Re: [PATCH v7 01/11] tpm: Cap the number of PCR banks

Lai, Yi
2025-12-03T01:26:43Z

On Wed, Dec 03, 2025 at 03:11:54AM +0200, Jarkko Sakkinen wrote:
> On Wed, Dec 03, 2025 at 08:57:10AM +0800, Lai, Yi wrote:
> > On Thu, Nov 27, 2025 at 03:54:33PM +0200, Jarkko Sakkinen wrote:
> > > From: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>
> > >
> > > 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: Roberto Sassu <roberto.sassu@huawei.com>
> > > Fixes: bcfff8384f6c ("tpm: dynamically allocate the allocated_banks array")
> > > Reviewed-By: Jonathan McDowell <noodles@meta.com>
> > > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>
> > > ---
> > > v7:
> > > - In Ryzen desktop there is total three banks so yep, eight is probably
> > > much safer bet than four banks. Fixed the commit message as per remark
> > > from Jonathan:
> > >
> > > https://lore.kernel.org/linux-integrity/aPYg1N0TvrkG6AJI@earth.li/#t
> > >
> > > And with that added also reviewed-by.
> > > v6
> > > - No changes.
> > > v5:
> > > - No changes.
> > > v4:
> > > - Revert spurious changes from include/linux/tpm.h.
> > > - Increase TPM2_MAX_BANKS to 8.
> > > - Rename TPM2_MAX_BANKS as TPM2_MAX_PCR_BANKS for the sake of clarity.
> > > v3:
> > > - Wrote a more clear commit message.
> > > - Fixed pr_err() message.
> > > v2:
> > > - A new patch.
> > > ---
> > > drivers/char/tpm/tpm-chip.c | 13 +++++++++----
> > > drivers/char/tpm/tpm.h | 1 -
> > > drivers/char/tpm/tpm1-cmd.c | 25 -------------------------
> > > drivers/char/tpm/tpm2-cmd.c | 8 +++-----
> > > include/linux/tpm.h | 8 +++++---
> > > 5 files changed, 17 insertions(+), 38 deletions(-)
> > >
> > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > > index e25daf2396d3..6cb25862688f 100644
> > > --- a/drivers/char/tpm/tpm-chip.c
> > > +++ b/drivers/char/tpm/tpm-chip.c
> > > @@ -559,14 +559,19 @@ static int tpm_add_hwrng(struct tpm_chip *chip)
> > >
> > > static int tpm_get_pcr_allocation(struct tpm_chip *chip)
> > > {
> > > - int rc;
> > > + int rc = 0;
> > >
> > > if (tpm_is_firmware_upgrade(chip))
> > > return 0;
> > >
> > > - rc = (chip->flags & TPM_CHIP_FLAG_TPM2) ?
> > > - tpm2_get_pcr_allocation(chip) :
> > > - tpm1_get_pcr_allocation(chip);
> > > + if (!(chip->flags & TPM_CHIP_FLAG_TPM2)) {
> > > + 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;
> > > + chip->nr_allocated_banks = 1;
> > > + } else {
> > > + rc = tpm2_get_pcr_allocation(chip);
> > > + }
> > >
> > > if (rc > 0)
> > > return -ENODEV;
> > > diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> > > index 2726bd38e5ac..a37712c02e44 100644
> > > --- a/drivers/char/tpm/tpm.h
> > > +++ b/drivers/char/tpm/tpm.h
> > > @@ -252,7 +252,6 @@ int tpm1_pcr_read(struct tpm_chip *chip, u32 pcr_idx, u8 *res_buf);
> > > ssize_t tpm1_getcap(struct tpm_chip *chip, u32 subcap_id, cap_t *cap,
> > > const char *desc, size_t min_cap_length);
> > > int tpm1_get_random(struct tpm_chip *chip, u8 *out, size_t max);
> > > -int tpm1_get_pcr_allocation(struct tpm_chip *chip);
> > > unsigned long tpm_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
> > > int tpm_pm_suspend(struct device *dev);
> > > int tpm_pm_resume(struct device *dev);
> > > diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
> > > index 11088bda4e68..708bc553437b 100644
> > > --- a/drivers/char/tpm/tpm1-cmd.c
> > > +++ b/drivers/char/tpm/tpm1-cmd.c
> > > @@ -786,28 +786,3 @@ int tpm1_pm_suspend(struct tpm_chip *chip, u32 tpm_suspend_pcr)
> > >
> > > return rc;
> > > }
> > > -
> > > -/**
> > > - * tpm1_get_pcr_allocation() - initialize the allocated bank
> > > - * @chip: TPM chip to use.
> > > - *
> > > - * The function initializes the SHA1 allocated bank to extend PCR
> > > - *
> > > - * Return:
> > > - * * 0 on success,
> > > - * * < 0 on error.
> > > - */
> > > -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;
> > > - chip->nr_allocated_banks = 1;
> > > -
> > > - return 0;
> > > -}
> > > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> > > index 7d77f6fbc152..97501c567c34 100644
> > > --- a/drivers/char/tpm/tpm2-cmd.c
> > > +++ b/drivers/char/tpm/tpm2-cmd.c
> > > @@ -538,11 +538,9 @@ 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: unexpected number of banks: %u > %u",
> > > + nr_possible_banks, TPM2_MAX_PCR_BANKS);
> > > rc = -ENOMEM;
> > > goto out;
> > > }
> > > diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> > > index dc0338a783f3..eb0ff071bcae 100644
> > > --- 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 {
> > > @@ -189,7 +191,7 @@ 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
> > >
> >
> > Hi Jarkko Sakkinen,
> >
> > Greetings!
> >
> > I used Syzkaller and found that there is KASAN: invalid-free in tpm_dev_release in linux-tpmdd branch tpmdd-next-6.19-rc1-v3.
> >
> > After bisection and the first bad commit is:
> > "
> > 83f6ace27d21 tpm: Cap the number of PCR banks
>
> Thank you. I updated the patch in my branch:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git/commit/?id=bb731e948843a947b2b7e51552c1387e2c377e03
>

Re-test using the latest branch. Issue cannot be reproduced using the
same binary.

Regards,
Yi Lai

> Possible to re-test (I can add your tested-by afterwards)?
>
> BR, Jarkko