linux-kernel - [PATCH v3] KEYS: trusted: correctly initialize digests and fix locking issue

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Message-ID: <20190908174542.509-1-roberto.sassu@huawei.com>
Date:   Sun, 8 Sep 2019 19:45:42 +0200
From:   Roberto Sassu <roberto.sassu@...wei.com>
To:     <jarkko.sakkinen@...ux.intel.com>, <zohar@...ux.ibm.com>
CC:     <linux-integrity@...r.kernel.org>,
        <linux-security-module@...r.kernel.org>,
        <keyrings@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <silviu.vlasceanu@...wei.com>,
        Roberto Sassu <roberto.sassu@...wei.com>
Subject: [PATCH v3] KEYS: trusted: correctly initialize digests and fix locking issue

Commit 0b6cf6b97b7e ("tpm: pass an array of tpm_extend_digest structures to
tpm_pcr_extend()") modifies tpm_pcr_extend() to accept a digest for each
PCR bank. After modification, tpm_pcr_extend() expects that digests are
passed in the same order as the algorithms set in chip->allocated_banks.

This patch fixes two issues introduced in the last iterations of the patch
set: missing initialization of the TPM algorithm ID in the tpm_digest
structures passed to tpm_pcr_extend() by the trusted key module, and
unreleased locks in the TPM driver due to returning from tpm_pcr_extend()
without calling tpm_put_ops(). To avoid the second issue, input check is
done before locks are taken.

Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
Fixes: 0b6cf6b97b7e ("tpm: pass an array of tpm_extend_digest structures to tpm_pcr_extend()")
---
Changelog

v2:
- provide explanation of the problem

v1:
- correct referenced commit

 drivers/char/tpm/tpm-interface.c | 8 ++++----
 security/keys/trusted.c          | 5 +++++
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 1b4f95c13e00..1fffa91fc148 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -316,14 +316,14 @@ int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
 	int rc;
 	int i;
 
-	chip = tpm_find_get_ops(chip);
-	if (!chip)
-		return -ENODEV;
-
 	for (i = 0; i < chip->nr_allocated_banks; i++)
 		if (digests[i].alg_id != chip->allocated_banks[i].alg_id)
 			return -EINVAL;
 
+	chip = tpm_find_get_ops(chip);
+	if (!chip)
+		return -ENODEV;
+
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
 		rc = tpm2_pcr_extend(chip, pcr_idx, digests);
 		tpm_put_ops(chip);
diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index ade699131065..1fbd77816610 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -1228,11 +1228,16 @@ static int __init trusted_shash_alloc(void)
 
 static int __init init_digests(void)
 {
+	int i;
+
 	digests = kcalloc(chip->nr_allocated_banks, sizeof(*digests),
 			  GFP_KERNEL);
 	if (!digests)
 		return -ENOMEM;
 
+	for (i = 0; i < chip->nr_allocated_banks; i++)
+		digests[i].alg_id = chip->allocated_banks[i].alg_id;
+
 	return 0;
 }
 
-- 
2.17.1