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

[Jason Gunthorpe <jgunthorpe@obsidianresearch.com>]

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