Re: [PATCH] tpm_tis_core: Choose appropriate timeout for reading burstcount
From: Jarkko Sakkinen <hidden>
Date: 2017-02-24 17:41:51
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On Thu, Feb 16, 2017 at 03:33:36PM +0000, Peter Huewe wrote:
From: Alexander Steffen <redacted>
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.
Cc: stable@vger.kernel.org
Fixes: aec04cbdf723 ("tpm: TPM 2.0 FIFO Interface")
Signed-off-by: Alexander Steffen <redacted>
Signed-off-by: Peter Huewe <redacted>Pushed. /Jarkko
quoted hunk ↗ jump to hunk
--- drivers/char/tpm/tpm_tis_core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c index c0f296b5d413..fc0e9a2734ed 100644 --- 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_chip *chip) 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)-- 2.7.4