conf: escape runtime strings in generated .conf files

The runparts directory and the dbus pidfile and daemon paths are
embedded in double-quoted values of the generated block files.  A
literal quote in either ends the value early and libconfuse rejects
the whole file, and a backslash is read as an escape sequence,
silently mangling the path.  The legacy one-liners had no quoting, so
neither failure existed before the block conversion.

conf_escape() doubles backslashes and escapes quotes; verified by
round-tripping hostile paths through cfg_parse_buf().

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

plugins/dbus.c

@@ -100,6 +100,7 @@ static void setup(void *arg)
 {
 	char *group = DBUS_DAEMONGROUP;
 	char *user = DBUS_DAEMONUSER;
+	char esccmd[256];
 	char pid[300];
 	char *pidfn;
 	mode_t prev;
@@ -153,7 +154,10 @@ static void setup(void *arg)
 	 */
 	pid[0] = 0;
 	if (pidfn) {
-		snprintf(pid, sizeof(pid), "\tpidfile     = \"%s\"\n", pidfn);
+		char esc[280];
+
+		snprintf(pid, sizeof(pid), "\tpidfile     = \"%s\"\n",
+			 conf_escape(pidfn, esc, sizeof(esc)));
 		free(pidfn);
 	}
 	conf_save_service(SVC_TYPE_SERVICE, "dbus", "dbus.conf",
@@ -163,7 +167,7 @@ static void setup(void *arg)
 			  "\tcgroup system {}\n"
 			  "%s"
 			  "\tcommand     = \"%s " DBUS_ARGS "\"\n",
-			  pid, cmd);
+			  pid, conf_escape(cmd, esccmd, sizeof(esccmd)));
 	free(cmd);
 }