arch/powerpc/perf/core-book3s.c in the Linux kernel before 5.12.13, on systems with perf_event_paranoid=-1 and no specific PMU driver support registered, allows local users to cause a denial of service (perf_instruction_pointer NULL pointer dereference and OOPS) via a "perf record" command.
https://github.com/torvalds/linux/commit/60b7ed54a41b550d50caf7f2418db4a7e75b5bdc
https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.12.13