kernel/sysctl.c: add cap_last_cap to /proc/sys/kernel Userspace needs to know the highest valid capability of the running kernel, which right now cannot reliably be retrieved from the header files only. The fact that this value cannot be determined properly right now creates various problems for libraries compiled on newer header files which are run on older kernels. They assume capabilities are available which actually aren’t. libcap-ng is one example. And we ran into the same problem with systemd too.
Now the capability is exported in /proc/sys/kernel/cap_last_cap.