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

Thu Jan 27 17:08:32 UTC 2011

On 01/25/2011 02:37 AM, Stefan Bader wrote:
> 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
>
>

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

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