/usr/share/common-lisp/source/slime/swank/ is in cl-swank 2:2.10.1-3.
This file is owned by root:root, with mode 0o755.
..
/usr/share/common-lisp/source/slime/swank/abcl.lisp
/usr/share/common-lisp/source/slime/swank/allegro.lisp
/usr/share/common-lisp/source/slime/swank/backend.lisp
/usr/share/common-lisp/source/slime/swank/ccl.lisp
/usr/share/common-lisp/source/slime/swank/clisp.lisp
/usr/share/common-lisp/source/slime/swank/cmucl.lisp
/usr/share/common-lisp/source/slime/swank/corman.lisp
/usr/share/common-lisp/source/slime/swank/ecl.lisp
/usr/share/common-lisp/source/slime/swank/gray.lisp
/usr/share/common-lisp/source/slime/swank/lispworks.lisp
/usr/share/common-lisp/source/slime/swank/match.lisp
/usr/share/common-lisp/source/slime/swank/mkcl.lisp
/usr/share/common-lisp/source/slime/swank/rpc.lisp
/usr/share/common-lisp/source/slime/swank/sbcl.lisp
/usr/share/common-lisp/source/slime/swank/scl.lisp
/usr/share/common-lisp/source/slime/swank/source-file-cache.lisp
/usr/share/common-lisp/source/slime/swank/source-path-parser.lisp