[raimue]

Now we are running in circles. As you see in the git commit, the compile check was added because the existance of linux/landlock.h alone was not enough to check that the feature can be used.

This header defines the data types for the Linux kernel interface, but not how the syscall landlock_create_ruleset(2) will be issued. That is provided by libc either as a separate wrapper function (does not exist in glibc) or the implementation needs to use syscall(SYS_landlock_create_ruleset, ...), with the constant also being provided by libc. That is how it works for all syscalls and you won't be able to change this.

[SAI_Peregrinus]

The only source of the claim that the existence of.linux/landlock.h is insufficient is (AFAICT) the malicious git commit. Why trust the comment, written by the attacker, to explain away a malicious change?

[raimue]

I already explained above why the existence of linux/landlock.h is not sufficient. Why do you still question it? If you know a bit about system programming and how configure checks work, the change in itself is totally reasonable.