drivers/platform/x86/thinkpad_acpi.c in the Linux kernel before 2.6.34 on ThinkPad devices, when the X.Org X server is used, does not properly restrict access to the video output control state, which allows local users to cause a denial of service (system hang) via a (1) read or (2) write operation.
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=565790
http://openwall.com/lists/oss-security/2010/06/23/2
http://openwall.com/lists/oss-security/2010/09/28/1
http://openwall.com/lists/oss-security/2010/09/29/7
http://openwall.com/lists/oss-security/2010/09/30/1
http://openwall.com/lists/oss-security/2010/09/30/6
http://www.debian.org/security/2010/dsa-2126
http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.34