On Sat, 03 Apr 2021 09:02:26 +0200, John Wood said:
Currently, the scenario you propose is fully mitigated :). And notifying to userspace that all the tasks has been killed by "Brute" not decrease the security. It adds the possibility that the supervisor adopts the correct policy.
So how do you figure out how far up the chain you kill processes? What does a triple or quadruple fork do? How do you ensure that you deliver the notification to the correct supervisor? (Hint - walking backwards until you hit a process running as root isn't necessarily the right answer, especially once you consider containers and systems where gdm runs as non-root and other weird stuff..) Bonus points if you deal correctly with abuse of LD_PRELOAD to front-end a signal handler that catches SIGSEGV, without breaking the semantics of legitimate signal handlers...