bug#32413: 25.2; When run as root, emacs writes dconf files in a non-root user's /run/user/XXX directory

[Vincent Lefevre]

Original bug report:

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=891063

In summary:

Just after one logs in, does a "su" and runs Emacs, Emacs writes
dconf files in a non-root user's /run/user/XXX directory (related
to DBUS_SESSION_BUS_ADDRESS or XDG_RUNTIME_DIR). I got:

zira:~> ll /run/user/1000
total 0
srw-rw-rw- 1 vinc17 vinc17   0 2018-02-22 04:02:21 bus=
drwx------ 3 vinc17 vinc17  60 2018-02-22 04:02:21 dbus-1/
drwx------ 2 root   root    60 2018-02-22 04:02:32 dconf/
             ^^^^^^^^^^^
drwx------ 2 vinc17 vinc17 140 2018-02-22 04:02:21 gnupg/
drwx------ 2 vinc17 vinc17  40 2018-02-22 04:03:28 gvfs/
drwx------ 2 vinc17 vinc17  80 2018-02-22 04:02:21 pulse/
drwxr-xr-x 2 vinc17 vinc17  80 2018-02-22 04:02:21 systemd/

Unsurprisingly, this then yields issues when one runs Emacs
as a normal user:

(emacs:8958): dconf-CRITICAL **: unable to create file 
'/run/user/1000/dconf/user': Permission denied.  dconf will not work properly.
[...]

Emacs should never create files/directories if the user hasn't
explicitly asked it to do that, in particular if this is under
a directory owned by a different user.



In GNU Emacs 25.2.2 (x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2018-07-11, modified by Debian built on x86-ubc-01
Windowing system distributor 'The X.Org Foundation', version 11.0.12000000
System Description:     Debian GNU/Linux stable-updates (sid)

Configured using:
 'configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs25:/etc/emacs:/usr/local/share/emacs/25.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/25.2/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --build x86_64-linux-gnu
 --prefix=/usr --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs25:/etc/emacs:/usr/local/share/emacs/25.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/25.2/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-x=yes --with-x-toolkit=gtk3
 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
 -fdebug-prefix-map=/build/emacs25-cfFROJ/emacs25-25.2+1=.
 -fstack-protector-strong -Wformat -Werror=format-security -Wall'
 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GSETTINGS NOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11

Important settings:
  value of $LC_COLLATE: POSIX
  value of $LC_CTYPE: en_US.UTF-8
  value of $LC_TIME: en_DK
  value of $LANG: POSIX
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  display-time-mode: t
  show-paren-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
Loading /etc/emacs/site-start.d/50latex-cjk-common.el (source)...done
Loading /etc/emacs/site-start.d/50latex-cjk-thai.el (source)...done
Loading /etc/emacs/site-start.d/50psvn.el (source)...done
Loading /etc/emacs/site-start.d/50python-docutils.el (source)...done
Loading /etc/emacs/site-start.d/50rnc-mode.el (source)...done
Loading /etc/emacs/site-start.d/50texlive-lang-english.el (source)...done
Loading /etc/emacs/site-start.d/50why3.el (source)...done
Loading /home/vinc17/share/emacs/site-lisp/mutteditor.el (source)...done
Loading time...done
For information about GNU Emacs and the GNU system, type C-h C-a.

Load-path shadows:
/usr/share/emacs/25.2/site-lisp/why3 hides /usr/share/emacs/site-lisp/why3
/usr/share/emacs/25.2/site-lisp/debian-startup hides 
/usr/share/emacs/site-lisp/debian-startup
/usr/share/emacs25/site-lisp/cmake-data/cmake-mode hides 
/usr/share/emacs/site-lisp/cmake-mode
/usr/share/emacs/site-lisp/rst hides /usr/share/emacs/25.2/lisp/textmodes/rst
/usr/share/emacs25/site-lisp/latex-cjk-thai/thai-word hides 
/usr/share/emacs/25.2/lisp/language/thai-word

Features:
(shadow sort mail-extr warnings emacsbug message dired format-spec
rfc822 mml mml-sec password-cache epg epg-config gnus-util mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums mm-util help-fns help-mode easymenu
mail-prsvr mail-utils time cus-start cus-load paren cc-styles cc-align
cc-engine cc-vars cc-defs edmacro kmacro cl-loaddefs pcase cl-lib
time-date mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel x-win term/common-win x-dnd tool-bar dnd fontset
image regexp-opt fringe tabulated-list newcomment elisp-mode lisp-mode
prog-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cl-generic cham
georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese charscript case-table epa-hook
jka-cmpr-hook help simple abbrev minibuffer cl-preloaded nadvice
loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote dbusbind inotify dynamic-setting
system-font-setting font-render-setting move-toolbar gtk x-toolkit x
multi-tty make-network-process emacs)

Memory information:
((conses 16 107170 5004)
 (symbols 48 22452 0)
 (miscs 40 55 113)
 (strings 32 20688 4143)
 (string-bytes 1 602044)
 (vectors 16 12882)
 (vector-slots 8 443217 3065)
 (floats 8 171 101)
 (intervals 56 267 0)
 (buffers 976 18))