Re: [PATCH] tpm: remove chip_num parameter from in-kernel API

[PrasannaKumar Muralidharan <prasannatsmkumar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 24 October 2017 at 21:14, Jarkko Sakkinen
<jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> wrote:
> On Mon, Oct 23, 2017 at 10:31:39AM -0600, Jason Gunthorpe wrote:
>> On Mon, Oct 23, 2017 at 10:07:31AM -0400, Stefan Berger wrote:
>>
>> > >-int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
>> > >+int tpm_pcr_extend(int pcr_idx, const u8 *hash)
>> > >  {
>> >
>> >
>> > I think every kernel internal TPM driver API should be called with the
>> > tpm_chip as a parameter. This is in foresight of namespacing of IMA where we
>> > want to provide the flexibility of passing a dedicated vTPM to each
>> > namespace and IMA would use the chip as a parameter to all of these
>> > functions to talk to the right tpm_vtpm_proxy instance. From that
>> > perspective this patch goes into the wrong direction.
>>
>> Yes, we should ultimately try and get to there.. Someday the
>> tpm_chip_find_get() will need to become namespace aware.
>>
>> But this patch is along the right path, eliminating the chip_num is
>> the right thing to do..
>>
>> > >-  tpm2 = tpm_is_tpm2(TPM_ANY_NUM);
>> > >+  tpm2 = tpm_is_tpm2();
>> > >   if (tpm2 < 0)
>> > >           return tpm2;
>> > >
>> > >@@ -1008,7 +1007,7 @@ static int trusted_instantiate(struct key *key,
>> > >   switch (key_cmd) {
>> > >   case Opt_load:
>> > >           if (tpm2)
>> > >-                  ret = tpm_unseal_trusted(TPM_ANY_NUM, payload, options);
>> > >+                  ret = tpm_unseal_trusted(payload, options);
>>
>> Sequences like this are sketchy.
>>
>> It should be
>>
>> struct tpm_chip *tpm;
>>
>> tpm = tpm_chip_find_get()
>> tpm2 = tpm_is_tpm2(tpm);
>>
>> [..]
>>
>> if (tpm2)
>>      ret = tpm_unseal_trusted(tpm, payload, options);
>>
>> [..]
>>
>> tpm_put_chip(tpm);
>>
>> As hot plug could alter the 'tpm' between the two tpm calls.
>>
>> Jason
>
> This patch just removes bunch of dead code. It does not change existing
> semantics. What you are saying should be done after the dead code has
> been removed. This commit is first step to that direction.
>
> /Jarkko

Please check the RFC [1]. It does use chip id. The rfc has issues and
has to be fixed but still there could be users of the API.

1. https://www.spinics.net/lists/linux-crypto/msg28282.html

Regards,
PrasannaKumar

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