tuned-gui: fixed pkexec to work from GNOME Shell

GNOME Shell doesn't seem to run applications through the shell or with some
persistent parent, thus pkexec cannot be execed over the original tuned-gui
process, because it wouldn't pass the pkexec getppid check. The check is
there to ensure that the pkexec will not be owned by the init process.

This fix runs the pkexec as a child process. The minor drawback is that
there will be two tuned-gui processes - the original process running under
the user and the pkexeced process running under the root. The original
process will effectively do nothing, it will just wait for the pkexeced
process to exit.

Resolves: rhbz#1377896

Signed-off-by: Jaroslav Škarvada <[email protected]>

tuned-gui.desktop

@@ -3,7 +3,7 @@ Encoding=UTF-8
 Name=tuned-gui
 GenericName=tuned-gui
 Comment=GTK GUI that can control Tuned daemon and provides simple profile editor
-Exec=pkexec /usr/sbin/tuned-gui
+Exec=tuned-gui
 Icon=tuned
 Terminal=false
 Type=Application

tuned-gui.py

@@ -49,6 +49,7 @@
 import time
 import configobj
 
+import subprocess
 import tuned.logs
 import tuned.consts as consts
 import tuned.version as version
@@ -1017,9 +1018,14 @@ def _start_tuned(self):
 
 	if os.geteuid() != 0:
 		try:
-			os.execvp('pkexec', ['pkexec ' + EXECNAME, EXECNAME] + sys.argv[1:])
-		except (IOError, OSError) as e:
-			pass
+			# Explicitly disabling shell to be safe
+			ec = subprocess.call(['pkexec', EXECNAME] + sys.argv[1:], shell = False)
+		except (subprocess.CalledProcessError) as e:
+			print >> sys.stderr, 'Error elevating privileges: %s' % e
+		else:
+			# If not pkexec error
+			if ec not in [126, 127]:
+				sys.exit(0)
 		# In case of error elevating privileges
 		print >> sys.stderr, 'Superuser permissions are required to run the daemon.'
 		sys.exit(1)