out-of-tree patch set.
But it's been there for many years, well before the 2020 edit that added the bulk of the current text on that wiki page.
There seems to be a pretty big leap from beginning of that sentence to the end, I personally wouldn't consider local DoS a problem.