linux-kernel - [PATCH v3] tpm: check selftest status before retrying full selftest

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Message-Id: <20180515071712.9331-1-nayna@linux.vnet.ibm.com>
Date:   Tue, 15 May 2018 12:47:12 +0530
From:   Nayna Jain <nayna@...ux.vnet.ibm.com>
To:     linux-integrity@...r.kernel.org
Cc:     zohar@...ux.vnet.ibm.com, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, peterhuewe@....de,
        jarkko.sakkinen@...ux.intel.com, tpmdd@...horst.net,
        jgunthorpe@...idianresearch.com,
        Nayna Jain <nayna@...ux.vnet.ibm.com>
Subject: [PATCH v3] tpm: check selftest status before retrying full selftest

TPM 2.0 supports TPM2_GetTestResult[1], which can be used to check the
selftest status. This patch implements the tpm2_get_selftest_result()
function to check the selftest status before trying full selftest.

[1] As per TCG Specification, Trusted Platform Module Library,
Part 2 - Commands, Section 10.4:

"This command(TPM2_GetTestResult) returns manufacturer-specific information
regarding the results of a self-test and an indication of the test status.

Signed-off-by: Nayna Jain <nayna@...ux.vnet.ibm.com>
Tested-by: Mimi Zohar <zohar@...ux.vnet.ibm.com> (on Pi with TPM 2.0)
Tested-by: Stefan Berger <stefanb@...ux.vnet.ibm.com> (With QEMU with
swtpm TPM 2.0)
---

Changelog:

v3:
* modified to check the selftest status before full selftest command is run
* fixed the patch description
* includes Jarkko's feedbacks

v2:
* changed the subject and updated patch description
* removed the logs

 drivers/char/tpm/tpm.h      |  2 ++
 drivers/char/tpm/tpm2-cmd.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 46 insertions(+)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index af3bb87d3ea1..1de4240b52c4 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -114,6 +114,7 @@ enum tpm2_return_codes {
 	TPM2_RC_FAILURE		= 0x0101,
 	TPM2_RC_DISABLED	= 0x0120,
 	TPM2_RC_COMMAND_CODE    = 0x0143,
+	TPM2_RC_NEEDS_TEST      = 0x0153,
 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
 	TPM2_RC_REFERENCE_H0	= 0x0910,
 	TPM2_RC_RETRY		= 0x0922,
@@ -144,6 +145,7 @@ enum tpm2_command_codes {
 	TPM2_CC_FLUSH_CONTEXT	= 0x0165,
 	TPM2_CC_GET_CAPABILITY	= 0x017A,
 	TPM2_CC_GET_RANDOM	= 0x017B,
+	TPM2_CC_GET_TEST_RESULT = 0x017C,
 	TPM2_CC_PCR_READ	= 0x017E,
 	TPM2_CC_PCR_EXTEND	= 0x0182,
 	TPM2_CC_LAST		= 0x018F,
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 96c77c8e7f40..811bcf221208 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -825,6 +825,43 @@ unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal)
 EXPORT_SYMBOL_GPL(tpm2_calc_ordinal_duration);
 
 /**
+ * tpm2_get_selftest_result() - get the status of selftest
+ * @chip: TPM chip to use
+ *
+ * Return: TPM return code, errno otherwise
+ */
+static int tpm2_get_selftest_result(struct tpm_chip *chip)
+{
+	struct tpm_buf buf;
+	int rc;
+	int test_result;
+	uint16_t data_size;
+	int len;
+	const struct tpm_output_header *header;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_TEST_RESULT);
+	if (rc)
+		return rc;
+
+	len = tpm_transmit(chip, NULL, buf.data, PAGE_SIZE, 0);
+	if (len <  0)
+		return len;
+
+	header = (struct tpm_output_header *)buf.data;
+
+	rc = be32_to_cpu(header->return_code);
+	if (rc)
+		return rc;
+
+	data_size = be16_to_cpup((__be16 *)&buf.data[TPM_HEADER_SIZE]);
+
+	test_result = be32_to_cpup((__be32 *)
+			(&buf.data[TPM_HEADER_SIZE + 2 + data_size]));
+
+	return test_result;
+}
+
+/**
  * tpm2_do_selftest() - ensure that all self tests have passed
  *
  * @chip: TPM chip to use
@@ -857,6 +894,13 @@ static int tpm2_do_selftest(struct tpm_chip *chip)
 			rc = TPM2_RC_SUCCESS;
 		if (rc == TPM2_RC_INITIALIZE || rc == TPM2_RC_SUCCESS)
 			return rc;
+
+		rc = tpm2_get_selftest_result(chip);
+		dev_dbg(&chip->dev, "self test result is %04x\n", rc);
+
+		if (rc == TPM2_RC_TESTING || rc == TPM2_RC_SUCCESS)
+			return TPM2_RC_SUCCESS;
+
 	}
 
 	return rc;
-- 
2.13.6