path: root/Documentation/laptops
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authorHenrique de Moraes Holschuh <hmh@hmh.eng.br>2010-02-25 22:22:22 -0300
committerHenrique de Moraes Holschuh <hmh@hmh.eng.br>2010-02-25 22:22:22 -0300
commitb525c06cdbd8a3963f0173ccd23f9147d4c384b5 (patch)
tree025b22fda39fc7a42061ab25a908abe3ae757d3b /Documentation/laptops
parent08fedfc903c78e380b0baa7b57c52d367794d0a5 (diff)
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 <jidanni@jidanni.org> Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> Cc: stable@kernel.org
Diffstat (limited to 'Documentation/laptops')
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index 75afa1229fd7..39c0a09d0105 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.

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