[PATCH 6.12 166/567] tpm: Cap the number of PCR banks

Greg Kroah-Hartman
2026-01-06T17:23:30Z

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

commit faf07e611dfa464b201223a7253e9dc5ee0f3c9e upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
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(-)

--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -282,7 +282,6 @@ static void tpm_dev_release(struct devic

kfree(chip->work_space.context_buf);
kfree(chip->work_space.session_buf);
- kfree(chip->allocated_banks);
#ifdef CONFIG_TCG_TPM2_HMAC
kfree(chip->auth);
#endif
--- 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 *chi
*/
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;
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -602,11 +602,9 @@ ssize_t tpm2_get_pcr_allocation(struct t

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;
}
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -26,7 +26,9 @@
#include <crypto/aes.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;
@@ -68,7 +70,7 @@ enum tpm2_curves {

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

struct tpm_bank_info {
@@ -188,7 +190,7 @@ 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];