What circumstances are needed for this to be exploitable? Wondering if iptables could mitigate for systems where upgrading the kernel is non-trivial.
(Many of the results are for code like language runtimes and debugging tools that don't actually use recvmmsg() themselves)
tl;dr looks like it'd function well a local privilege exploit. not an expert, but as a remote exploit think it would need 1) a service running recvmmsg (which is kind of unlikely) 2) a way to cause recvmsg to error, and 3) a way to cause the service to close its socket in the middle of the recvmmsg call.
I was just starting to look into this since people were claiming it was pretty severe and yet I hadn't seen any POC's. Have you made any more progress?
For whatever my opinion is worth (i.e. not much), I would agree with you that remote exploitation of this particular bug would be really difficult.