Open files with O_NOFOLLOW. (CVE-2017-16611)
A non-privileged X client can instruct X server running under root to open any file by creating own directory with "fonts.dir", "fonts.alias" or any font file being a symbolic link to any other file in the system. X server will then open it. This can be issue with special files such as /dev/watchdog.
Signed-off-by: Pierre-Yves <pyu@riseup.net>