/usr/share/texmf/doc/fonts/cm-super is in cm-super-minimal 0.3.4-4ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/texmf/doc/fonts/../../../doc/cm-super-minimal
/usr/share/texmf/doc/fonts/../../../doc/cm-super-minimal