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From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Alexander Steffen <Alexander.Steffen@infineon.com>
Cc: tpmdd-devel@lists.sourceforge.net, linux-security-module@vger.kernel.org
Subject: Re: [PATCH RESEND 1/3] tpm-chip: Move idr_replace calls to appropriate places
Date: Fri, 25 Aug 2017 20:25:46 +0300	[thread overview]
Message-ID: <20170825172546.f4bl2wh7tgbyjx2n@linux.intel.com> (raw)
In-Reply-To: <20170824083714.10016-2-Alexander.Steffen@infineon.com>

On Thu, Aug 24, 2017 at 10:37:12AM +0200, Alexander Steffen wrote:
> According to the comments, adding/removing the chip from the list should be
> the first/last action in (un)register. But currently it is done in a
> subfunction in the middle of the process. Moving the code from the
> subfunctions to the appropriate places within (un)register ensures that the
> code matches the comments.
> 
> Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
> ---
>  drivers/char/tpm/tpm-chip.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 67ec9d3..a353b7a 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -327,11 +327,6 @@ static int tpm_add_char_device(struct tpm_chip *chip)
>  		}
>  	}
>  
> -	/* Make the chip available. */
> -	mutex_lock(&idr_lock);
> -	idr_replace(&dev_nums_idr, chip, chip->dev_num);
> -	mutex_unlock(&idr_lock);
> -
>  	return rc;
>  }
>  
> @@ -339,11 +334,6 @@ static void tpm_del_char_device(struct tpm_chip *chip)
>  {
>  	cdev_device_del(&chip->cdev, &chip->dev);
>  
> -	/* Make the chip unavailable. */
> -	mutex_lock(&idr_lock);
> -	idr_replace(&dev_nums_idr, NULL, chip->dev_num);
> -	mutex_unlock(&idr_lock);
> -
>  	/* Make the driver uncallable. */
>  	down_write(&chip->ops_sem);
>  	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> @@ -438,6 +428,11 @@ int tpm_chip_register(struct tpm_chip *chip)
>  		return rc;
>  	}
>  
> +	/* Make the chip available. */
> +	mutex_lock(&idr_lock);
> +	idr_replace(&dev_nums_idr, chip, chip->dev_num);
> +	mutex_unlock(&idr_lock);
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(tpm_chip_register);
> @@ -457,6 +452,11 @@ EXPORT_SYMBOL_GPL(tpm_chip_register);
>   */
>  void tpm_chip_unregister(struct tpm_chip *chip)
>  {
> +	/* Make the chip unavailable. */
> +	mutex_lock(&idr_lock);
> +	idr_replace(&dev_nums_idr, NULL, chip->dev_num);
> +	mutex_unlock(&idr_lock);
> +
>  	tpm_del_legacy_sysfs(chip);
>  	tpm_bios_log_teardown(chip);
>  	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> -- 

This is unnecessary and questionable code shuffling in a very critical
places of the driver code where race conditions are easily introduced.

If you don't have a better reason to do this, I'm not going to take
this. I also fail to see the connection to the patch set as whole.

/Jarkko

  reply	other threads:[~2017-08-25 17:25 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-24  8:37 [PATCH RESEND 0/3] Export broken TPMs to user space Alexander Steffen
     [not found] ` <20170824083714.10016-1-Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w@public.gmane.org>
2017-08-24  8:37   ` [PATCH RESEND 1/3] tpm-chip: Move idr_replace calls to appropriate places Alexander Steffen
2017-08-25 17:25     ` Jarkko Sakkinen [this message]
     [not found]       ` <20170825172546.f4bl2wh7tgbyjx2n-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-08-28 17:18         ` Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w
2017-08-24  8:37   ` [PATCH RESEND 2/3] tpm-chip: Return TPM error codes from auto_startup functions Alexander Steffen
     [not found]     ` <20170824083714.10016-3-Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w@public.gmane.org>
2017-08-25 17:06       ` Jarkko Sakkinen
     [not found]         ` <20170825170607.wfnr5y5zres2n42r-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-08-29 12:11           ` Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w
2017-08-24  8:37   ` [PATCH RESEND 3/3] tpm-chip: Export TPM device to user space even when startup failed Alexander Steffen
2017-08-25 17:20     ` Jarkko Sakkinen
     [not found]       ` <20170825172021.lw3ycxqw63ubrcm2-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-08-28 17:15         ` Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w
2017-08-29 12:55           ` Jarkko Sakkinen
2017-08-29 13:17             ` [tpmdd-devel] " Michal Suchánek
     [not found]               ` <20170829151739.315ae581-6hIufAJW0g4CVLCxKZUutA@public.gmane.org>
2017-08-29 13:53                 ` Peter Huewe
2017-08-30 10:26                   ` [tpmdd-devel] " Jarkko Sakkinen
2017-08-30 10:15                 ` Jarkko Sakkinen
2017-08-30 10:20                   ` [tpmdd-devel] " Jarkko Sakkinen
2017-08-30 10:34                     ` Michal Suchánek
2017-08-30 11:07                       ` Jarkko Sakkinen
2017-08-31 16:18                         ` Alexander.Steffen
2017-09-02 10:20                           ` Jarkko Sakkinen
     [not found]                   ` <20170830101510.rlkh2p3zecfsrhgl-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
2017-08-30 10:41                     ` Peter Huewe
2017-08-30 11:10                       ` [tpmdd-devel] " Jarkko Sakkinen
2017-08-31 16:26                         ` Alexander.Steffen
2017-09-02 10:24                           ` Jarkko Sakkinen

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