Re: [PATCH v5 2/7] tpm: remove definition of TPM2_ACTIVE_PCR_BANKS

[Roberto Sassu]

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@xxxxxxxxxx>
> > ---
> >   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.
 */

Is it ok?

Thanks

Roberto


> /Jarkko

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