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

[Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>]

On Thu, Jan 03, 2019 at 01:37:09PM +0000, Winkler, Tomas wrote:
> > 
> > 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

Works for me.

/Jarkko