tpm: pass an array of tpm_extend_digest structures to tpm_pcr_extend()

Currently, tpm_pcr_extend() accepts as an input only a SHA1 digest.

This patch replaces the hash parameter of tpm_pcr_extend() with an array of
tpm_digest structures, so that the caller can provide a digest for each PCR
bank currently allocated in the TPM.

tpm_pcr_extend() will not extend banks for which no digest was provided,
as it happened before this patch, but instead it requires that callers
provide the full set of digests. Since the number of digests will always be
chip->nr_allocated_banks, the count parameter has been removed.

Due to the API change, ima_pcr_extend() and pcrlock() have been modified.
Since the number of allocated banks is not known in advance, the memory for
the digests must be dynamically allocated. To avoid performance degradation
and to avoid that a PCR extend is not done due to lack of memory, the array
of tpm_digest structures is allocated by the users of the TPM driver at
initialization time.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Mimi Zohar <zohar@linux.ibm.com> (on x86 for TPM 1.2 & PTT TPM 2.0)
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

1 files changed, 11 insertions, 19 deletions

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 1c92dbeef736..83ece5639f86 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -308,42 +308,34 @@ EXPORT_SYMBOL_GPL(tpm_pcr_read);
  * tpm_pcr_extend - extend a PCR value in SHA1 bank.
  * @chip:	a &struct tpm_chip instance, %NULL for the default chip
  * @pcr_idx:	the PCR to be retrieved
- * @hash:	the hash value used to extend the PCR value
+ * @digests:	array of tpm_digest structures used to extend PCRs
  *
- * Note: with TPM 2.0 extends also those banks for which no digest was
- * specified in order to prevent malicious use of those PCR banks.
+ * Note: callers must pass a digest for every allocated PCR bank, in the same
+ * order of the banks in chip->allocated_banks.
  *
  * Return: same as with tpm_transmit_cmd()
  */
-int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash)
+int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
+		   struct tpm_digest *digests)
 {
 	int rc;
-	struct tpm_digest *digest_list;
 	int i;
 
 	chip = tpm_find_get_ops(chip);
 	if (!chip)
 		return -ENODEV;
 
-	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
-		digest_list = kcalloc(chip->nr_allocated_banks,
-				      sizeof(*digest_list), GFP_KERNEL);
-		if (!digest_list)
-			return -ENOMEM;
-
-		for (i = 0; i < chip->nr_allocated_banks; i++) {
-			digest_list[i].alg_id = chip->allocated_banks[i].alg_id;
-			memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
-		}
+	for (i = 0; i < chip->nr_allocated_banks; i++)
+		if (digests[i].alg_id != chip->allocated_banks[i].alg_id)
+			return -EINVAL;
 
-		rc = tpm2_pcr_extend(chip, pcr_idx, chip->nr_allocated_banks,
-				     digest_list);
-		kfree(digest_list);
+	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+		rc = tpm2_pcr_extend(chip, pcr_idx, digests);
 		tpm_put_ops(chip);
 		return rc;
 	}
 
-	rc = tpm1_pcr_extend(chip, pcr_idx, hash,
+	rc = tpm1_pcr_extend(chip, pcr_idx, digests[0].digest,
 			     "attempting extend a PCR value");
 	tpm_put_ops(chip);
 	return rc;