[PATCH v3] tpm: Replace WARN_ONCE() with dev_err_once() in tpm_tis_status()

Jarkko Sakkinen
2021-06-09T13:26:27Z

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

Instead, introduce TPM_TIS_INVALID_STATUS bitflag and use it to trigger
once the error reporting per chip. In addition, print out the value of
TPM_STS for improved forensics.

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>
---

v3:
* torn -> tear
* A per chip flag TPM_TIS_INVALID_STATUS.

v2:
Dump also stack only once.

drivers/char/tpm/tpm_tis_core.c | 25 ++++++++++++++++++-------
drivers/char/tpm/tpm_tis_core.h | 3 ++-
2 files 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..69579efb247b 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -196,13 +196,24 @@ static u8 tpm_tis_status(struct tpm_chip *chip)
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(TPM_TIS_INVALID_STATUS, &priv->flags)) {
+ /*
+ * 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;
}

diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
index 9b2d32a59f67..b2a3c6c72882 100644
--- a/drivers/char/tpm/tpm_tis_core.h
+++ b/drivers/char/tpm/tpm_tis_core.h
@@ -83,6 +83,7 @@ enum tis_defaults {

enum tpm_tis_flags {
TPM_TIS_ITPM_WORKAROUND = BIT(0),
+ TPM_TIS_INVALID_STATUS = BIT(1),
};

struct tpm_tis_data {
@@ -90,7 +91,7 @@ struct tpm_tis_data {
int locality;
int irq;
bool irq_tested;
- unsigned int flags;
+ unsigned long flags;
void __iomem *ilb_base_addr;
u16 clkrun_enabled;
wait_queue_head_t int_queue;
--
2.31.1