linux-kernel - Re: [PATCH v4 1/6] tpm: dynamically allocate active

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Message-ID: <20181113170443.GD4752@linux.intel.com>
Date:   Tue, 13 Nov 2018 19:04:43 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>
Cc:     zohar@...ux.ibm.com, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, silviu.vlasceanu@...wei.com
Subject: Re: [PATCH v4 1/6] tpm: dynamically allocate active_banks array

On Tue, Nov 13, 2018 at 02:34:39PM +0100, Roberto Sassu wrote:
> On 11/8/2018 2:46 PM, Jarkko Sakkinen wrote:
> > Orrayn Tue, Nov 06, 2018 at 04:01:54PM +0100, Roberto Sassu wrote:
> > > This patch removes the hard-coded limit of the active_banks array size.
> > > It stores in the tpm_chip structure the number of active PCR banks,
> > > determined in tpm2_get_pcr_allocation(), and replaces the static array
> > > with a pointer to a dynamically allocated array.
> > > 
> > > As a consequence of the introduction of nr_active_banks, tpm_pcr_extend()
> > > does not check anymore if the algorithm stored in tpm_chip is equal to
> > > zero. The active_banks array always contains valid algorithms.
> > > 
> > > Fixes: 1db15344f874 ("tpm: implement TPM 2.0 capability to get active
> > > PCR banks")
> > > 
> > > Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> > > ---
> > >   drivers/char/tpm/tpm-chip.c      |  1 +
> > >   drivers/char/tpm/tpm-interface.c | 19 ++++++++++++-------
> > >   drivers/char/tpm/tpm.h           |  3 ++-
> > >   drivers/char/tpm/tpm2-cmd.c      | 17 ++++++++---------
> > >   4 files changed, 23 insertions(+), 17 deletions(-)
> > > 
> > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > > index 46caadca916a..2a9e8b744436 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->active_banks);
> > >   	kfree(chip);
> > >   }
> > > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> > > index 1a803b0cf980..ba7ca6b3e664 100644
> > > --- a/drivers/char/tpm/tpm-interface.c
> > > +++ b/drivers/char/tpm/tpm-interface.c
> > > @@ -1039,8 +1039,7 @@ static int tpm1_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash,
> > >   int tpm_pcr_extend(struct tpm_chip *chip, int 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);
> > > @@ -1048,16 +1047,22 @@ int tpm_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash)
> > >   		return -ENODEV;
> > 
> > Should take digest_list as input. Probably callers could re-use the
> > same digest_list array multiple times?
> > 
> > Move struct tpm_chip to include/linux/tpm.h so that the caller can query
> > nr_active_banks and active_banks and can create the digest array by
> > itself. Lets do this right at once now that this is being restructured.
> 
> I have to move also other structures and #define. Wouldn't be better to
> introduce a new function to pass to the caller active_banks and
> nr_active_banks?

Revisited. I think it is fine how it is for now and we reconsider
later. Only thing I want to remark is that use should use kcalloc()
instead of kalloc_array() + memset().

/Jarkko