That's a reoccurring pattern across Lennart software. He gets an idea of the way things should work, maybe from the spec or maybe just from his own subjective biases, and has his software expect things to work that way and fail when it doesn't. Every time, he'll say it's the other guys fault. Sometimes his software even fails unsafe and he still blames everybody else.

The '0day' username bug in systemd exemplifies this. Lennart decided that usernames beginning with numbers weren't valid, even though Linux permits it. Systemd was found to run service files with User=0day specified as root instead, not as the user 0day. To Lennart this was not a bug because in his subjective opinion the rest of the system was in error for permitting a username beginning with a number. Even if he were right that usernames beginning with numbers shouldn't be valid, the mere fact that they can occur is reason enough to code defensively around it. At the very least systemd could fail safe when it encounters such an 'invalid' username. But no, he thought there was nothing wrong with failing-to-root. It was everybody else's fault, of course.

https://lwn.net/Articles/727490/

https://github.com/systemd/systemd/issues/6237#issuecomment-...