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[v11,16/20] tpm: Make locality requests return consistent values

Message ID 20240913200517.3085794-17-ross.philipson@oracle.com
State New
Headers show
Series x86: Trenchboot secure dynamic launch Linux kernel support | expand

Commit Message

Ross Philipson Sept. 13, 2024, 8:05 p.m. UTC 
From: "Daniel P. Smith" <dpsmith@apertussolutions.com>

The function tpm_tis_request_locality() is expected to return the locality
value that was requested, or a negative error code upon failure. If it is called
while locality_count of struct tis_data is non-zero, no actual locality request
will be sent. Because the ret variable is initially set to 0, the
locality_count will still get increased, and the function will return 0. For a
caller, this would indicate that locality 0 was successfully requested and not
the state changes just mentioned.

Additionally, the function __tpm_tis_request_locality() provides inconsistent
error codes. It will provide either a failed IO write or a -1 should it have
timed out waiting for locality request to succeed.

This commit changes __tpm_tis_request_locality() to return valid negative error
codes to reflect the reason it fails. It then adjusts the return value check in
tpm_tis_request_locality() to check for a non-negative return value before
incrementing locality_cout. In addition, the initial value of the ret value is
set to a negative error to ensure the check does not pass if
__tpm_tis_request_locality() is not called.

Signed-off-by: Daniel P. Smith <dpsmith@apertussolutions.com>
Signed-off-by: Ross Philipson <ross.philipson@oracle.com>
---
 drivers/char/tpm/tpm_tis_core.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

Comments

Jarkko Sakkinen Nov. 1, 2024, 10:04 a.m. UTC | #1 
On Fri Sep 13, 2024 at 11:05 PM EEST, Ross Philipson wrote:
> From: "Daniel P. Smith" <dpsmith@apertussolutions.com>
>
> The function tpm_tis_request_locality() is expected to return the locality
> value that was requested, or a negative error code upon failure. If it is called
> while locality_count of struct tis_data is non-zero, no actual locality request
> will be sent. Because the ret variable is initially set to 0, the
> locality_count will still get increased, and the function will return 0. For a
> caller, this would indicate that locality 0 was successfully requested and not
> the state changes just mentioned.
>
> Additionally, the function __tpm_tis_request_locality() provides inconsistent
> error codes. It will provide either a failed IO write or a -1 should it have
> timed out waiting for locality request to succeed.
>
> This commit changes __tpm_tis_request_locality() to return valid negative error
> codes to reflect the reason it fails. It then adjusts the return value check in
> tpm_tis_request_locality() to check for a non-negative return value before
> incrementing locality_cout. In addition, the initial value of the ret value is
> set to a negative error to ensure the check does not pass if
> __tpm_tis_request_locality() is not called.
>
> Signed-off-by: Daniel P. Smith <dpsmith@apertussolutions.com>
> Signed-off-by: Ross Philipson <ross.philipson@oracle.com>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 22ebf679ea69..20a8b341be0d 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -210,7 +210,7 @@ static int __tpm_tis_request_locality(struct tpm_chip *chip, int l)
>  again:
>  		timeout = stop - jiffies;
>  		if ((long)timeout <= 0)
> -			return -1;
> +			return -EBUSY;
>  		rc = wait_event_interruptible_timeout(priv->int_queue,
>  						      (check_locality
>  						       (chip, l)),
> @@ -229,18 +229,21 @@ static int __tpm_tis_request_locality(struct tpm_chip *chip, int l)
>  			tpm_msleep(TPM_TIMEOUT);
>  		} while (time_before(jiffies, stop));
>  	}
> -	return -1;
> +	return -EBUSY;
>  }
>  
>  static int tpm_tis_request_locality(struct tpm_chip *chip, int l)
>  {
>  	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> -	int ret = 0;
> +	int ret = -EBUSY;
> +
> +	if (l < 0 || l > TPM_MAX_LOCALITY)
> +		return -EINVAL;
>  
>  	mutex_lock(&priv->locality_count_mutex);
>  	if (priv->locality_count == 0)
>  		ret = __tpm_tis_request_locality(chip, l);
> -	if (!ret)
> +	if (ret >= 0)
>  		priv->locality_count++;
>  	mutex_unlock(&priv->locality_count_mutex);
>  	return ret;

First of all, -1 is as consistent value as a value can be.

Secondly:

	if (tpm_tis_request_locality(chip, 0) != 0)
		return -EBUSY;

What am I missing here?

BR, Jarkko
Jarkko Sakkinen Nov. 2, 2024, 2:26 p.m. UTC | #2 
On Fri Sep 13, 2024 at 11:05 PM EEST, Ross Philipson wrote:
> From: "Daniel P. Smith" <dpsmith@apertussolutions.com>
>
> The function tpm_tis_request_locality() is expected to return the locality
> value that was requested, or a negative error code upon failure. If it is called
> while locality_count of struct tis_data is non-zero, no actual locality request
> will be sent. Because the ret variable is initially set to 0, the
> locality_count will still get increased, and the function will return 0. For a
> caller, this would indicate that locality 0 was successfully requested and not
> the state changes just mentioned.
>
> Additionally, the function __tpm_tis_request_locality() provides inconsistent
> error codes. It will provide either a failed IO write or a -1 should it have
> timed out waiting for locality request to succeed.
>
> This commit changes __tpm_tis_request_locality() to return valid negative error
> codes to reflect the reason it fails. It then adjusts the return value check in
> tpm_tis_request_locality() to check for a non-negative return value before
> incrementing locality_cout. In addition, the initial value of the ret value is
> set to a negative error to ensure the check does not pass if
> __tpm_tis_request_locality() is not called.

Tweaked version attached with cruft removed and story cleared.

BR, Jarkko
diff mbox series

Patch

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 22ebf679ea69..20a8b341be0d 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -210,7 +210,7 @@  static int __tpm_tis_request_locality(struct tpm_chip *chip, int l)
 again:
 		timeout = stop - jiffies;
 		if ((long)timeout <= 0)
-			return -1;
+			return -EBUSY;
 		rc = wait_event_interruptible_timeout(priv->int_queue,
 						      (check_locality
 						       (chip, l)),
@@ -229,18 +229,21 @@  static int __tpm_tis_request_locality(struct tpm_chip *chip, int l)
 			tpm_msleep(TPM_TIMEOUT);
 		} while (time_before(jiffies, stop));
 	}
-	return -1;
+	return -EBUSY;
 }
 
 static int tpm_tis_request_locality(struct tpm_chip *chip, int l)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
-	int ret = 0;
+	int ret = -EBUSY;
+
+	if (l < 0 || l > TPM_MAX_LOCALITY)
+		return -EINVAL;
 
 	mutex_lock(&priv->locality_count_mutex);
 	if (priv->locality_count == 0)
 		ret = __tpm_tis_request_locality(chip, l);
-	if (!ret)
+	if (ret >= 0)
 		priv->locality_count++;
 	mutex_unlock(&priv->locality_count_mutex);
 	return ret;