linux-kernel - [PATCH] tpm: fix: sanitized code paths in tpm_chip

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Message-Id: <1426654201-4761-1-git-send-email-jarkko.sakkinen@linux.intel.com>
Date:	Wed, 18 Mar 2015 06:50:01 +0200
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Peter Huewe <peterhuewe@....de>, Ashley Lai <ashley@...leylai.com>,
	Marcel Selhorst <tpmdd@...horst.net>
Cc:	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	christophe.ricard@...il.com, jason.gunthorpe@...idianresearch.com,
	stefanb@...ux.vnet.ibm.com,
	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Subject: [PATCH] tpm: fix: sanitized code paths in tpm_chip_register()

I started to work with PPI interface so that it would be available
under character device sysfs directory and realized that chip
registeration was still too messy.

In TPM 1.x in some rare scenarios (errors that almost never occur)
wrong order in deinitialization steps was taken in teardown. I
reproduced these scenarios by manually inserting error codes in the
place of the corresponding function calls.

The key problem is that the teardown is messy with two separate code
paths (this was inherited when moving code from tpm-interface.c).

Moved TPM 1.x specific register/unregister functionality to own helper
functions and added single code path for teardown in tpm_chip_register().
Now the code paths have been fixed and it should be easier to review
later on this part of the code.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
---
 drivers/char/tpm/tpm-chip.c | 56 +++++++++++++++++++++++++++++----------------
 1 file changed, 36 insertions(+), 20 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index cf43f4b..e5b0481 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -170,6 +170,33 @@ static void tpm_dev_del_device(struct tpm_chip *chip)
 	device_unregister(&chip->dev);
 }
 
+static int tpm1_chip_register(struct tpm_chip *chip)
+{
+	int rc;
+
+	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+		return 0;
+
+	rc = tpm_sysfs_add_device(chip);
+	if (rc)
+		return rc;
+
+	chip->bios_dir = tpm_bios_log_setup(chip->devname);
+
+	return 0;
+}
+
+static void tpm1_chip_unregister(struct tpm_chip *chip)
+{
+	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+		return;
+
+	if (chip->bios_dir)
+		tpm_bios_log_teardown(chip->bios_dir);
+
+	tpm_sysfs_del_device(chip);
+}
+
 /*
  * tpm_chip_register() - create a character device for the TPM chip
  * @chip: TPM chip to use.
@@ -185,22 +212,17 @@ int tpm_chip_register(struct tpm_chip *chip)
 {
 	int rc;
 
-	/* Populate sysfs for TPM1 devices. */
-	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
-		rc = tpm_sysfs_add_device(chip);
-		if (rc)
-			goto del_misc;
-
-		chip->bios_dir = tpm_bios_log_setup(chip->devname);
-	}
+	rc = tpm1_chip_register(chip);
+	if (rc)
+		return rc;
 
 	rc = tpm_add_ppi(chip);
 	if (rc)
-		goto del_sysfs;
+		goto out_err;
 
 	rc = tpm_dev_add_device(chip);
 	if (rc)
-		return rc;
+		goto out_err;
 
 	/* Make the chip available. */
 	spin_lock(&driver_lock);
@@ -210,10 +232,9 @@ int tpm_chip_register(struct tpm_chip *chip)
 	chip->flags |= TPM_CHIP_FLAG_REGISTERED;
 
 	return 0;
-del_sysfs:
-	tpm_sysfs_del_device(chip);
-del_misc:
-	tpm_dev_del_device(chip);
+out_err:
+	tpm_remove_ppi(chip);
+	tpm1_chip_unregister(chip);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(tpm_chip_register);
@@ -238,13 +259,8 @@ void tpm_chip_unregister(struct tpm_chip *chip)
 	spin_unlock(&driver_lock);
 	synchronize_rcu();
 
-	if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
-		if (chip->bios_dir)
-			tpm_bios_log_teardown(chip->bios_dir);
-		tpm_sysfs_del_device(chip);
-	}
-
 	tpm_remove_ppi(chip);
+	tpm1_chip_unregister(chip);
 	tpm_dev_del_device(chip);
 }
 EXPORT_SYMBOL_GPL(tpm_chip_unregister);
-- 
2.1.4

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