Re: [PATCH URGENT FIX] security: keys: trusted: fix lost handle flush

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

On Fri, 2019-12-13 at 11:10 +0530, Sumit Garg wrote:
> On Thu, 12 Dec 2019 at 23:28, James Bottomley
> <James.Bottomley@hansenpartnership.com> wrote:
> > 
> > The original code, before it was moved into security/keys/trusted-
> > keys had a flush after the blob unseal.  Without that flush, the
> > volatile handles increase in the TPM until it becomes unusable and
> > the system either has to be rebooted or the TPM volatile area
> > manually flushed. Fix by adding back the lost flush, which we now
> > have to export because of the relocation of the trusted key code
> > may cause the consumer to be modular.
> > 
> > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.c
> > om>
> > Fixes: 2e19e10131a0 ("KEYS: trusted: Move TPM2 trusted keys code")
> > 
> 
> Overall looks good to me with following minor comment.
> 
> > ---
> >  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..13696deceae8 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_GPL(tpm2_flush_context);
> > 
> >  struct tpm2_get_cap_out {
> >         u8 more_data;
> > diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> > index 0d6e949ba315..03e9b184411b 100644
> > --- a/include/linux/tpm.h
> > +++ b/include/linux/tpm.h
> > @@ -403,6 +403,7 @@ extern int tpm_pcr_extend(struct tpm_chip
> > *chip, u32 pcr_idx,
> >  extern int tpm_send(struct tpm_chip *chip, void *cmd, size_t
> > buflen);
> >  extern int tpm_get_random(struct tpm_chip *chip, u8 *data, size_t
> > max);
> >  extern struct tpm_chip *tpm_default_chip(void);
> > +void tpm2_flush_context(struct tpm_chip *chip, u32 handle);
> 
> Shouldn't this be declared as "extern" similar to other APIs?

extern has no meaning for function declarations and our coding guide
does say do not use it but I think it's advisory not mandatory so I've
no objection to changing it if we prefer consistency over the style
guide.

>  Also, I think we need "#else" part for this API as well.

No, we shouldn't ... the #else part is only for functions which are
called when the TPM isn't compiled in.  That should never happen with
tpm2_flush_context, so if it ever does we want the compile to break.

James