/usr/ is in ruby-buff-ruby-engine 1.0.0-0ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/
/usr/lib/ruby/
/usr/lib/ruby/vendor_ruby/
/usr/lib/ruby/vendor_ruby/buff/
/usr/lib/ruby/vendor_ruby/buff/ruby_engine/
/usr/lib/ruby/vendor_ruby/buff/ruby_engine/kernel_ext.rb
/usr/lib/ruby/vendor_ruby/buff/ruby_engine/version.rb
/usr/lib/ruby/vendor_ruby/buff/ruby_engine.rb
/usr/lib/ruby/vendor_ruby/buff-ruby_engine.rb
/usr/share/
/usr/share/doc/
/usr/share/doc/ruby-buff-ruby-engine/
/usr/share/doc/ruby-buff-ruby-engine/README.md
/usr/share/doc/ruby-buff-ruby-engine/changelog.Debian.gz
/usr/share/doc/ruby-buff-ruby-engine/copyright
/usr/share/rubygems-integration/
/usr/share/rubygems-integration/all/
/usr/share/rubygems-integration/all/specifications/
/usr/share/rubygems-integration/all/specifications/buff-ruby_engine-1.0.0.gemspec