[15326] in bugtraq
xfs + gdm allow DoS of console
daemon@ATHENA.MIT.EDU (Mike Leonhard)
Wed Jun 14 15:46:57 2000
Mime-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"
Message-Id: <00e901bfd51a$335ef3b0$1000000a@theytalk.com>
Date: Tue, 13 Jun 2000 10:31:49 +0100
Reply-To: Mike Leonhard <mike@THEYTALK.COM>
From: Mike Leonhard <mike@THEYTALK.COM>
To: BUGTRAQ@SECURITYFOCUS.COM
Content-Transfer-Encoding: 8bit
RedHat 6.2 further extends the xfs problem with its buggy gdm. gdm apparently ignores the --nodaemon option specified to it in inittab. If the X server fails to load for whatever reason, gdm will immediately reload it. This causes the console to become unusable - caught in a loop with the screen flashing every 2 seconds as the X server tries to load. On a machine with no network login capability the only way out of this situation is to reboot the system by pressing CTRL-ALT-DEL on the keyboard. If gdm would exit when the X server quits, then init would reload it in a safe manner - stopping for 5 min if gdm is reloaded, I believe it is, 10 times in one minute.
RedHat's updated gdm rpm as of last week did not resolve this issue. I wonder if it was a good idea to move the 'fixed' font into xfs. I have had good experiences with xfstt, but I have always had my normal X fonts loaded directly from disk.
Mike_L
mike@theytalk.com
----- Original Message -----
From: "Michal Zalewski" <lcamtuf@TPI.PL>
To: <BUGTRAQ@SECURITYFOCUS.COM>
Sent: Sunday, April 16, 2000 2:31 PM
Subject: xfs
Due to improper input validation (NULL pointer occours on strcpy()), any
user may crash X fontserver under RedHat 6.x, causing effective DoS for
whole X server :)
_______________________________________________________
Michal Zalewski [lcamtuf@tpi.pl] [tp.internet/security]
[http://lcamtuf.na.export.pl] <=--=> bash$ :(){ :|:&};:
=-----=> God is real, unless declared integer. <=-----=
