Re: [v8,09/10] tpm: Initialize TPM and get durations and timeouts

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

On Sun, Mar 13, 2016 at 06:54:39PM -0400, Stefan Berger wrote:
> Add the retrieval of TPM 1.2 durations and timeouts. Since this requires
> the startup of the TPM, do this for TPM 1.2 and TPM 2.
> 
> Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
> CC: linux-kernel@vger.kernel.org
> CC: linux-doc@vger.kernel.org
> CC: linux-api@vger.kernel.org
> 
> ---
> drivers/char/tpm/tpm_vtpm_proxy.c | 95 +++++++++++++++++++++++++++++++++++----
>  1 file changed, 86 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
> index 2bb2c8c..7fd686b 100644
> --- a/drivers/char/tpm/tpm_vtpm_proxy.c
> +++ b/drivers/char/tpm/tpm_vtpm_proxy.c
> @@ -45,8 +45,11 @@ struct proxy_dev {
>  	size_t req_len;              /* length of queued TPM request */
>  	size_t resp_len;             /* length of queued TPM response */
>  	u8 buffer[TPM_BUFSIZE];      /* request/response buffer */
> +
> +	struct work_struct work;     /* task that retrieves TPM timeouts */
>  };
>  
> +static struct workqueue_struct *workqueue;
>  
>  static void vtpm_proxy_delete_device(struct proxy_dev *proxy_dev);
>  
> @@ -67,6 +70,15 @@ static ssize_t vtpm_proxy_fops_read(struct file *filp, char __user *buf,
>  	size_t len;
>  	int sig, rc;
>  
> +	mutex_lock(&proxy_dev->buf_lock);
> +
> +	if (!(proxy_dev->state & STATE_OPENED_FLAG)) {
> +		mutex_unlock(&proxy_dev->buf_lock);
> +		return -EPIPE;
> +	}
> +
> +	mutex_unlock(&proxy_dev->buf_lock);
> +
>  	sig = wait_event_interruptible(proxy_dev->wq, proxy_dev->req_len != 0);
>  	if (sig)
>  		return -EINTR;

What if STATE_OPENED_FLAG is set after mutex_unlock()?

Is there some scenario where STATE_OPENED_FLAG would evaluate false
at this point?

Actually I couldn't find a scenario where this check would be needed
because:

* In vtpm_proxy_work() vtpm_proxy_fops_undo_open() is called after
  sending TPM commands.
* vtpm_proxy_delete_device() calls vtpm_proxy_work_stop() as its
  first statement.

Am I ignoring something?

/Jarkko


> @@ -110,6 +122,11 @@ static ssize_t vtpm_proxy_fops_write(struct file *filp, const char __user *buf,
>  
>  	mutex_lock(&proxy_dev->buf_lock);
>  
> +	if (!(proxy_dev->state & STATE_OPENED_FLAG)) {
> +		mutex_unlock(&proxy_dev->buf_lock);
> +		return -EPIPE;
> +	}
> +
>  	if (count > sizeof(proxy_dev->buffer) ||
>  	    !(proxy_dev->state & STATE_WAIT_RESPONSE_FLAG)) {
>  		mutex_unlock(&proxy_dev->buf_lock);
> @@ -154,6 +171,9 @@ static unsigned int vtpm_proxy_fops_poll(struct file *filp, poll_table *wait)
>  	if (proxy_dev->req_len)
>  		ret |= POLLIN | POLLRDNORM;
>  
> +	if (!(proxy_dev->state & STATE_OPENED_FLAG))
> +		ret |= POLLHUP;
> +
>  	mutex_unlock(&proxy_dev->buf_lock);
>  
>  	return ret;
> @@ -341,6 +361,55 @@ static const struct tpm_class_ops vtpm_proxy_tpm_ops = {
>  };
>  
>  /*
> + * Code related to the startup of the TPM 2 and startup of TPM 1.2 +
> + * retrieval of timeouts and durations.
> + */
> +
> +static void vtpm_proxy_work(struct work_struct *work)
> +{
> +	struct proxy_dev *proxy_dev = container_of(work, struct proxy_dev,
> +						   work);
> +	int rc;
> +
> +	if (proxy_dev->flags & VTPM_PROXY_FLAG_TPM2)
> +		rc = tpm2_startup(proxy_dev->chip, TPM2_SU_CLEAR);
> +	else
> +		rc = tpm_get_timeouts(proxy_dev->chip);
> +
> +	if (rc)
> +		goto err;
> +
> +	rc = tpm_chip_register(proxy_dev->chip);
> +	if (rc)
> +		goto err;
> +
> +	return;
> +
> +err:
> +	vtpm_proxy_fops_undo_open(proxy_dev);
> +}
> +
> +/*
> + * vtpm_proxy_work_stop: make sure the work has finished
> + *
> + * This function is useful when user space closed the fd
> + * while the driver still determines timeouts.
> + */
> +static void vtpm_proxy_work_stop(struct proxy_dev *proxy_dev)
> +{
> +	vtpm_proxy_fops_undo_open(proxy_dev);
> +	flush_work(&proxy_dev->work);
> +}
> +
> +/*
> + * vtpm_proxy_work_start: Schedule the work for TPM 1.2 & 2 initialization
> + */
> +static inline void vtpm_proxy_work_start(struct proxy_dev *proxy_dev)
> +{
> +	queue_work(workqueue, &proxy_dev->work);
> +}
> +
> +/*
>   * Code related to creation and deletion of device pairs
>   */
>  static struct proxy_dev *vtpm_proxy_create_proxy_dev(void)
> @@ -355,6 +424,7 @@ static struct proxy_dev *vtpm_proxy_create_proxy_dev(void)
>  
>  	init_waitqueue_head(&proxy_dev->wq);
>  	mutex_init(&proxy_dev->buf_lock);
> +	INIT_WORK(&proxy_dev->work, vtpm_proxy_work);
>  
>  	chip = tpm_chip_alloc(NULL, &vtpm_proxy_tpm_ops);
>  	if (IS_ERR(chip)) {
> @@ -425,9 +495,7 @@ static struct file *vtpm_proxy_create_device(
>  	if (proxy_dev->flags & VTPM_PROXY_FLAG_TPM2)
>  		proxy_dev->chip->flags |= TPM_CHIP_FLAG_TPM2;
>  
> -	rc = tpm_chip_register(proxy_dev->chip);
> -	if (rc)
> -		goto err_vtpm_fput;
> +	vtpm_proxy_work_start(proxy_dev);
>  
>  	vtpm_new_dev->fd = fd;
>  	vtpm_new_dev->major = MAJOR(proxy_dev->chip->dev.devt);
> @@ -436,12 +504,6 @@ static struct file *vtpm_proxy_create_device(
>  
>  	return file;
>  
> -err_vtpm_fput:
> -	put_unused_fd(fd);
> -	fput(file);
> -
> -	return ERR_PTR(rc);
> -
>  err_put_unused_fd:
>  	put_unused_fd(fd);
>  
> @@ -456,6 +518,8 @@ err_delete_proxy_dev:
>   */
>  static void vtpm_proxy_delete_device(struct proxy_dev *proxy_dev)
>  {
> +	vtpm_proxy_work_stop(proxy_dev);
> +
>  	/*
>  	 * A client may hold the 'ops' lock, so let it know that the server
>  	 * side shuts down before we try to grab the 'ops' lock when
> @@ -555,11 +619,24 @@ static int __init vtpm_module_init(void)
>  		return rc;
>  	}
>  
> +	workqueue = create_workqueue("tpm-vtpm");
> +	if (!workqueue) {
> +		pr_err("couldn't create workqueue\n");
> +		rc = -ENOMEM;
> +		goto err_vtpmx_cleanup;
> +	}
> +
>  	return 0;
> +
> +err_vtpmx_cleanup:
> +	vtpmx_cleanup();
> +
> +	return rc;
>  }
>  
>  static void __exit vtpm_module_exit(void)
>  {
> +	destroy_workqueue(workqueue);
>  	vtpmx_cleanup();
>  }
>