[PATCH] tpm: fix call order in tpm-chip.c

[PATCH] tpm: fix call order in tpm-chip.c

[Jarkko Sakkinen]

- tpm_dev_add_device(): cdev_add() must be done before uevent is
  propagated in order to avoid races.
- tpm_chip_register(): tpm_dev_add_device() must be done as the
  last step before exposing device to the user space in order to
  avoid races.

In addition clarified description in tpm_chip_register().

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 drivers/char/tpm/tpm-chip.c | 34 ++++++++++++++--------------------
 1 file changed, 14 insertions(+), 20 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 1d278cc..e096e9c 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -140,24 +140,24 @@ static int tpm_dev_add_device(struct tpm_chip *chip)
 {
 	int rc;
 
-	rc = device_add(&chip->dev);
+	rc = cdev_add(&chip->cdev, chip->dev.devt, 1);
 	if (rc) {
 		dev_err(&chip->dev,
-			"unable to device_register() %s, major %d, minor %d, err=%d\n",
+			"unable to cdev_add() %s, major %d, minor %d, err=%d\n",
 			chip->devname, MAJOR(chip->dev.devt),
 			MINOR(chip->dev.devt), rc);
 
+		device_unregister(&chip->dev);
 		return rc;
 	}
 
-	rc = cdev_add(&chip->cdev, chip->dev.devt, 1);
+	rc = device_add(&chip->dev);
 	if (rc) {
 		dev_err(&chip->dev,
-			"unable to cdev_add() %s, major %d, minor %d, err=%d\n",
+			"unable to device_register() %s, major %d, minor %d, err=%d\n",
 			chip->devname, MAJOR(chip->dev.devt),
 			MINOR(chip->dev.devt), rc);
 
-		device_unregister(&chip->dev);
 		return rc;
 	}
 
@@ -174,27 +174,17 @@ static void tpm_dev_del_device(struct tpm_chip *chip)
  * tpm_chip_register() - create a character device for the TPM chip
  * @chip: TPM chip to use.
  *
- * Creates a character device for the TPM chip and adds sysfs interfaces for
- * the device, PPI and TCPA. As the last step this function adds the
- * chip to the list of TPM chips available for use.
+ * Creates a character device for the TPM chip and adds sysfs attributes for
+ * the device. As the last step this function adds the chip to the list of TPM
+ * chips available for in-kernel use.
  *
- * NOTE: This function should be only called after the chip initialization
- * is complete.
- *
- * Called from tpm_<specific>.c probe function only for devices
- * the driver has determined it should claim.  Prior to calling
- * this function the specific probe function has called pci_enable_device
- * upon errant exit from this function specific probe function should call
- * pci_disable_device
+ * This function should be only called after the chip initialization is
+ * complete.
  */
 int tpm_chip_register(struct tpm_chip *chip)
 {
 	int rc;
 
-	rc = tpm_dev_add_device(chip);
-	if (rc)
-		return rc;
-
 	/* Populate sysfs for TPM1 devices. */
 	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
 		rc = tpm_sysfs_add_device(chip);
@@ -208,6 +198,10 @@ int tpm_chip_register(struct tpm_chip *chip)
 		chip->bios_dir = tpm_bios_log_setup(chip->devname);
 	}
 
+	rc = tpm_dev_add_device(chip);
+	if (rc)
+		return rc;
+
 	/* Make the chip available. */
 	spin_lock(&driver_lock);
 	list_add_rcu(&chip->list, &tpm_chip_list);
-- 
2.1.4

Re: [PATCH] tpm: fix call order in tpm-chip.c

[Peter Hüwe]

Am Sonntag, 1. März 2015, 22:55:47 schrieb Jarkko Sakkinen:
> - tpm_dev_add_device(): cdev_add() must be done before uevent is
>   propagated in order to avoid races.
> - tpm_chip_register(): tpm_dev_add_device() must be done as the
>   last step before exposing device to the user space in order to
>   avoid races.
> 
> In addition clarified description in tpm_chip_register().
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Looks good to me.
Staged it and I'll send out the pull request in the next few days.

(have to catch up mails from traveling)

Thanks,
Peter