Karmic SRU: thinkpad-acpi: lock down video output state access, CVE-2010-3448

[Stefan Bader]

On 01/24/2011 08:45 PM, Tim Gardner wrote:
> The following changes since commit 09f654208690b182c9c4691aa47e7b7c87325969:
>   Henrique de Moraes Holschuh (1):
>         thinkpad-acpi: lock down video output state access, CVE-2010-3448
> 
> are available in the git repository at:
> 
>   git://kernel.ubuntu.com/rtg/ubuntu-karmic.git CVE-2010-3448
> 
> 
> From 09f654208690b182c9c4691aa47e7b7c87325969 Mon Sep 17 00:00:00 2001
> From: Henrique de Moraes Holschuh <hmh at hmh.eng.br>
> Date: Mon, 24 Jan 2011 08:11:01 -0700
> Subject: [PATCH] thinkpad-acpi: lock down video output state access, CVE-2010-3448
> 
CVE-2010-3448
> BugLink: http://bugs.launchpad.net/bugs/706999
> 
> Back ported from commit b525c06cdbd8a3963f0173ccd23f9147d4c384b5 upstream
> by Tim Gardner <tim.gardner at canonical.com>. Resolves CVE-2010-3448

I probably would put the backported statement just above your sob in the sob
area and the resolves normally is handled by just putting the cve number at
column 1 (like added above).

> 
> 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 at jidanni.org>
> Signed-off-by: Henrique de Moraes Holschuh <hmh at hmh.eng.br>
> Signed-off-by: Greg Kroah-Hartman <gregkh at suse.de>
[maybe?](cherry-picker|backported from commit <sha1> upstream)
> Signed-off-by: Tim Gardner <tim.gardner at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---
>  Documentation/laptops/thinkpad-acpi.txt |    4 ++++
>  drivers/platform/x86/Kconfig            |   10 ++++++++--
>  drivers/platform/x86/thinkpad_acpi.c    |   18 +++++++++++++++---
>  3 files changed, 27 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
> index e2ddcde..fa12ef8 100644
> --- a/Documentation/laptops/thinkpad-acpi.txt
> +++ b/Documentation/laptops/thinkpad-acpi.txt
> @@ -674,6 +674,10 @@ 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.
>  
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 77c6097..bbe9036 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -290,9 +290,15 @@ 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"
> diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
> index 05e5d56..a83803f 100644
> --- a/drivers/platform/x86/thinkpad_acpi.c
> +++ b/drivers/platform/x86/thinkpad_acpi.c
> @@ -235,6 +235,7 @@ struct ibm_init_struct {
>  	char param[32];
>  
>  	int (*init) (struct ibm_init_struct *);
> +	mode_t base_procfs_mode;
>  	struct ibm_struct *data;
>  };
>  
> @@ -4142,6 +4143,10 @@ static int video_read(char *p)
>  		return len;
>  	}
>  
> +	/* Even reads can crash X.org, so... */
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EPERM;
> +
>  	status = video_outputsw_get();
>  	if (status < 0)
>  		return status;
> @@ -4175,6 +4180,10 @@ 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;
>  
> @@ -7357,9 +7366,11 @@ static int __init ibm_init(struct ibm_init_struct *iibm)
>  		"%s installed\n", ibm->name);
>  
>  	if (ibm->read) {
> -		entry = create_proc_entry(ibm->name,
> -					  S_IFREG | S_IRUGO | S_IWUSR,
> -					  proc_dir);
> +		mode_t mode = iibm->base_procfs_mode;
> +
> +		if (!mode)
> +			mode = S_IRUGO;
> +		entry = create_proc_entry(ibm->name, mode, proc_dir);
>  		if (!entry) {
>  			printk(TPACPI_ERR "unable to create proc entry %s\n",
>  			       ibm->name);
> @@ -7555,6 +7566,7 @@ static struct ibm_init_struct ibms_init[] __initdata = {
>  #ifdef CONFIG_THINKPAD_ACPI_VIDEO
>  	{
>  		.init = video_init,
> +		.base_procfs_mode = S_IRUSR,
>  		.data = &video_driver_data,
>  	},
>  #endif