RE: [PATCH] tpm: fix incorrect success returns from tpm_try_transmit()

["Winkler, Tomas" <tomas.winkler@intel.com>]

> 
> On Mon, Dec 31, 2018 at 10:27:31AM -0800, James Bottomley wrote:
> > Ever since 627448e85c766 "tpm: separate cmd_ready/go_idle from
> > runtime_pm" we have been returning success from tpm_try_transmit()
> > even if an error occurred.  The reason is that the introduction of rc
> > = tpm_go_idle() at the end of processing overwrites the value of rc if
> > it contains an error code (mostly with success).  Fix this by writing
> > the return to a new variable rc1 instead.
> >
> > Fixes: 627448e85c766 "tpm: separate cmd_ready/go_idle from runtime_pm"
> > Cc: stable@vger.kernel.org
> > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> >
> > ---
> >
> > Note: the goto out looks fishy as well.  The only go_idle implementor
> > is tpm_crb and that can return a timeout as -ETIME, so it looks like
> > it would then loop forever
> >
> > diff --git a/drivers/char/tpm/tpm-interface.c
> > b/drivers/char/tpm/tpm-interface.c
> > index 129f640424b7..ac7ebab6140c 100644
> > --- a/drivers/char/tpm/tpm-interface.c
> > +++ b/drivers/char/tpm/tpm-interface.c
> > @@ -432,7 +432,7 @@ static ssize_t tpm_try_transmit(struct tpm_chip
> *chip,
> >  				unsigned int flags)
> >  {
> >  	struct tpm_output_header *header = (void *)buf;
> > -	int rc;
> > +	int rc, rc1;
> >  	ssize_t len = 0;
> >  	u32 count, ordinal;
> >  	unsigned long stop;
> > @@ -547,8 +547,8 @@ static ssize_t tpm_try_transmit(struct tpm_chip
> *chip,
> >  		dev_err(&chip->dev, "tpm2_commit_space: error %d\n", rc);
> >
> >  out:
> > -	rc = tpm_go_idle(chip, flags);
> > -	if (rc)
> > +	rc1 = tpm_go_idle(chip, flags);
> > +	if (rc1)
> >  		goto out;
> >
> >  	if (need_locality)
> 
> Thanks James and sorry for latency (holiday season). Just a small suggestion. I
> would just:
> 
> if (tpm_go_idle(chip, flags))
> 	goto out;
> 
> What do you think?


This is wrong as well because of the jump to 'out'.
I've introduced this bug in version 4 of the patch, when the wrappers were added, before the jump to 'out' was correct.
If it's okay with you I will post my version of the fix.
Thanks
Tomas