[PATCH] tpm: Cap the number of PCR banks

[Jarkko Sakkinen <jarkko@kernel.org>]

From: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>

[ Upstream commit faf07e611dfa464b201223a7253e9dc5ee0f3c9e ]

tpm2_get_pcr_allocation() does not cap any upper limit for the number of
banks. Cap the limit to eight banks so that out of bounds values coming
from external I/O cause on only limited harm.

Cc: stable@vger.kernel.org # v5.10+
Fixes: bcfff8384f6c ("tpm: dynamically allocate the allocated_banks array")
Tested-by: Lai Yi <yi1.lai@linux.intel.com>
Reviewed-by: Jonathan McDowell <noodles@meta.com>
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>
---
Backport for v5.10, v5.15, v6.1 and v6.6
 drivers/char/tpm/tpm-chip.c | 1 -
 drivers/char/tpm/tpm1-cmd.c | 5 -----
 drivers/char/tpm/tpm2-cmd.c | 8 +++-----
 include/linux/tpm.h         | 8 +++++---
 4 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 70e3fe20fdcf..458a3e9ea73a 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -279,7 +279,6 @@ static void tpm_dev_release(struct device *dev)

 	kfree(chip->work_space.context_buf);
 	kfree(chip->work_space.session_buf);
-	kfree(chip->allocated_banks);
 	kfree(chip);
 }

diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index cf64c7385105..b49a790f1bd5 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -799,11 +799,6 @@ int tpm1_pm_suspend(struct tpm_chip *chip, u32 tpm_suspend_pcr)
  */
 int tpm1_get_pcr_allocation(struct tpm_chip *chip)
 {
-	chip->allocated_banks = kcalloc(1, sizeof(*chip->allocated_banks),
-					GFP_KERNEL);
-	if (!chip->allocated_banks)
-		return -ENOMEM;
-
 	chip->allocated_banks[0].alg_id = TPM_ALG_SHA1;
 	chip->allocated_banks[0].digest_size = hash_digest_size[HASH_ALGO_SHA1];
 	chip->allocated_banks[0].crypto_id = HASH_ALGO_SHA1;
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 93545be190a5..57bb3e34b770 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -574,11 +574,9 @@ ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)

 	nr_possible_banks = be32_to_cpup(
 		(__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
-
-	chip->allocated_banks = kcalloc(nr_possible_banks,
-					sizeof(*chip->allocated_banks),
-					GFP_KERNEL);
-	if (!chip->allocated_banks) {
+	if (nr_possible_banks > TPM2_MAX_PCR_BANKS) {
+		pr_err("tpm: out of bank capacity: %u > %u\n",
+		       nr_possible_banks, TPM2_MAX_PCR_BANKS);
 		rc = -ENOMEM;
 		goto out;
 	}
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index bf8a4ec8a01c..f5e7cca2f257 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -25,7 +25,9 @@
 #include <crypto/hash_info.h>

 #define TPM_DIGEST_SIZE 20	/* Max TPM v1.2 PCR size */
-#define TPM_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE
+
+#define TPM2_MAX_DIGEST_SIZE	SHA512_DIGEST_SIZE
+#define TPM2_MAX_PCR_BANKS	8

 struct tpm_chip;
 struct trusted_key_payload;
@@ -51,7 +53,7 @@ enum tpm_algorithms {

 struct tpm_digest {
 	u16 alg_id;
-	u8 digest[TPM_MAX_DIGEST_SIZE];
+	u8 digest[TPM2_MAX_DIGEST_SIZE];
 } __packed;

 struct tpm_bank_info {
@@ -157,7 +159,7 @@ struct tpm_chip {
 	unsigned int groups_cnt;

 	u32 nr_allocated_banks;
-	struct tpm_bank_info *allocated_banks;
+	struct tpm_bank_info allocated_banks[TPM2_MAX_PCR_BANKS];
 #ifdef CONFIG_ACPI
 	acpi_handle acpi_dev_handle;
 	char ppi_version[TPM_PPI_VERSION_LEN + 1];
--
2.52.0