Before Linux 6.5, memfd_secret() was disabled by default and only available if the system administrator turned it on using "secretmem.enable=y" kernel parameter.
[...]
"To prevent potential data leaks of memory regions backed by memfd_secret() from a hybernation image, hybernation is prevented when there are active memfd_secret() users."
alt Hacker News
From the man page: Linux 5.14.
Before Linux 6.5, memfd_secret() was disabled by default and only available if the system administrator turned it on using "secretmem.enable=y" kernel parameter. [...]
"To prevent potential data leaks of memory regions backed by memfd_secret() from a hybernation image, hybernation is prevented when there are active memfd_secret() users."