Re: [PATCH] tpm: Replace WARN_ONCE() with dev_err_once() in tpm_tis_status()

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Dear Jarkko,


Am 31.05.21 um 06:51 schrieb Jarkko Sakkinen:
Do not torn down the system when getting invalid status from a TPM chip.

Nit: Do not *tear* down …?

This can happen when panic-on-warn is used.

Hmm, I’d say it works as expected then? Shouldn’t an invalid status of an important device like TPM considered a warning?

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@xxxxxxxxx/
Fixes: 55707d531af6 ("tpm_tis: Add a check for invalid status")
Cc: stable@xxxxxxxxxxxxxxx
Cc: Hans de Goede <hdegoede@xxxxxxxxxx>
Cc: Greg KH <greg@xxxxxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>
---
  drivers/char/tpm/tpm_tis_core.c | 11 ++++++++++-
  1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index 55b9d3965ae1..514a481829c9 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -202,7 +202,16 @@ static u8 tpm_tis_status(struct tpm_chip *chip)
  		 * acquired.  Usually because tpm_try_get_ops() hasn't
  		 * been called before doing a TPM operation.
  		 */
-		WARN_ONCE(1, "TPM returned invalid status\n");
+		dev_err_once(&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;
  	}


Kind regards,

Paul



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