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

[Jarkko Sakkinen <jarkko.sakkinen@linux.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?

/Jarkko