Re: [PATCH v9 14/17] tpm: remove TPM_TRANSMIT_UNLOCKED flag

Jarkko Sakkinen
2018-11-19T12:38:54Z

On Sun, Nov 18, 2018 at 12:51:04PM -0700, Jason Gunthorpe wrote:
> On Sun, Nov 18, 2018 at 02:47:47PM +0200, Jarkko Sakkinen wrote:
> > Added locking as part of tpm_try_get_ops() and tpm_put_ops() as they are
> > anyway used in most of the call sites except in tpmrm_release() where we
> > take the locks manually.
> >
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> > Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
> > ---
> > drivers/char/tpm/tpm-chip.c | 2 ++
> > drivers/char/tpm/tpm-dev-common.c | 4 +---
> > drivers/char/tpm/tpm-interface.c | 8 --------
> > drivers/char/tpm/tpm.h | 8 ++------
> > drivers/char/tpm/tpm2-cmd.c | 13 ++++---------
> > drivers/char/tpm/tpm2-space.c | 15 ++++++---------
> > 6 files changed, 15 insertions(+), 35 deletions(-)
>
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index 32db84683c40..157505b0f755 100644
> > --- a/drivers/char/tpm/tpm-chip.c
> > +++ b/drivers/char/tpm/tpm-chip.c
> > @@ -58,6 +58,7 @@ int tpm_try_get_ops(struct tpm_chip *chip)
> > if (!chip->ops)
> > goto out_lock;
> >
> > + mutex_lock(&chip->tpm_mutex);
> > return 0;
>
> It really isn't appropriate for something called 'get' to be exclusive
> like this.. Call it tpm_try_lock_ops() ?

Would definitely be appropriate to rename it, yes.

> > diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> > index c7dc54930576..582caefcf19b 100644
> > --- a/drivers/char/tpm/tpm-dev-common.c
> > +++ b/drivers/char/tpm/tpm-dev-common.c
> > @@ -33,7 +33,6 @@ static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
> > struct tpm_header *header = (void *)buf;
> > ssize_t ret, len;
> >
> > - mutex_lock(&chip->tpm_mutex);
>
> The now implicit locking should be tested for using lockdep calls in
> all places that assume the lock is held by the caller.

Yes. Most importantly trusted keys and IMA should be tested with lockdep
turned on.

/Jarkko