UAF in all Linux kernels before 2/17/2017, but upgrading kernels is easier said than done for 99.9% of prod envs: seclists.org/oss-sec/2017/q1…

pointless when stuff like __ro_after_init and now refcount_t can go in despite being bad engineering...

I don't share your "bad engineering" opinion, and I think your involvement wouldn't be pointless at all.