Re: [PATCH] tpm: only export stand alone version of flush context command

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On Mon, 2020-09-28 at 20:07 +0300, Jarkko Sakkinen wrote:
> On Mon, Sep 28, 2020 at 07:31:18PM +0300, Jarkko Sakkinen wrote:
> > > Well, um, that's precisely what this function originally did when
> > > it was inside drivers/char/tpm.  You told the guy who did the
> > > move into security/keys/trusted-keys to convert everything to use
> > > tpm_send which encapsulates the get/put operation, which is why
> > > we now have the flush bug.  If you really want it done like this,
> > > then I'd recommend moving everything back to drivers/char/tpm so
> > > we don't have to do a global exposure of a load of tpm internal
> > > functions (i.e. move them from drivers/char/tmp.h to
> > > include/linux/tpm.h and do an export on them).
> > 
> > My BuildRoot test image did not include the patch. I was wondering
> > why I did not bump into deadlock with the fix candidate :-/ Forgot
> > export LINUX_OVERRIDE_SRCDIR.
> > 
> > But you are absolutely correct, thanks for recalling. I made a
> > mistake there.
> > 
> > I do disagree though that this should be moved back to
> > drivers/char/tpm, as also TPM 1.x code lives in trusted-keys. It is
> > good to have API for doing sequences TPM commands and keep the core
> > in drivers/char/tpm.

I think tpm2_load_cmd is likely going to have to move back anyway just
because more things than trusted keys need to use it.  I can't really
see any other use for the seal/unseal so they can stay in trusted keys
until someone finds a use for them.

> > If you look at tpm_send() it is in essence just simply locking TPM
> > and and calling tpm_transmit_cmd(). And tpm_transmit_cmd() is
> > already an exported symbol. It only needs to be declared in
> > include/linux/tpm.h.
> > 
> > I'd suggest that I refine my series to call tpm_transmit_cmd() and
> > we have a fairly clean solution where the load sequence is atomic.
> 
> I see that it is perfectly fine to make tpm_transmit_cmd() globally
> callable. It is already used by tpm_vtpm_proxy and does have clear
> semantics.
> 
> The way you use it is just:
> 
> 1. tpm_try_get_ops
> 2. Use tpm_transmit_cmd() N times.
> 3. tpm_put_ops
> 
> If we moved TPM 2.x trusted keys code back to drivers/char/tpm,for
> the sake of consistency the same would have to be done for TPM 1.2
> code. I'd rather fix the regression and be done with it.
> 
> Or if reverted like that, also asym_tpm.c code should also live
> inside the TPM driver directory.
> 
> All this work with tpm_buf and the locking functions makes most sense
> if it gives ability for callers to build their own TPM commands
> 
> I'm right now building test image with v3 of my fixes (this time
> properly included to the kernel image). I also uploaded the
> (untested) patches over here:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git/log/?h=trusted-fix

I think we can do that ... in which case the fix for the tis interrupt
trigger also becomes a get/put ops around the tpm2_get_tpm_pt.

After the transformation is complete, tpm_send() becomes obsolete,
doesn't it, so it can be removed?

James







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