linux-kernel - [PATCH v12 7/9] tpm: tpm_tis: verify TPM_STS register is valid after locality request

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Message-Id: <20200625144650.269719-8-amirmizi6@gmail.com>
Date:   Thu, 25 Jun 2020 17:46:47 +0300
From:   amirmizi6@...il.com
To:     Eyal.Cohen@...oton.com, jarkko.sakkinen@...ux.intel.com,
        oshrialkoby85@...il.com, alexander.steffen@...ineon.com,
        robh+dt@...nel.org,
        "benoit.houyere@...com--to=mark.rutland"@arm.com,
        peterhuewe@....de, christophe-h.richard@...com, jgg@...pe.ca,
        arnd@...db.de, gregkh@...uxfoundation.org
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-integrity@...r.kernel.org, oshri.alkoby@...oton.com,
        tmaimon77@...il.com, gcwilson@...ibm.com, kgoldman@...ibm.com,
        Dan.Morav@...oton.com, oren.tanami@...oton.com,
        shmulik.hager@...oton.com, amir.mizinski@...oton.com,
        Amir Mizinski <amirmizi6@...il.com>,
        Benoit Houyere <benoit.houyere@...com>
Subject: [PATCH v12 7/9] tpm: tpm_tis: verify TPM_STS register is valid after locality request

From: Amir Mizinski <amirmizi6@...il.com>

Issue could result when the TPM does not update TPM_STS register after
a locality request (TPM_STS Initial value = 0xFF) and a TPM_STS register
read occurs (tpm_tis_status(chip)).

Checking the next condition("if ((status & TPM_STS_COMMAND_READY) == 0)"),
the status will be at 0xFF and will be considered, wrongly, in "Ready"
state (by checking only one bit). However, at this moment the TPM is, in
fact, in "Idle" state and remains in "Idle" state because
"tpm_tis_ready(chip);" was not executed.

Suggested-by: Benoit Houyere <benoit.houyere@...com>
Signed-off-by: Amir Mizinski <amirmizi6@...il.com>
---
 drivers/char/tpm/tpm_tis_core.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index a38465f..b876db2 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -221,8 +221,14 @@ static int request_locality(struct tpm_chip *chip, int l)
 	} else {
 		/* wait for burstcount */
 		do {
-			if (check_locality(chip, l))
+			if (check_locality(chip, l)) {
+				if (wait_for_tpm_stat(chip, TPM_STS_GO, 0,
+						      chip->timeout_c,
+						      &priv->int_queue,
+						      false) < 0)
+					return -ETIME;
 				return l;
+			}
 			tpm_msleep(TPM_TIMEOUT);
 		} while (time_before(jiffies, stop));
 	}
-- 
2.7.4