linux-kernel - [PATCH] tpm: fix crash in tpm

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Date:	Thu,  7 Apr 2016 15:56:10 +0300
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Peter Huewe <peterhuewe@....de>
Cc:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	Marcel Selhorst <tpmdd@...horst.net>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	tpmdd-devel@...ts.sourceforge.net (moderated list:TPM DEVICE DRIVER),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] tpm: fix crash in tpm_tis

rmmod crashes the driver because tpm_chip_unregister() already sets ops
to NULL. Release ops in tpm_dev_release() so that tpm2_shutdown() can be
cleanly executed and also because it is symmetrical where they are
allocated (in tpmm_chip_alloc()).

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Fixes: 4d3eac5e156a ("tpm: Provide strong locking for device removal")
---
 drivers/char/tpm/tpm-chip.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index f62c851..5241bc4 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -127,6 +127,11 @@ static void tpm_dev_release(struct device *dev)
 	idr_remove(&dev_nums_idr, chip->dev_num);
 	mutex_unlock(&idr_lock);
 
+	/* Make the driver uncallable. */
+	down_write(&chip->ops_sem);
+	chip->ops = NULL;
+	up_write(&chip->ops_sem);
+
 	kfree(chip);
 }
 
@@ -266,11 +271,6 @@ static void tpm_del_char_device(struct tpm_chip *chip)
 	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);
-	chip->ops = NULL;
-	up_write(&chip->ops_sem);
 }
 
 static int tpm1_chip_register(struct tpm_chip *chip)
-- 
1.9.1