From b525c06cdbd8a3963f0173ccd23f9147d4c384b5 Mon Sep 17 00:00:00 2001 From: Henrique de Moraes Holschuh Date: Thu, 25 Feb 2010 22:22:22 -0300 Subject: thinkpad-acpi: lock down video output state access Given the right combination of ThinkPad and X.org, just reading the video output control state is enough to hard-crash X.org. Until the day I somehow find out a model or BIOS cut date to not provide this feature to ThinkPads that can do video switching through X RandR, change permissions so that only processes with CAP_SYS_ADMIN can access any sort of video output control state. This bug could be considered a local DoS I suppose, as it allows any non-privledged local user to cause some versions of X.org to hard-crash some ThinkPads. Reported-by: Jidanni Signed-off-by: Henrique de Moraes Holschuh Cc: stable@kernel.org --- Documentation/laptops/thinkpad-acpi.txt | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'Documentation') diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt index 75afa1229fd..39c0a09d010 100644 --- a/Documentation/laptops/thinkpad-acpi.txt +++ b/Documentation/laptops/thinkpad-acpi.txt @@ -650,6 +650,10 @@ LCD, CRT or DVI (if available). The following commands are available: echo expand_toggle > /proc/acpi/ibm/video echo video_switch > /proc/acpi/ibm/video +NOTE: Access to this feature is restricted to processes owning the +CAP_SYS_ADMIN capability for safety reasons, as it can interact badly +enough with some versions of X.org to crash it. + Each video output device can be enabled or disabled individually. Reading /proc/acpi/ibm/video shows the status of each device. -- cgit v1.2.3-18-g5258