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

[Brad Figg]

On 01/24/2011 11:47 AM, Tim Gardner wrote:
> The following changes since commit e98c9ee35cead70474b238604a6e9edaf91f7270:
>    Jason Gaston (1):
>          ata_piix: IDE mode SATA patch for Intel ICH10 DeviceID's
>
> are available in the git repository at:
>
>    git://kernel.ubuntu.com/rtg/ubuntu-hardy.git CVE-2010-3448
>
> Tim Gardner (1):
>        thinkpad-acpi: lock down video output state access, CVE-2010-3448
>
>   Documentation/thinkpad-acpi.txt |    4 ++++
>   drivers/misc/thinkpad_acpi.c    |   18 +++++++++++++++---
>   drivers/misc/thinkpad_acpi.h    |    1 +
>   3 files changed, 20 insertions(+), 3 deletions(-)
>
>  From 66921b3a1779614924ab89c98f473523dfbe18fa Mon Sep 17 00:00:00 2001
> From: Tim Gardner<tim.gardner at canonical.com>
> Date: Mon, 24 Jan 2011 10:43:57 -0700
> Subject: [PATCH] thinkpad-acpi: lock down video output state access, CVE-2010-3448
>
> BugLink: http://bugs.launchpad.net/bugs/706999
>
> Backported from 2.6.32.y 1b0d63f15fb79d0cb840f8b701f343548b5640e8.
> I dropped part of the patch that applied to drivers/platform/x86/Kconfig
> since its not relevant for 2.6.24.
>
> 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>
> Signed-off-by: Tim Gardner<tim.gardner at canonical.com>
> ---
>   Documentation/thinkpad-acpi.txt |    4 ++++
>   drivers/misc/thinkpad_acpi.c    |   18 +++++++++++++++---
>   drivers/misc/thinkpad_acpi.h    |    1 +
>   3 files changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/thinkpad-acpi.txt b/Documentation/thinkpad-acpi.txt
> index 10c041c..46ae816 100644
> --- a/Documentation/thinkpad-acpi.txt
> +++ b/Documentation/thinkpad-acpi.txt
> @@ -518,6 +518,10 @@ 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/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
> index cf56647..ac866b9 100644
> --- a/drivers/misc/thinkpad_acpi.c
> +++ b/drivers/misc/thinkpad_acpi.c
> @@ -1986,6 +1986,10 @@ 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;
> @@ -2019,6 +2023,10 @@ static int video_write(char *buf)
>   	if (video_supported == TPACPI_VIDEO_NONE)
>   		return -ENODEV;
>
> +	/* Even reads can crash X.org, so... */
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EPERM;
> +
>   	enable = 0;
>   	disable = 0;
>
> @@ -4574,9 +4582,12 @@ 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(IBM_ERR "unable to create proc entry %s\n",
>   			       ibm->name);
> @@ -4758,6 +4769,7 @@ static struct ibm_init_struct ibms_init[] __initdata = {
>   	},
>   	{
>   		.init = video_init,
> +		.base_procfs_mode = S_IRUSR,
>   		.data =&video_driver_data,
>   	},
>   	{
> diff --git a/drivers/misc/thinkpad_acpi.h b/drivers/misc/thinkpad_acpi.h
> index 8fba2bb..9649256 100644
> --- a/drivers/misc/thinkpad_acpi.h
> +++ b/drivers/misc/thinkpad_acpi.h
> @@ -230,6 +230,7 @@ struct ibm_init_struct {
>   	char param[32];
>
>   	int (*init) (struct ibm_init_struct *);
> +	mode_t base_procfs_mode;
>   	struct ibm_struct *data;
>   };
>

Acked-by: Brad Figg <brad.figg at canonical.com>

-- 
Brad Figg brad.figg at canonical.com http://www.canonical.com