Since Linux 6.9, LUKS suspend stopped wiping disk-encryption keys from memory

So. For the past few days I've been deep in a fun and very rewarding, but also extremely scary debugging saga. To cut a long git-bisecting story short: Since Linux 6.9 (May 2024), the tool that locks the laptop's drive on suspend had been silently failing. Like many of my friends, I use full-disk encryption (LUKS) to protect my data if my laptop is lost, seized or stolen. Highly recommended to everyone; in combination with tested and automated backups, it contributes greatly to peace o