From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935355Ab0CMBRL (ORCPT ); Fri, 12 Mar 2010 20:17:11 -0500 Received: from kroah.org ([198.145.64.141]:60969 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934965Ab0CMAUq (ORCPT ); Fri, 12 Mar 2010 19:20:46 -0500 X-Mailbox-Line: From gregkh@kvm.kroah.org Fri Mar 12 16:15:12 2010 Message-Id: <20100313001512.683183873@kvm.kroah.org> User-Agent: quilt/0.48-4.4 Date: Fri, 12 Mar 2010 16:13:04 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Henrique de Moraes Holschuh Subject: [patch 086/123] thinkpad-acpi: lock down video output state access In-Reply-To: <20100313001618.GA9811@kroah.com> In-Reply-To: <20100313001618.GA9811@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.33-stable review patch. If anyone has any objections, please let me know. ----------------- From: Henrique de Moraes Holschuh commit b525c06cdbd8a3963f0173ccd23f9147d4c384b5 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- Documentation/laptops/thinkpad-acpi.txt | 4 ++++ drivers/platform/x86/Kconfig | 10 ++++++++-- drivers/platform/x86/thinkpad_acpi.c | 15 +++++++++++++-- 3 files changed, 25 insertions(+), 4 deletions(-) --- a/Documentation/laptops/thinkpad-acpi.txt +++ b/Documentation/laptops/thinkpad-acpi.txt @@ -650,6 +650,10 @@ LCD, CRT or DVI (if available). The foll 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. --- a/drivers/platform/x86/Kconfig +++ b/drivers/platform/x86/Kconfig @@ -319,9 +319,15 @@ config THINKPAD_ACPI_VIDEO server running, phase of the moon, and the current mood of Schroedinger's cat. If you can use X.org's RandR to control your ThinkPad's video output ports instead of this feature, - don't think twice: do it and say N here to save some memory. + don't think twice: do it and say N here to save memory and avoid + bad interactions with X.org. - If you are not sure, say Y here. + NOTE: access to this feature is limited to processes with the + CAP_SYS_ADMIN capability, to avoid local DoS issues in platforms + where it interacts badly with X.org. + + If you are not sure, say Y here but do try to check if you could + be using X.org RandR instead. config THINKPAD_ACPI_HOTKEY_POLL bool "Support NVRAM polling for hot keys" --- a/drivers/platform/x86/thinkpad_acpi.c +++ b/drivers/platform/x86/thinkpad_acpi.c @@ -286,6 +286,7 @@ struct ibm_init_struct { char param[32]; int (*init) (struct ibm_init_struct *); + mode_t base_procfs_mode; struct ibm_struct *data; }; @@ -4629,6 +4630,10 @@ static int video_read(struct seq_file *m return 0; } + /* Even reads can crash X.org, so... */ + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + status = video_outputsw_get(); if (status < 0) return status; @@ -4662,6 +4667,10 @@ static int video_write(char *buf) if (video_supported == TPACPI_VIDEO_NONE) return -ENODEV; + /* Even reads can crash X.org, let alone writes... */ + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + enable = 0; disable = 0; @@ -8506,9 +8515,10 @@ static int __init ibm_init(struct ibm_in "%s installed\n", ibm->name); if (ibm->read) { - mode_t mode; + mode_t mode = iibm->base_procfs_mode; - mode = S_IRUGO; + if (!mode) + mode = S_IRUGO; if (ibm->write) mode |= S_IWUSR; entry = proc_create_data(ibm->name, mode, proc_dir, @@ -8699,6 +8709,7 @@ static struct ibm_init_struct ibms_init[ #ifdef CONFIG_THINKPAD_ACPI_VIDEO { .init = video_init, + .base_procfs_mode = S_IRUSR, .data = &video_driver_data, }, #endif