linux-kernel - [PATCH 4.11 007/197] tpm_tis_core: Choose appropriate timeout for reading burstcount

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Date:   Tue, 23 May 2017 22:06:08 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Alexander Steffen <Alexander.Steffen@...ineon.com>,
        Peter Huewe <peter.huewe@...ineon.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Subject: [PATCH 4.11 007/197] tpm_tis_core: Choose appropriate timeout for reading burstcount

4.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Alexander Steffen <Alexander.Steffen@...ineon.com>

commit 302a6ad7fc77146191126a1f3e2c5d724fd72416 upstream.

TIS v1.3 for TPM 1.2 and PTP for TPM 2.0 disagree about which timeout
value applies to reading a valid burstcount. It is TIMEOUT_D according to
TIS, but TIMEOUT_A according to PTP, so choose the appropriate value
depending on whether we deal with a TPM 1.2 or a TPM 2.0.

This is important since according to the PTP TIMEOUT_D is much smaller
than TIMEOUT_A. So the previous implementation could run into timeouts
with a TPM 2.0, even though the TPM was behaving perfectly fine.

During tpm2_probe TIMEOUT_D will be used even with a TPM 2.0, because
TPM_CHIP_FLAG_TPM2 is not yet set. This is fine, since the timeout values
will only be changed afterwards by tpm_get_timeouts. Until then
TIS_TIMEOUT_D_MAX applies, which is large enough.

Fixes: aec04cbdf723 ("tpm: TPM 2.0 FIFO Interface")
Signed-off-by: Alexander Steffen <Alexander.Steffen@...ineon.com>
Signed-off-by: Peter Huewe <peter.huewe@...ineon.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/char/tpm/tpm_tis_core.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -160,8 +160,10 @@ static int get_burstcount(struct tpm_chi
 	u32 value;

 	/* wait for burstcount */
-	/* which timeout value, spec has 2 answers (c & d) */
-	stop = jiffies + chip->timeout_d;
+	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+		stop = jiffies + chip->timeout_a;
+	else
+		stop = jiffies + chip->timeout_d;
 	do {
 		rc = tpm_tis_read32(priv, TPM_STS(priv->locality), &value);
 		if (rc < 0)