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* [PATCH v2] tpm: Replace WARN_ONCE() with dev_err_once() in tpm_tis_status()
@ 2021-05-31  5:34 Jarkko Sakkinen
  2021-05-31  5:50 ` Greg KH
  0 siblings, 1 reply; 3+ messages in thread
From: Jarkko Sakkinen @ 2021-05-31  5:34 UTC (permalink / raw)
  To: linux-integrity
  Cc: Jarkko Sakkinen, stable, Hans de Goede, Greg KH, Peter Huewe,
	Jason Gunthorpe, James Bottomley

Do not torn down the system when getting invalid status from a TPM chip.
This can happen when panic-on-warn is used.

In addition, print out the value of TPM_STS.x instead of "invalid
status". In order to get the earlier benefits for forensics, also call
dump_stack().

Link: https://lore.kernel.org/keyrings/YKzlTR1AzUigShtZ@kroah.com/
Fixes: 55707d531af6 ("tpm_tis: Add a check for invalid status")
Cc: stable@vger.kernel.org
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---

v2:
Dump also stack only once.

 drivers/char/tpm/tpm_tis_core.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 55b9d3965ae1..ce410f19eff2 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -188,21 +188,33 @@ static int request_locality(struct tpm_chip *chip, int l)
 static u8 tpm_tis_status(struct tpm_chip *chip)
 {
 	struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
-	int rc;
+	static unsigned long klog_once;
 	u8 status;
+	int rc;
 
 	rc = tpm_tis_read8(priv, TPM_STS(priv->locality), &status);
 	if (rc < 0)
 		return 0;
 
 	if (unlikely((status & TPM_STS_READ_ZERO) != 0)) {
-		/*
-		 * If this trips, the chances are the read is
-		 * returning 0xff because the locality hasn't been
-		 * acquired.  Usually because tpm_try_get_ops() hasn't
-		 * been called before doing a TPM operation.
-		 */
-		WARN_ONCE(1, "TPM returned invalid status\n");
+		if  (!test_and_set_bit(BIT(0), &klog_once)) {
+			/*
+			 * If this trips, the chances are the read is
+			 * returning 0xff because the locality hasn't been
+			 * acquired.  Usually because tpm_try_get_ops() hasn't
+			 * been called before doing a TPM operation.
+			 */
+			dev_err(&chip->dev, "invalid TPM_STS.x 0x%02x, dumping stack for forensics\n",
+				status);
+
+			/*
+			 * Dump stack for forensics, as invalid TPM_STS.x could be
+			 * potentially triggered by impaired tpm_try_get_ops() or
+			 * tpm_find_get_ops().
+			 */
+			dump_stack();
+		}
+
 		return 0;
 	}
 
-- 
2.31.1


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2021-05-31  5:34 [PATCH v2] tpm: Replace WARN_ONCE() with dev_err_once() in tpm_tis_status() Jarkko Sakkinen
2021-05-31  5:50 ` Greg KH
2021-06-01 17:43   ` Jarkko Sakkinen

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