linux-kernel - Re: [PATCH v7 1/5] tpm: dynamically allocate the allocated

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Date:   Sat, 22 Dec 2018 02:03:21 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Roberto Sassu <roberto.sassu@...wei.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 v7 1/5] tpm: dynamically allocate the allocated_banks
 array

On Fri, Dec 21, 2018 at 10:40:09AM +0100, Roberto Sassu wrote:
> On 12/20/2018 3:55 PM, Jarkko Sakkinen wrote:
> > On Thu, Dec 13, 2018 at 11:29:41AM +0100, Roberto Sassu wrote:
> > > This patch renames active_banks (member of tpm_chip) to allocated_banks,
> > > stores the number of allocated PCR banks in nr_allocated_banks (new member
> > > of tpm_chip), and replaces the static array with a pointer to a dynamically
> > > allocated array.
> > > 
> > > tpm2_get_pcr_allocation() determines if a PCR bank is allocated by checking
> > > the mask in the TPML_PCR_SELECTION structure returned by the TPM for
> > > TPM2_Get_Capability(). If a bank is not allocated, the TPM returns that
> > > bank in TPML_PCR_SELECTION, with all bits in the mask set to zero. In this
> > > case, the bank is not included in chip->allocated_banks, to avoid that TPM
> > > driver users unnecessarily calculate a digest for that bank.
> > > 
> > > One PCR bank with algorithm set to SHA1 is always allocated for TPM 1.x.
> > > 
> > > As a consequence of the introduction of nr_allocated_banks,
> > > tpm_pcr_extend() does not check anymore if the algorithm stored in tpm_chip
> > > is equal to zero.
> > > 
> > > Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> > > Tested-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> > > ---
> > >   drivers/char/tpm/tpm-chip.c      |  1 +
> > >   drivers/char/tpm/tpm-interface.c | 18 +++++++++--------
> > >   drivers/char/tpm/tpm.h           |  3 ++-
> > >   drivers/char/tpm/tpm1-cmd.c      | 10 ++++++++++
> > >   drivers/char/tpm/tpm2-cmd.c      | 34 ++++++++++++++++++++++----------
> > >   5 files changed, 47 insertions(+), 19 deletions(-)
> > > 
> > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > > index 32db84683c40..ce851c62bb68 100644
> > > --- a/drivers/char/tpm/tpm-chip.c
> > > +++ b/drivers/char/tpm/tpm-chip.c
> > > @@ -160,6 +160,7 @@ static void tpm_dev_release(struct device *dev)
> > >   	kfree(chip->log.bios_event_log);
> > >   	kfree(chip->work_space.context_buf);
> > >   	kfree(chip->work_space.session_buf);
> > > +	kfree(chip->allocated_banks);
> > >   	kfree(chip);
> > >   }
> > > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> > > index d9439f9abe78..7b80919228be 100644
> > > --- a/drivers/char/tpm/tpm-interface.c
> > > +++ b/drivers/char/tpm/tpm-interface.c
> > > @@ -488,8 +488,7 @@ EXPORT_SYMBOL_GPL(tpm_pcr_read);
> > >   int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash)
> > >   {
> > >   	int rc;
> > > -	struct tpm2_digest digest_list[ARRAY_SIZE(chip->active_banks)];
> > > -	u32 count = 0;
> > > +	struct tpm2_digest *digest_list;
> > >   	int i;
> > >   	chip = tpm_find_get_ops(chip);
> > > @@ -497,16 +496,19 @@ int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash)
> > >   		return -ENODEV;
> > >   	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> > > -		memset(digest_list, 0, sizeof(digest_list));
> > > +		digest_list = kcalloc(chip->nr_allocated_banks,
> > > +				      sizeof(*digest_list), GFP_KERNEL);
> > > +		if (!digest_list)
> > > +			return -ENOMEM;
> > 
> > You could preallocate digest list and place it to struct tpm_chip
> > instead of doing it everytime tpm_pcr_extend() called.
> 
> This part will be removed with patch 5/5.

Even if it did, it does not make this patch unbroken.

/Jarkko