Comment by viraptor
3 years ago
You're right. I didn't see SYS... symbols being actually used, but they are: https://git.tukaani.org/?p=xz.git;a=blob;f=src/xz/sandbox.c;...
This doesn't change my opinion in general - that version should be exposed through a library call and knowing about the specific syscalls shouldn't be needed in xv.
I see your point, but suggesting adding an additional library dependency while we're discussing a supply chain attack is quite ironic.
Should've said function call not library call. My bad. Basically if you already have the linux/landlock.h, that should provide everything you need to do without explicit references to SYS...
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.
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