Re: [PATCH 1/8] security: keys: trusted: flush the key handle after use

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Mon, 2019-12-09 at 08:31 +0000, David Woodhouse wrote:
> On Sat, 2019-12-07 at 21:07 -0800, James Bottomley wrote:
> > The trusted keys code currently loads a blob into the TPM and
> > unseals
> > on the handle.  However, it never flushes the handle meaning that
> > volatile contexts build up until the TPM becomes unusable.  Fix
> > this
> > by flushing the handle after the unseal.
> > 
> > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.c
> > om>
> > ---
> >  drivers/char/tpm/tpm.h                    | 1 -
> >  drivers/char/tpm/tpm2-cmd.c               | 1 +
> >  include/linux/tpm.h                       | 1 +
> >  security/keys/trusted-keys/trusted_tpm2.c | 1 +
> >  4 files changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> > index b9e1547be6b5..5620747da0cf 100644
> > --- a/drivers/char/tpm/tpm.h
> > +++ b/drivers/char/tpm/tpm.h
> > @@ -218,7 +218,6 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32
> > pcr_idx,
> >  int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
> >  		    struct tpm_digest *digests);
> >  int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
> > -void tpm2_flush_context(struct tpm_chip *chip, u32 handle);
> >  ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,
> >  			u32 *value, const char *desc);
> >  
> > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-
> > cmd.c
> > index fdb457704aa7..b87592f4a6c7 100644
> > --- a/drivers/char/tpm/tpm2-cmd.c
> > +++ b/drivers/char/tpm/tpm2-cmd.c
> > @@ -362,6 +362,7 @@ void tpm2_flush_context(struct tpm_chip *chip,
> > u32 handle)
> >  	tpm_transmit_cmd(chip, &buf, 0, "flushing context");
> >  	tpm_buf_destroy(&buf);
> >  }
> > +EXPORT_SYMBOL(tpm2_flush_context);
> 
> 
> Everything else is EXPORT_SYMBOL_GPL(). Why EXPORT_SYMBOL() here?

No reason ... well, except I'm not sure the difference has any utility,
but since I don't really care either way, I'll change all the exports.

James