[PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference

[PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference

[Mario Limonciello]

An upcoming Dell platform is causing a NULL pointer dereference
in dell-wmi-sysman initialization.  Validate that the input from
BIOS matches correct ACPI types and abort module initialization
if it fails.

This leads to a memory leak that needs to be cleaned up properly.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
---
 drivers/platform/x86/dell-wmi-sysman/sysman.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/platform/x86/dell-wmi-sysman/sysman.c b/drivers/platform/x86/dell-wmi-sysman/sysman.c
index dc6dd531c996..38b497991071 100644
--- a/drivers/platform/x86/dell-wmi-sysman/sysman.c
+++ b/drivers/platform/x86/dell-wmi-sysman/sysman.c
@@ -419,13 +419,19 @@ static int init_bios_attributes(int attr_type, const char *guid)
 		return retval;
 	/* need to use specific instance_id and guid combination to get right data */
 	obj = get_wmiobj_pointer(instance_id, guid);
-	if (!obj)
+	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
+		release_attributes_data();
 		return -ENODEV;
+	}
 	elements = obj->package.elements;
 
 	mutex_lock(&wmi_priv.mutex);
 	while (elements) {
 		/* sanity checking */
+		if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
+			pr_debug("incorrect element type\n");
+			goto nextobj;
+		}
 		if (strlen(elements[ATTR_NAME].string.pointer) == 0) {
 			pr_debug("empty attribute found\n");
 			goto nextobj;
-- 
2.25.1

RE: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference

[Limonciello, Mario]

+Divya, +Prasanth, +Perry

> -----Original Message-----
> From: Limonciello, Mario <Mario_Limonciello@Dell.com>
> Sent: Friday, January 29, 2021 11:27
> To: Hans De Goede; Mark Gross
> Cc: LKML; platform-driver-x86@vger.kernel.org; Limonciello, Mario
> Subject: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference
> 
> An upcoming Dell platform is causing a NULL pointer dereference
> in dell-wmi-sysman initialization.  Validate that the input from
> BIOS matches correct ACPI types and abort module initialization
> if it fails.
> 
> This leads to a memory leak that needs to be cleaned up properly.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
> ---
>  drivers/platform/x86/dell-wmi-sysman/sysman.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/dell-wmi-sysman/sysman.c
> b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> index dc6dd531c996..38b497991071 100644
> --- a/drivers/platform/x86/dell-wmi-sysman/sysman.c
> +++ b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> @@ -419,13 +419,19 @@ static int init_bios_attributes(int attr_type, const
> char *guid)
>  		return retval;
>  	/* need to use specific instance_id and guid combination to get right
> data */
>  	obj = get_wmiobj_pointer(instance_id, guid);
> -	if (!obj)
> +	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
> +		release_attributes_data();
>  		return -ENODEV;
> +	}
>  	elements = obj->package.elements;
> 
>  	mutex_lock(&wmi_priv.mutex);
>  	while (elements) {
>  		/* sanity checking */
> +		if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
> +			pr_debug("incorrect element type\n");
> +			goto nextobj;
> +		}
>  		if (strlen(elements[ATTR_NAME].string.pointer) == 0) {
>  			pr_debug("empty attribute found\n");
>  			goto nextobj;
> --
> 2.25.1

RE: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference

[Yuan, Perry]

> -----Original Message-----
> From: Limonciello, Mario <Mario_Limonciello@Dell.com>
> Sent: 2021年1月30日 1:29
> To: Hans De Goede; Mark Gross
> Cc: LKML; platform-driver-x86@vger.kernel.org; Bharathi, Divya; Ksr, Prasanth;
> Yuan, Perry
> Subject: RE: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer
> dereference
> 
> +Divya, +Prasanth, +Perry
> 
> > -----Original Message-----
> > From: Limonciello, Mario <Mario_Limonciello@Dell.com>
> > Sent: Friday, January 29, 2021 11:27
> > To: Hans De Goede; Mark Gross
> > Cc: LKML; platform-driver-x86@vger.kernel.org; Limonciello, Mario
> > Subject: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer
> > dereference
> >
> > An upcoming Dell platform is causing a NULL pointer dereference in
> > dell-wmi-sysman initialization.  Validate that the input from BIOS
> > matches correct ACPI types and abort module initialization if it
> > fails.
> >
> > This leads to a memory leak that needs to be cleaned up properly.
> >
> > Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
> > ---
> >  drivers/platform/x86/dell-wmi-sysman/sysman.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > index dc6dd531c996..38b497991071 100644
> > --- a/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > +++ b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> > @@ -419,13 +419,19 @@ static int init_bios_attributes(int attr_type,
> > const char *guid)
> >  		return retval;
> >  	/* need to use specific instance_id and guid combination to get
> > right data */
> >  	obj = get_wmiobj_pointer(instance_id, guid);
> > -	if (!obj)
> > +	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
> > +		release_attributes_data();
> >  		return -ENODEV;
> > +	}
> >  	elements = obj->package.elements;
> >
> >  	mutex_lock(&wmi_priv.mutex);
> >  	while (elements) {
> >  		/* sanity checking */
> > +		if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
> > +			pr_debug("incorrect element type\n");
> > +			goto nextobj;
> > +		}
> >  		if (strlen(elements[ATTR_NAME].string.pointer) == 0) {
> >  			pr_debug("empty attribute found\n");
> >  			goto nextobj;
> > --
> > 2.25.1

Tested on the Dell laptop system which I found the issue. 
Kernel can boot up with this new fix patch without any panic triggered.

Tested-by: Perry Yuan <perry_yuan@dell.com>

Re: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference

[Hans de Goede]

Hi,

On 1/29/21 6:26 PM, Mario Limonciello wrote:
> An upcoming Dell platform is causing a NULL pointer dereference
> in dell-wmi-sysman initialization.  Validate that the input from
> BIOS matches correct ACPI types and abort module initialization
> if it fails.
> 
> This leads to a memory leak that needs to be cleaned up properly.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
> ---
>  drivers/platform/x86/dell-wmi-sysman/sysman.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/dell-wmi-sysman/sysman.c b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> index dc6dd531c996..38b497991071 100644
> --- a/drivers/platform/x86/dell-wmi-sysman/sysman.c
> +++ b/drivers/platform/x86/dell-wmi-sysman/sysman.c
> @@ -419,13 +419,19 @@ static int init_bios_attributes(int attr_type, const char *guid)
>  		return retval;
>  	/* need to use specific instance_id and guid combination to get right data */
>  	obj = get_wmiobj_pointer(instance_id, guid);
> -	if (!obj)
> +	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
> +		release_attributes_data();

All calls of  init_bios_attributes() have the following error handling:

        ret = init_bios_attributes(INT, DELL_WMI_BIOS_INTEGER_ATTRIBUTE_GUID);
        if (ret) {
                pr_debug("failed to populate integer type attributes\n");
                goto fail_create_group;
        }

	...

fail_create_group:
        release_attributes_data();

So that added release_attributes_data() call is not necessary. If you can respin
this patch Monday with the release_attributes_data(); addition dropped, then
I will try to get this to Linus in time for 5.11 .

Or I can fix this up locally if you agree with dropping the unnecessary
release_attributes_data() call.

Regards,

Hans




>  		return -ENODEV;
> +	}
>  	elements = obj->package.elements;
>  
>  	mutex_lock(&wmi_priv.mutex);
>  	while (elements) {
>  		/* sanity checking */
> +		if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
> +			pr_debug("incorrect element type\n");
> +			goto nextobj;
> +		}
>  		if (strlen(elements[ATTR_NAME].string.pointer) == 0) {
>  			pr_debug("empty attribute found\n");
>  			goto nextobj;
> 

Re: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference

[Hans de Goede]

Hi,

On 1/31/21 3:04 PM, Limonciello, Mario wrote:
> 
> 
>> -----Original Message-----
>> From: Hans de Goede <hdegoede@redhat.com>
>> Sent: Saturday, January 30, 2021 15:44
>> To: Limonciello, Mario; Mark Gross
>> Cc: LKML; platform-driver-x86@vger.kernel.org
>> Subject: Re: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer
>> dereference
>>
>>
>> [EXTERNAL EMAIL]
>>
>> Hi,
>>
>> On 1/29/21 6:26 PM, Mario Limonciello wrote:
>>> An upcoming Dell platform is causing a NULL pointer dereference
>>> in dell-wmi-sysman initialization.  Validate that the input from
>>> BIOS matches correct ACPI types and abort module initialization
>>> if it fails.
>>>
>>> This leads to a memory leak that needs to be cleaned up properly.
>>>
>>> Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
>>> ---
>>>  drivers/platform/x86/dell-wmi-sysman/sysman.c | 8 +++++++-
>>>  1 file changed, 7 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/platform/x86/dell-wmi-sysman/sysman.c
>> b/drivers/platform/x86/dell-wmi-sysman/sysman.c
>>> index dc6dd531c996..38b497991071 100644
>>> --- a/drivers/platform/x86/dell-wmi-sysman/sysman.c
>>> +++ b/drivers/platform/x86/dell-wmi-sysman/sysman.c
>>> @@ -419,13 +419,19 @@ static int init_bios_attributes(int attr_type, const
>> char *guid)
>>>  		return retval;
>>>  	/* need to use specific instance_id and guid combination to get right
>> data */
>>>  	obj = get_wmiobj_pointer(instance_id, guid);
>>> -	if (!obj)
>>> +	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
>>> +		release_attributes_data();
>>
>> All calls of  init_bios_attributes() have the following error handling:
>>
>>         ret = init_bios_attributes(INT, DELL_WMI_BIOS_INTEGER_ATTRIBUTE_GUID);
>>         if (ret) {
>>                 pr_debug("failed to populate integer type attributes\n");
>>                 goto fail_create_group;
>>         }
>>
>> 	...
>>
>> fail_create_group:
>>         release_attributes_data();
>>
>> So that added release_attributes_data() call is not necessary. If you can
>> respin
>> this patch Monday with the release_attributes_data(); addition dropped, then
>> I will try to get this to Linus in time for 5.11 .
>>
>> Or I can fix this up locally if you agree with dropping the unnecessary
>> release_attributes_data() call.
>>
> 
> Yes, please go ahead and drop the unnecessary call locally.

Ok, I've merged this into my review-hans branch and I will push this out
to for-next as soon as a local build has finished. I'll also include
this in my last fixes pull-req for Linus later this week.

While working on this I did notice that the function in question still
has a bunch of further issues. But since this patch fixes a crash and has
been tested I've decided to move forward with it as is (with the duplicate
release_attributes_data() call dropped). The further issues can be fixed
with follow-up patches.

So the other issues which I noticed are:

1. Calling release_attributes_data() in the error-path here:

	obj = get_wmiobj_pointer(instance_id, guid);
	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
		return -ENODEV;
	}

Is not necessary as discussed, but the added obj->type != ACPI_TYPE_PACKAGE
which I assume triggers to fix the reported crash, means that obj is not
NULL in which case we should free it. So this should become:

	obj = get_wmiobj_pointer(instance_id, guid);
	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
		kfree(obj);
		return -ENODEV;
	}

Note that the kfree() will be a no-op when obj == NULL. This means that
with just the current fix merged there is a small memleak on machines
where we hit the error-path. I've decided that we can live with that,
since the alternative is the crash or me pushing something untested.


2. There is a while below this if, which gets a new obj pointer:

	obj = get_wmiobj_pointer(instance_id, guid);
	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
		kfree(obj);
		return -ENODEV;
	}
	elements = obj->package.elements;

	mutex_lock(&wmi_priv.mutex);
	while (elements) {
		...

nextobj:
		kfree(obj);
		instance_id++;
		obj = get_wmiobj_pointer(instance_id, guid);
		elements = obj ? obj->package.elements : NULL;
	}

This is missing a check for the obj->type for the new obj when
going into a second (or higher) iteration of the loop.

This check can be added by moving the original check to inside
the loop like this:

	obj = get_wmiobj_pointer(instance_id, guid);

	mutex_lock(&wmi_priv.mutex);	
	while (obj) {
		if (obj->type != ACPI_TYPE_PACKAGE) {
			err = ENODEV;
			goto err_attr_init;
		}
		elements = obj->package.elements;

		...

nextobj:
		kfree(obj);
		instance_id++;
		obj = get_wmiobj_pointer(instance_id, guid);
	}


3. Functions like populate_enum_data() (and the others) index the
elements array with an index > 0 without checking the package length
and also make assumptions about the types embedded in the package
without checking them.


4. The err_attr_init exit path of init_bios_attributes() calls
release_attributes_data() but that call does not just cleanup
the results of that single init_bios_attributes() call but also
of all previous init_bios_attributes() calls as such it makes more
sense to leave the calling of release_attributes_data() to the caller.

Either way calling it twice once from the err_attr_init exit path
and then again in sysman_init() feels wrong, even though I think it
does no harm.

Regards,

Hans














> 
> Thank you
> 
>> Regards,
>>
>> Hans
>>
>>
>>
>>
>>>  		return -ENODEV;
>>> +	}
>>>  	elements = obj->package.elements;
>>>
>>>  	mutex_lock(&wmi_priv.mutex);
>>>  	while (elements) {
>>>  		/* sanity checking */
>>> +		if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
>>> +			pr_debug("incorrect element type\n");
>>> +			goto nextobj;
>>> +		}
>>>  		if (strlen(elements[ATTR_NAME].string.pointer) == 0) {
>>>  			pr_debug("empty attribute found\n");
>>>  			goto nextobj;
>>>
> 

Re: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference

[Perry Yuan]

On 2021/2/1 4:59, Hans de Goede wrote:
> Hi,
> 
> On 1/31/21 3:04 PM, Limonciello, Mario wrote:
>>
>>
>>> -----Original Message-----
>>> From: Hans de Goede <hdegoede@redhat.com>
>>> Sent: Saturday, January 30, 2021 15:44
>>> To: Limonciello, Mario; Mark Gross
>>> Cc: LKML; platform-driver-x86@vger.kernel.org
>>> Subject: Re: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer
>>> dereference
>>>
>>>
>>> [EXTERNAL EMAIL]
>>>
>>> Hi,
>>>
>>> On 1/29/21 6:26 PM, Mario Limonciello wrote:
>>>> An upcoming Dell platform is causing a NULL pointer dereference
>>>> in dell-wmi-sysman initialization.  Validate that the input from
>>>> BIOS matches correct ACPI types and abort module initialization
>>>> if it fails.
>>>>
>>>> This leads to a memory leak that needs to be cleaned up properly.
>>>>
>>>> Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
>>>> ---
>>>>   drivers/platform/x86/dell-wmi-sysman/sysman.c | 8 +++++++-
>>>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/platform/x86/dell-wmi-sysman/sysman.c
>>> b/drivers/platform/x86/dell-wmi-sysman/sysman.c
>>>> index dc6dd531c996..38b497991071 100644
>>>> --- a/drivers/platform/x86/dell-wmi-sysman/sysman.c
>>>> +++ b/drivers/platform/x86/dell-wmi-sysman/sysman.c
>>>> @@ -419,13 +419,19 @@ static int init_bios_attributes(int attr_type, const
>>> char *guid)
>>>>   		return retval;
>>>>   	/* need to use specific instance_id and guid combination to get right
>>> data */
>>>>   	obj = get_wmiobj_pointer(instance_id, guid);
>>>> -	if (!obj)
>>>> +	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
>>>> +		release_attributes_data();
>>>
>>> All calls of  init_bios_attributes() have the following error handling:
>>>
>>>          ret = init_bios_attributes(INT, DELL_WMI_BIOS_INTEGER_ATTRIBUTE_GUID);
>>>          if (ret) {
>>>                  pr_debug("failed to populate integer type attributes\n");
>>>                  goto fail_create_group;
>>>          }
>>>
>>> 	...
>>>
>>> fail_create_group:
>>>          release_attributes_data();
>>>
>>> So that added release_attributes_data() call is not necessary. If you can
>>> respin
>>> this patch Monday with the release_attributes_data(); addition dropped, then
>>> I will try to get this to Linus in time for 5.11 .
>>>
>>> Or I can fix this up locally if you agree with dropping the unnecessary
>>> release_attributes_data() call.
>>>
>>
>> Yes, please go ahead and drop the unnecessary call locally.
> 
> Ok, I've merged this into my review-hans branch and I will push this out
> to for-next as soon as a local build has finished. I'll also include
> this in my last fixes pull-req for Linus later this week.
> 
> While working on this I did notice that the function in question still
> has a bunch of further issues. But since this patch fixes a crash and has
> been tested I've decided to move forward with it as is (with the duplicate
> release_attributes_data() call dropped). The further issues can be fixed
> with follow-up patches.
> 
> So the other issues which I noticed are:
> 
> 1. Calling release_attributes_data() in the error-path here:
> 
> 	obj = get_wmiobj_pointer(instance_id, guid);
> 	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
> 		return -ENODEV;
> 	}
> 
> Is not necessary as discussed, but the added obj->type != ACPI_TYPE_PACKAGE
> which I assume triggers to fix the reported crash, means that obj is not
> NULL in which case we should free it. So this should become:
> 
> 	obj = get_wmiobj_pointer(instance_id, guid);
> 	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
> 		kfree(obj);
> 		return -ENODEV;
> 	}
> 
> Note that the kfree() will be a no-op when obj == NULL. This means that
> with just the current fix merged there is a small memleak on machines
> where we hit the error-path. I've decided that we can live with that,
> since the alternative is the crash or me pushing something untested.
> 
> 
> 2. There is a while below this if, which gets a new obj pointer:
> 
> 	obj = get_wmiobj_pointer(instance_id, guid);
> 	if (!obj || obj->type != ACPI_TYPE_PACKAGE) {
> 		kfree(obj);
> 		return -ENODEV;
> 	}
> 	elements = obj->package.elements;
> 
> 	mutex_lock(&wmi_priv.mutex);
> 	while (elements) {
> 		...
> 
> nextobj:
> 		kfree(obj);
> 		instance_id++;
> 		obj = get_wmiobj_pointer(instance_id, guid);
> 		elements = obj ? obj->package.elements : NULL;
> 	}
> 
> This is missing a check for the obj->type for the new obj when
> going into a second (or higher) iteration of the loop.
> 
> This check can be added by moving the original check to inside
> the loop like this:
> 
> 	obj = get_wmiobj_pointer(instance_id, guid);
> 
> 	mutex_lock(&wmi_priv.mutex);	
> 	while (obj) {
> 		if (obj->type != ACPI_TYPE_PACKAGE) {
> 			err = ENODEV;
> 			goto err_attr_init;
> 		}
> 		elements = obj->package.elements;
> 
> 		...
> 
> nextobj:
> 		kfree(obj);
> 		instance_id++;
> 		obj = get_wmiobj_pointer(instance_id, guid);
> 	}
> 
> 
> 3. Functions like populate_enum_data() (and the others) index the
> elements array with an index > 0 without checking the package length
> and also make assumptions about the types embedded in the package
> without checking them.
> 
> 
> 4. The err_attr_init exit path of init_bios_attributes() calls
> release_attributes_data() but that call does not just cleanup
> the results of that single init_bios_attributes() call but also
> of all previous init_bios_attributes() calls as such it makes more
> sense to leave the calling of release_attributes_data() to the caller.
> 
> Either way calling it twice once from the err_attr_init exit path
> and then again in sysman_init() feels wrong, even though I think it
> does no harm.
> 
> Regards,
> 
> Hans
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
>>
>> Thank you
>>
>>> Regards,
>>>
>>> Hans
>>>
>>>
>>>
>>>
>>>>   		return -ENODEV;
>>>> +	}
>>>>   	elements = obj->package.elements;
>>>>
>>>>   	mutex_lock(&wmi_priv.mutex);
>>>>   	while (elements) {
>>>>   		/* sanity checking */
>>>> +		if (elements[ATTR_NAME].type != ACPI_TYPE_STRING) {
>>>> +			pr_debug("incorrect element type\n");
>>>> +			goto nextobj;
>>>> +		}
>>>>   		if (strlen(elements[ATTR_NAME].string.pointer) == 0) {
>>>>   			pr_debug("empty attribute found\n");
>>>>   			goto nextobj;
>>>>
>>
> 
Hi Hans.
Could you share your the commit link after you apply this patch to your 
for-next branch?

Thank you!
Perry.

Re: [PATCH] platform/x86: dell-wmi-sysman: fix a NULL pointer dereference

[Hans de Goede]

Hi,

On 2/1/21 3:36 AM, Perry Yuan wrote:

<snip>

> Hi Hans.
> Could you share your the commit link after you apply this patch to your for-next branch?

https://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86.git/commit/?h=for-next&id=64b0efa18f8c3b1baac369b8d74d0fdae02bc4bc

Regards,

Hans