[PATCH v19 1/5] tpm_tis: Fix expected bit handling

[amirmizi6@gmail.com]

From: Amir Mizinski <amirmizi6@gmail.com>

Currently, the driver polls the TPM_STS.stsValid field until TRUE; then it
reads TPM_STS register again to verify only that TPM_STS.expect field is
FALSE (i.e., it ignores TPM_STS.stsValid).
Since TPM_STS.stsValid represents the TPM_STS.expect validity, a check of
only one of these fields is wrong. Fix this condition so that both fields
are checked in the same TPM_STS register read.

Modify the signature of wait_for_tpm_stat() to tpm_tis_wait_for_stat(),
adding an additional "expected" parameter to its call.
tpm_tis_wait_for_stat() is now polling the TPM_STS with a mask and waits
for the value in "expected". This modification adds the ability to check if
certain TPM_STS bits have been cleared.
For example, use the new parameter to check in status that TPM_STS_VALID
is set and also that TPM_STS_EXPECT is zeroed. This prevents a racy
check.

Suggested-by: Benoit Houyere <benoit.houyere@st.com>
Signed-off-by: Amir Mizinski <amirmizi6@gmail.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 drivers/char/tpm/tpm_tis_core.c | 61 ++++++++++++++++++-----------------------
 1 file changed, 27 insertions(+), 34 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 69579ef..f833f35 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -44,9 +44,9 @@ static bool wait_for_tpm_stat_cond(struct tpm_chip *chip, u8 mask,
 	return false;
 }
 
-static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
-		unsigned long timeout, wait_queue_head_t *queue,
-		bool check_cancel)
+static int tpm_tis_wait_for_stat(struct tpm_chip *chip, u8 mask, u8 expected,
+				 unsigned long timeout,
+				 wait_queue_head_t *queue, bool check_cancel)
 {
 	unsigned long stop;
 	long rc;
@@ -55,7 +55,7 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
 
 	/* check current status */
 	status = chip->ops->status(chip);
-	if ((status & mask) == mask)
+	if ((status & mask) == expected)
 		return 0;
 
 	stop = jiffies + timeout;
@@ -83,7 +83,7 @@ static int wait_for_tpm_stat(struct tpm_chip *chip, u8 mask,
 			usleep_range(TPM_TIMEOUT_USECS_MIN,
 				     TPM_TIMEOUT_USECS_MAX);
 			status = chip->ops->status(chip);
-			if ((status & mask) == mask)
+			if ((status & mask) == expected)
 				return 0;
 		} while (time_before(jiffies, stop));
 	}
@@ -259,10 +259,11 @@ static int recv_data(struct tpm_chip *chip, u8 *buf, size_t count)
 	int size = 0, burstcnt, rc;
 
 	while (size < count) {
-		rc = wait_for_tpm_stat(chip,
-				 TPM_STS_DATA_AVAIL | TPM_STS_VALID,
-				 chip->timeout_c,
-				 &priv->read_queue, true);
+		rc = tpm_tis_wait_for_stat(chip,
+					   TPM_STS_DATA_AVAIL | TPM_STS_VALID,
+					   TPM_STS_DATA_AVAIL | TPM_STS_VALID,
+					   chip->timeout_c, &priv->read_queue,
+					   true);
 		if (rc < 0)
 			return rc;
 		burstcnt = get_burstcount(chip);
@@ -315,8 +316,9 @@ static int tpm_tis_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 		goto out;
 	}
 
-	if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
-				&priv->int_queue, false) < 0) {
+	if (tpm_tis_wait_for_stat(chip, TPM_STS_VALID, TPM_STS_VALID,
+				  chip->timeout_c, &priv->int_queue,
+				  false) < 0) {
 		size = -ETIME;
 		goto out;
 	}
@@ -342,14 +344,14 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
 	int rc, status, burstcnt;
 	size_t count = 0;
-	bool itpm = priv->flags & TPM_TIS_ITPM_WORKAROUND;
 
 	status = tpm_tis_status(chip);
 	if ((status & TPM_STS_COMMAND_READY) == 0) {
 		tpm_tis_ready(chip);
-		if (wait_for_tpm_stat
-		    (chip, TPM_STS_COMMAND_READY, chip->timeout_b,
-		     &priv->int_queue, false) < 0) {
+		if (tpm_tis_wait_for_stat(chip, TPM_STS_COMMAND_READY,
+					  TPM_STS_COMMAND_READY,
+					  chip->timeout_b, &priv->int_queue,
+					  false) < 0) {
 			rc = -ETIME;
 			goto out_err;
 		}
@@ -369,34 +371,24 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 			goto out_err;
 
 		count += burstcnt;
-
-		if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
-					&priv->int_queue, false) < 0) {
+		if (tpm_tis_wait_for_stat(chip, TPM_STS_VALID | TPM_STS_DATA_EXPECT,
+					  TPM_STS_VALID | TPM_STS_DATA_EXPECT, chip->timeout_a,
+					  &priv->int_queue, false) < 0) {
 			rc = -ETIME;
 			goto out_err;
 		}
-		status = tpm_tis_status(chip);
-		if (!itpm && (status & TPM_STS_DATA_EXPECT) == 0) {
-			rc = -EIO;
-			goto out_err;
-		}
 	}
 
 	/* write last byte */
 	rc = tpm_tis_write8(priv, TPM_DATA_FIFO(priv->locality), buf[count]);
 	if (rc < 0)
 		goto out_err;
-
-	if (wait_for_tpm_stat(chip, TPM_STS_VALID, chip->timeout_c,
-				&priv->int_queue, false) < 0) {
+	if (tpm_tis_wait_for_stat(chip, TPM_STS_VALID | TPM_STS_DATA_EXPECT,
+				  TPM_STS_VALID, chip->timeout_a,
+				  &priv->int_queue, false) < 0) {
 		rc = -ETIME;
 		goto out_err;
 	}
-	status = tpm_tis_status(chip);
-	if (!itpm && (status & TPM_STS_DATA_EXPECT) != 0) {
-		rc = -EIO;
-		goto out_err;
-	}
 
 	return 0;
 
@@ -451,9 +443,10 @@ static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
 		ordinal = be32_to_cpu(*((__be32 *) (buf + 6)));
 
 		dur = tpm_calc_ordinal_duration(chip, ordinal);
-		if (wait_for_tpm_stat
-		    (chip, TPM_STS_DATA_AVAIL | TPM_STS_VALID, dur,
-		     &priv->read_queue, false) < 0) {
+		if (tpm_tis_wait_for_stat(chip,
+					  TPM_STS_DATA_AVAIL | TPM_STS_VALID,
+					  TPM_STS_DATA_AVAIL | TPM_STS_VALID,
+					  dur, &priv->read_queue, false) < 0) {
 			rc = -ETIME;
 			goto out_err;
 		}
-- 
2.7.4