Fix CVE-2011-4028: File disclosure vulnerability.

use O_NOFOLLOW to open the existing lock file, so symbolic links
aren't followed, thus avoid revealing if it point to an existing
file.

Signed-off-by: Matthieu Herrb <matthieu.herrb@laas.fr>
Reviewed-by: Alan Coopersmith <alan.coopersmith@oracle.com>

os/utils.c

@@ -318,7 +318,7 @@ LockServer(void)
       /*
        * Read the pid from the existing file
        */
-      lfd = open(LockFile, O_RDONLY);
+      lfd = open(LockFile, O_RDONLY|O_NOFOLLOW);
       if (lfd < 0) {
         unlink(tmp);
         FatalError("Can't read lock file %s\n", LockFile);