xfree86: set a sane umask before opening the log

Xorg creates its log file following the umask of the user running
startx, which may result in a world-writable log.  Set umask to 022 to
prevent this.

Debian bug#555308 <http://bugs.debian.org/555308>
See also http://thread.gmane.org/gmane.comp.security.oss.general/2299

Signed-off-by: Julien Cristau <jcristau@debian.org>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

hw/xfree86/common/xf86Init.c

@@ -1151,8 +1151,10 @@ OsVendorInit(void)
   signal(SIGCHLD, SIG_DFL);	/* Need to wait for child processes */
 #endif
 
-  if (!beenHere)
+  if (!beenHere) {
+    umask(022);
     xf86LogInit();
+  }
 
         /* Set stderr to non-blocking. */
 #ifndef O_NONBLOCK