* ext/socket/unixsocket.c (rsock_init_unixsock): check NUL bytes.
  https://hackerone.com/reports/302997

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@62973 b2dd03c8-39d4-4d8f-98ff-823fe69b080e