linux-kernel - Re: [PATCH v3 1/5] tpm: change the end marker of the active

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Date:   Thu, 01 Nov 2018 10:42:57 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>,
        jarkko.sakkinen@...ux.intel.com
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, silviu.vlasceanu@...wei.com
Subject: Re: [PATCH v3 1/5] tpm: change the end marker of the active_banks
 array to zero

On Wed, 2018-10-31 at 10:43 -0400, Mimi Zohar wrote:
> On Tue, 2018-10-30 at 16:47 +0100, Roberto Sassu wrote:
> > This patch changes the end marker of the active_banks array from
> > TPM2_ALG_ERROR to zero.
> 
> The patch description is a bit off.
> 
> TPM2_ALG_ERROR is defined as zero.  Since tpm_chip_alloc() calls
> kzalloc to allocate the structure, there is no need to explicitly set
> the active_banks end marker to TPM2_ALG_ERROR, nor is there a need to
> explicitly test for the end marker.
> 
> This patch removes explicitly setting the end marker and changes the
> coding style.
> 
> > 
> > Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> > ---
> >  drivers/char/tpm/tpm-interface.c | 2 +-
> >  drivers/char/tpm/tpm2-cmd.c      | 3 ---
> >  2 files changed, 1 insertion(+), 4 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> > index 1a803b0cf980..f7fc4b5ee239 100644
> > --- a/drivers/char/tpm/tpm-interface.c
> > +++ b/drivers/char/tpm/tpm-interface.c
> > @@ -1051,7 +1051,7 @@ int tpm_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash)
> >  		memset(digest_list, 0, sizeof(digest_list));
> >  
> >  		for (i = 0; i < ARRAY_SIZE(chip->active_banks) &&
> > -			    chip->active_banks[i] != TPM2_ALG_ERROR; i++) {
> > +			    chip->active_banks[i]; i++) {
> >  			digest_list[i].alg_id = chip->active_banks[i];
> >  			memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
> >  			count++;

The fourth patch further updates this code.  Please move those changes
to this first patch.  No need to touch the same code in both places.

                for (i = 0; i < ARRAY_SIZE(chip->active_banks) &&
-                           chip->active_banks[i]; i++) {
-                       digest_list[i].alg_id = chip->active_banks[i];
+                           chip->active_banks[i].alg_id; i++) {
+                       digest_list[i].alg_id = chip->active_banks[i].alg_id;
                        memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
                        count++;
                }
Mimi

> > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> > index c31b490bd41d..046c9d8f3c1e 100644
> > --- a/drivers/char/tpm/tpm2-cmd.c
> > +++ b/drivers/char/tpm/tpm2-cmd.c
> > @@ -908,9 +908,6 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
> >  	}
> >  
> >  out:
> > -	if (i < ARRAY_SIZE(chip->active_banks))
> > -		chip->active_banks[i] = TPM2_ALG_ERROR;
> > -
> >  	tpm_buf_destroy(&buf);
> >  
> >  	return rc;
>