linux-kernel - Re: [PATCH v5 2/7] tpm: remove definition of TPM2_ACTIVE_PCR

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Message-ID: <4a55ba02-87e6-9258-038e-e4c57f00f033@huawei.com>
Date:   Thu, 29 Nov 2018 13:04:40 +0100
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
CC:     <zohar@...ux.ibm.com>, <david.safford@...com>,
        <monty.wiseman@...com>, <linux-integrity@...r.kernel.org>,
        <linux-security-module@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <silviu.vlasceanu@...wei.com>
Subject: Re: [PATCH v5 2/7] tpm: remove definition of TPM2_ACTIVE_PCR_BANKS

On 11/28/2018 1:17 PM, Roberto Sassu wrote:
> On 11/16/2018 2:38 PM, Jarkko Sakkinen wrote:
>> On Wed, Nov 14, 2018 at 04:31:03PM +0100, Roberto Sassu wrote:
>>> tcg_efi_specid_event and tcg_pcr_event2 declaration contains static 
>>> arrays
>>> for a list of hash algorithms used for event logs and event log digests.
>>>
>>> However, according to TCG EFI Protocol Specification, these arrays have
>>> variable sizes. Setting the array size to zero or 3 does not make any
>>> difference, because the parser has to adjust the offset depending on the
>>> actual array size to access structure members after the static arrays.
>>>
>>> Thus, this patch removes the declaration of TPM2_ACTIVE_PCR_BANKS and 
>>> sets
>>> the array size to zero.
>>>
>>> Fixes: 4d23cc323cdb ("tpm: add securityfs support for TPM 2.0 firmware
>>> event log")
>>>
>>> Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
>>> ---
>>>   include/linux/tpm_eventlog.h | 5 ++---
>>>   1 file changed, 2 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/include/linux/tpm_eventlog.h b/include/linux/tpm_eventlog.h
>>> index 20d9da77fc11..3d5d162f09cc 100644
>>> --- a/include/linux/tpm_eventlog.h
>>> +++ b/include/linux/tpm_eventlog.h
>>> @@ -8,7 +8,6 @@
>>>   #define TCG_EVENT_NAME_LEN_MAX    255
>>>   #define MAX_TEXT_EVENT        1000    /* Max event string length */
>>>   #define ACPI_TCPA_SIG        "TCPA"    /* 0x41504354 /'TCPA' */
>>> -#define TPM2_ACTIVE_PCR_BANKS    3
>>>   #define EFI_TCG2_EVENT_LOG_FORMAT_TCG_1_2 0x1
>>>   #define EFI_TCG2_EVENT_LOG_FORMAT_TCG_2   0x2
>>> @@ -90,7 +89,7 @@ struct tcg_efi_specid_event {
>>>       u8 spec_errata;
>>>       u8 uintnsize;
>>>       u32 num_algs;
>>> -    struct tcg_efi_specid_event_algs 
>>> digest_sizes[TPM2_ACTIVE_PCR_BANKS];
>>> +    struct tcg_efi_specid_event_algs digest_sizes[0];
>>>       u8 vendor_info_size;
>>>       u8 vendor_info[0];
>>>   } __packed;
>>> @@ -117,7 +116,7 @@ struct tcg_pcr_event2 {
>>>       u32 pcr_idx;
>>>       u32 event_type;
>>>       u32 count;
>>> -    struct tpm2_digest digests[TPM2_ACTIVE_PCR_BANKS];
>>> +    struct tpm2_digest digests[0];
>>>       struct tcg_event_field event;
>>>   } __packed;
>>> -- 
>>> 2.17.1
>>>
>>
>> NAK for the same reason as last time.
> 
> I added this comment to include/linux/tpm_eventlog.h:
> 
> /*
>   * http://www.trustedcomputinggroup.org/tcg-efi-protocol-specification/
>   *
>   * Set the size of 'digest_sizes' and 'digests', members of 
> tcg_efi_specid_event
>   * and tcg_pcr_event2, to zero. Structures with variable-sized arrays 
> placed
>   * midway are not suitable for type casting.
>   */
> 

If this comment is ok, I will send a new version of the patch set.

Roberto


>> /Jarkko
>>
> 

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