From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Roberto Sassu <roberto.sassu@huawei.com>
Cc: tpmdd-devel@lists.sourceforge.net,
linux-ima-devel@lists.sourceforge.net,
linux-security-module@vger.kernel.org, keyrings@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/5] tpm: introduce tpm_pcr_algorithms()
Date: Wed, 24 May 2017 10:35:21 -0700 [thread overview]
Message-ID: <20170524173521.yiiohct7brkcozyk@intel.com> (raw)
In-Reply-To: <cc7efaa2-4d5b-2142-3b23-06864589c212@huawei.com>
On Mon, May 22, 2017 at 11:07:54AM +0200, Roberto Sassu wrote:
> On 5/20/2017 3:18 PM, Jarkko Sakkinen wrote:
> > On Wed, May 17, 2017 at 10:42:35AM +0200, Roberto Sassu wrote:
> > > On 5/15/2017 3:18 PM, Roberto Sassu wrote:
> > > >
> > > >
> > > > On 5/15/2017 12:36 PM, Jarkko Sakkinen wrote:
> > > > > On Fri, May 05, 2017 at 04:21:48PM +0200, Roberto Sassu wrote:
> > > > > > This function allows TPM users to know which algorithms the TPM
> > > > > > supports.
> > > > > > It stores the algorithms in a static array of 'enum tpm2_algorithms',
> > > > > > allocated by the caller. If the array is not large enough, the function
> > > > > > returns an error. Otherwise, it returns the number of algorithms written
> > > > > > to the array. If the TPM version is 1.2, the function writes
> > > > > > TPM2_ALG_SHA1
> > > > > > to first element of the array.
> > > > > >
> > > > > > Writing the algorithm also for TPM 1.2 has the advantage that callers
> > > > > > can use the API, tpm_pcr_algorithms() and tpm_pcr_extend(), regardless
> > > > > > of the TPM version.
> > > > > >
> > > > > > A minor change added to this patch was to make available the size of
> > > > > > the active_banks array, member of the tpm_chip structure, outside
> > > > > > the TPM driver. The array size (TPM_ACTIVE_BANKS_MAX) has been exported
> > > > > > to include/linux/tpm.h.
> > > > > >
> > > > > > With this information, callers of tpm_pcr_algorithms() can provide
> > > > > > a static array with enough room for all the algorithms, instead
> > > > > > of receiving the pointer of a dynamic array that they have to free
> > > > > > later.
> > > > > >
> > > > > > Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> > > > > > ---
> > > > > > v2
> > > > > >
> > > > > > - tpm_pcr_algorithms() returns supported algorithms also for TPM 1.2
> > > > > >
> > > > > > drivers/char/tpm/tpm-interface.c | 46
> > > > > > ++++++++++++++++++++++++++++++++++++++++
> > > > > > drivers/char/tpm/tpm.h | 13 +-----------
> > > > > > include/linux/tpm.h | 19 +++++++++++++++++
> > > > > > 3 files changed, 66 insertions(+), 12 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/char/tpm/tpm-interface.c
> > > > > > b/drivers/char/tpm/tpm-interface.c
> > > > > > index 4ed08ab..b90de3d 100644
> > > > > > --- a/drivers/char/tpm/tpm-interface.c
> > > > > > +++ b/drivers/char/tpm/tpm-interface.c
> > > > > > @@ -911,6 +911,52 @@ int tpm_pcr_extend(u32 chip_num, int pcr_idx,
> > > > > > const u8 *hash)
> > > > > > EXPORT_SYMBOL_GPL(tpm_pcr_extend);
> > > > > >
> > > > > > /**
> > > > > > + * tpm_pcr_algorithms - get TPM IDs of active PCR banks algorithms
> > > > >
> > > > > The grammar is incorrect here I believe. Should rather be
> > > > >
> > > > > "algorithms of the active PCR banks"
> > > > >
> > > > > And there is no such thing as "TPM ID".
> > > > >
> > > > > > + * @chip_num: tpm idx # or ANY
> > > > > > + * @count: # of items in algorithms
> > > > > > + * @algorithms: array of TPM IDs
> > > > > > + *
> > > > > > + * Returns < 0 on error, and the number of active PCR banks on success.
> > > > > > + *
> > > > > > + * TPM 1.2 has always one SHA1 bank.
> > > > > > + */
> > > > > > +int tpm_pcr_algorithms(u32 chip_num, int count,
> > > > > > + enum tpm2_algorithms *algorithms)
> > > > > unsigned int
> > > > >
> > > > > In addition the function name is not too greatg,
> > > > >
> > > > > Your syntax for return value is not correct. In addition after
> > > > > describing the return value there should not be anything. You should
> > > > > study
> > > > >
> > > > > https://www.kernel.org/doc/Documentation/kernel-doc-nano-HOWTO.txt
> > > > >
> > > > > Better name for the function would be tpm_get_pcr_algorithms().
> > > > >
> > > > > > +{
> > > > > > + struct tpm_chip *chip;
> > > > > > + int i;
> > > > > > +
> > > > > > + if (count <= 0 || algorithms == NULL)
> > > > > > + return -EINVAL;
> > > > >
> > > > > Is there a legal case where caller would pass these values? Now it
> > > > > looks like that there is.
> > > > >
> > > > > 'count' should unsigned int and zero should be a legal value for
> > > > > count.
> > > >
> > > > I wanted to avoid that a negative value returned by tpm_pcr_algorithms()
> > > > is passed to tpm_pcr_extend() as unsigned int.
> > > >
> > > >
> > > > > That said I think the whole design is wrong as you could calculate
> > > > > array for algs only one time and pass a const reference to it on
> > > > > request.
> > > >
> > > > Ok. If I understood it correctly, you are saying to pass a const
> > > > reference of chip->active_banks. Then, I should also:
> > >
> > > This is not a viable option. chip could be freed and the reference
> > > becomes invalid, without increasing the reference count.
> > >
> > > Did you think about something different?
> > >
> > > Thanks
> > >
> > > Roberto
> >
> > Two alternatives come in mind.
> >
> > 1. add tpm_put to linclude/linux/tpm.h
> > 2. take put_ops away from the implementation
> > 3. add documentation that tpm_put needs to be called
> >
> > or acceptable alternative would memcpy in the implementation
> >
> > In any case, you should probably drop completely 'count' and have
> > function for getting the number of active banks.
>
> Having a variable number, makes things more complicated.
> In the IMA patch set for multiple template digests,
> the array of algorithms is stored inside a structure
> called digest descriptor. The array size must be fixed,
> to avoid VLAIS (which is not supported by clang).
What is VLAI?
You can always allocate it from heap.
> Since the size of tpm_chip->active_banks is a small number,
> we can drop count, and assume that the size of the array
> passed to tpm_pcr_algorithms() always matches the size
> of the active_banks array.
>
> Roberto
I don't understand what you mean.
/Jarkko
next prev parent reply other threads:[~2017-05-24 17:35 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-05 14:21 [PATCH v2 0/5] Updated API for TPM 2.0 PCR extend Roberto Sassu
2017-05-05 14:21 ` [PATCH v2 1/5] tpm: introduce tpm_pcr_algorithms() Roberto Sassu
2017-05-15 10:36 ` Jarkko Sakkinen
[not found] ` <20170515103623.sumyo2vyldezual2-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-15 13:18 ` Roberto Sassu
[not found] ` <d2974dd2-e30d-e8f0-a60a-2147f3290670-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-17 8:42 ` Roberto Sassu
2017-05-20 13:18 ` Jarkko Sakkinen
[not found] ` <20170520131846.e3niqiknlrttbdf4-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-22 9:07 ` Roberto Sassu
2017-05-24 17:35 ` Jarkko Sakkinen [this message]
[not found] ` <20170524173521.yiiohct7brkcozyk-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-30 8:44 ` Roberto Sassu
[not found] ` <1cf4fbb1-5683-ceb4-2d5b-8ade25a91e83-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-31 11:39 ` Jarkko Sakkinen
2017-05-20 13:00 ` Jarkko Sakkinen
2017-05-05 14:21 ` [PATCH v2 2/5] tpm: introduce tpm_pcr_algo_to_crypto() and tpm_pcr_algo_from_crypto() Roberto Sassu
[not found] ` <20170505142152.29795-3-roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-15 11:16 ` Jarkko Sakkinen
[not found] ` <20170515111629.urjvbhqzohv4vakc-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-15 14:22 ` Roberto Sassu
2017-05-20 13:22 ` Jarkko Sakkinen
[not found] ` <20170520132217.t7n7l2pjn7i63hbm-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-05-22 7:21 ` Roberto Sassu
2017-05-24 17:33 ` Jarkko Sakkinen
2017-05-24 20:25 ` Jarkko Sakkinen
2017-05-30 10:24 ` Roberto Sassu
2017-05-31 11:40 ` Jarkko Sakkinen
2017-05-05 14:21 ` [PATCH v2 3/5] tpm: pass multiple digests to tpm_pcr_extend() Roberto Sassu
[not found] ` <20170505142152.29795-4-roberto.sassu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2017-05-30 3:29 ` [Linux-ima-devel] " Mimi Zohar
2017-05-30 7:28 ` Roberto Sassu
2017-05-30 11:25 ` Mimi Zohar
[not found] ` <1496143547.3841.517.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-05-30 13:25 ` Roberto Sassu
2017-05-05 14:21 ` [PATCH v2 4/5] keys, trusted: modify arguments of tpm_pcr_extend() Roberto Sassu
2017-05-30 3:35 ` [Linux-ima-devel] " Mimi Zohar
[not found] ` <1496115337.3841.485.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-05-30 7:36 ` Roberto Sassu
2017-05-30 12:06 ` Mimi Zohar
[not found] ` <1496145961.3841.537.camel-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
2017-05-30 13:41 ` Roberto Sassu
2017-05-05 14:21 ` [PATCH v2 5/5] ima: " Roberto Sassu
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