tpm: dynamically allocate the allocated_banks array

This patch renames active_banks (member of tpm_chip) to allocated_banks,
stores the number of allocated PCR banks in nr_allocated_banks (new member
of tpm_chip), and replaces the static array with a pointer to a dynamically
allocated array.

tpm2_get_pcr_allocation() determines if a PCR bank is allocated by checking
the mask in the TPML_PCR_SELECTION structure returned by the TPM for
TPM2_Get_Capability(). If a bank is not allocated, the TPM returns that
bank in TPML_PCR_SELECTION, with all bits in the mask set to zero. In this
case, the bank is not included in chip->allocated_banks, to avoid that TPM
driver users unnecessarily calculate a digest for that bank.

One PCR bank with algorithm set to SHA1 is always allocated for TPM 1.x.

As a consequence of the introduction of nr_allocated_banks,
tpm_pcr_extend() does not check anymore if the algorithm stored in tpm_chip
is equal to zero.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

1 files changed, 10 insertions, 8 deletions

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 498809bf1bf0..2b31eff06b0e 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -318,8 +318,7 @@ EXPORT_SYMBOL_GPL(tpm_pcr_read);
 int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash)
 {
 	int rc;
-	struct tpm2_digest digest_list[ARRAY_SIZE(chip->active_banks)];
-	u32 count = 0;
+	struct tpm2_digest *digest_list;
 	int i;
 
 	chip = tpm_find_get_ops(chip);
@@ -327,16 +326,19 @@ int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash)
 		return -ENODEV;
 
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
-		memset(digest_list, 0, sizeof(digest_list));
+		digest_list = kcalloc(chip->nr_allocated_banks,
+				      sizeof(*digest_list), GFP_KERNEL);
+		if (!digest_list)
+			return -ENOMEM;
 
-		for (i = 0; i < ARRAY_SIZE(chip->active_banks) &&
-			    chip->active_banks[i] != TPM2_ALG_ERROR; i++) {
-			digest_list[i].alg_id = chip->active_banks[i];
+		for (i = 0; i < chip->nr_allocated_banks; i++) {
+			digest_list[i].alg_id = chip->allocated_banks[i];
 			memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
-			count++;
 		}
 
-		rc = tpm2_pcr_extend(chip, pcr_idx, count, digest_list);
+		rc = tpm2_pcr_extend(chip, pcr_idx, chip->nr_allocated_banks,
+				     digest_list);
+		kfree(digest_list);
 		tpm_put_ops(chip);
 		return rc;
 	}