linux-kernel - Re: [PATCH v5 1/2] acpi: Extend TPM2 ACPI table with missing log fields

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Message-ID: <bbd532a8-c745-00e6-b002-5d092f630ed6@linux.ibm.com>
Date:   Thu, 25 Jun 2020 08:10:32 -0400
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc:     Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Jiandi An <anjiandi@...eaurora.org>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-security-module@...r.kernel.org,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH v5 1/2] acpi: Extend TPM2 ACPI table with missing log
 fields

On 6/24/20 10:34 PM, Jarkko Sakkinen wrote:
> On Wed, Jun 24, 2020 at 08:38:25PM -0400, Stefan Berger wrote:
>> On 6/24/20 8:00 PM, Jarkko Sakkinen wrote:
>>> On Tue, Jun 23, 2020 at 08:06:35AM -0400, Stefan Berger wrote:
>>>> From: Stefan Berger <stefanb@...ux.ibm.com>
>>>>
>>>> Recent extensions of the TPM2 ACPI table added 3 more fields
>>>> including 12 bytes of start method specific parameters and Log Area
>>>> Minimum Length (u32) and Log Area Start Address (u64). So, we extend
>>>> the existing structure with these fields to allow non-UEFI systems
>>>> to access the TPM2's log.
>>>>
>>>> The specification that has the new fields is the following:
>>>>     TCG ACPI Specification
>>>>     Family "1.2" and "2.0"
>>>>     Version 1.2, Revision 8
>>>>
>>>> Adapt all existing table size calculations to use
>>>> offsetof(struct acpi_table_tpm2, start_method_specific)
>>>> [where start_method_specific is a newly added field]
>>>> rather than sizeof(struct acpi_table_tpm2) so that the addition
>>>> of the new fields does not affect current systems that may not
>>>> have them.
>>>>
>>> I found at least one regression from this patch. Please remove my
>>> reviewed-by comment form the next version.
>>>
>>> Should have:
>>>
>>>     Link: https://trustedcomputinggroup.org/wp-content/uploads/TCG_ACPIGeneralSpecification_v1.20_r8.pdf
>>>
>>> Please, add this.
>>>
>>>> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>
>>>> Cc: linux-acpi@...r.kernel.org
>>>> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>>>> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
>>>> ---
>>>>    drivers/char/tpm/tpm_crb.c | 13 ++++++++++---
>>>>    drivers/char/tpm/tpm_tis.c |  4 +++-
>>>>    include/acpi/actbl3.h      |  5 +++--
>>>>    3 files changed, 16 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
>>>> index a9dcf31eadd2..0565aa5482f9 100644
>>>> --- a/drivers/char/tpm/tpm_crb.c
>>>> +++ b/drivers/char/tpm/tpm_crb.c
>>>> @@ -669,7 +669,9 @@ static int crb_acpi_add(struct acpi_device *device)
>>>>    	status = acpi_get_table(ACPI_SIG_TPM2, 1,
>>>>    				(struct acpi_table_header **) &buf);
>>>> -	if (ACPI_FAILURE(status) || buf->header.length < sizeof(*buf)) {
>>>> +	if (ACPI_FAILURE(status) || buf->header.length <
>>>> +			offsetof(struct acpi_table_tpm2,
>>>> +				 start_method_specific)) {
>>>>    		dev_err(dev, FW_BUG "failed to get TPM2 ACPI table\n");
>>>>    		return -EINVAL;
>>>>    	}
>>>> @@ -684,14 +686,19 @@ static int crb_acpi_add(struct acpi_device *device)
>>>>    		return -ENOMEM;
>>>>    	if (sm == ACPI_TPM2_COMMAND_BUFFER_WITH_ARM_SMC) {
>>>> -		if (buf->header.length < (sizeof(*buf) + sizeof(*crb_smc))) {
>>>> +		if (buf->header.length <
>>>> +			(offsetof(struct acpi_table_tpm2,
>>>> +				  start_method_specific) +
>>> Should be
>>>
>>>     offsetof(struct acpti_table_tpm2, log_area_minimum_length)
>>
>> The old code had sizeof(*buf) with buf being 'struct acpi_table_tpm2' and
>> that was equivalent to offsetof(struct acpi_table_tpm2,
>> start_method_specific) since 'start_method_specific' is the first new field
>> that we are adding right here. Also see 3rd paragraph in the patch
>> description. The replacement rule described there should apply to all
>> sizeof() calculations on 'struct acpi_table_tpm2.'
> Aren't you ignoring sizeof(*crb_smc) then?

It's still there.