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Date:   Thu, 8 Nov 2018 21:05:23 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     Roberto Sassu <roberto.sassu@huawei.com>
Cc:     zohar@linux.ibm.com, linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        linux-kernel@vger.kernel.org, silviu.vlasceanu@huawei.com
Subject: Re: [PATCH v4 2/6] tpm: remove definition of TPM2_ACTIVE_PCR_BANKS
Message-ID: <20181108190523.GE20608@linux.intel.com>
References: <20181106150159.1136-1-roberto.sassu@huawei.com>
 <20181106150159.1136-3-roberto.sassu@huawei.com>
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On Tue, Nov 06, 2018 at 04:01:55PM +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 and are not suitable for parsing events with type casting.
> 
> Since declaring static arrays with hard-coded sizes does not help to parse
> data after these arrays, this patch removes the declaration of
> TPM2_ACTIVE_PCR_BANKS and sets the size of the arrays above to zero.
> 
> Fixes: 4d23cc323cdb ("tpm: add securityfs support for TPM 2.0 firmware
> event log")
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> 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
> 

I somehow lost your response but what you must do is to explain why is
it OK for last two fields to overlap.

/Jarkko