Re: [PATCH] tpm: fixes uninitialized allocated banks for IBM vtpm driver

Stefan Berger
2019-07-05T14:15:21Z

On 7/3/19 11:32 PM, Nayna Jain wrote:
> The nr_allocated_banks and allocated banks are initialized as part of
> tpm_chip_register. Currently, this is done as part of auto startup
> function. However, some drivers, like the ibm vtpm driver, do not run
> auto startup during initialization. This results in uninitialized memory
> issue and causes a kernel panic during boot.
>
> This patch moves the pcr allocation outside the auto startup function
> into tpm_chip_register. This ensures that allocated banks are initialized
> in any case.
>
> Fixes: 879b589210a9 ("tpm: retrieve digest size of unknown algorithms with
> PCR read")
> Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
> ---
> drivers/char/tpm/tpm-chip.c | 37 +++++++++++++++++++++++++++++++++++++
> drivers/char/tpm/tpm.h | 1 +
> drivers/char/tpm/tpm1-cmd.c | 12 ------------
> drivers/char/tpm/tpm2-cmd.c | 6 +-----
> 4 files changed, 39 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 8804c9e916fd..958508bb8379 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -550,6 +550,39 @@ static int tpm_add_hwrng(struct tpm_chip *chip)
> return hwrng_register(&chip->hwrng);
> }
>
> +/*
> + * tpm_pcr_allocation() - initializes the chip allocated banks for PCRs
> + */
> +static int tpm_pcr_allocation(struct tpm_chip *chip)
> +{
> + int rc = 0;
> +
> + if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> + rc = tpm2_get_pcr_allocation(chip);
> + if (rc)
> + goto out;
> + }
> +
> + /* Initialize TPM 1.2 */
> + chip->allocated_banks = kcalloc(1, sizeof(*chip->allocated_banks),
> + GFP_KERNEL);
> + if (!chip->allocated_banks) {
> + rc = -ENOMEM;
> + goto out;
> + }
> +
> + 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;
> +out:
> + if (rc < 0)
> + rc = -ENODEV;

The old code where you lifted this from said:

out:
if (rc > 0)
rc = -ENODEV;
return rc;

It would not overwrite -ENOMEM with -ENODEV but yours does.

I think the correct fix would be to use:

if (rc > 0)

rc = -ENODEV;

> + return rc;
> +}
> +
> /*
> * tpm_chip_register() - create a character device for the TPM chip
> * @chip: TPM chip to use.
> @@ -573,6 +606,10 @@ int tpm_chip_register(struct tpm_chip *chip)
> if (rc)
> return rc;

Above this is tpm_chip_stop(chip) because (afaik) none of the following
function calls in tpm_chip_register() needed the TPM, but now with
tpm_pcr_allocation() you will need to send a command to the TPM. So I
would say you should move the tpm_chip_stop() into the error branch
visible above and also after the tpm_pcr_allocation().

> + rc = tpm_pcr_allocation(chip);
tpm_chip_stop(chip);
> + if (rc)
> + return rc;
> +
> tpm_sysfs_add_device(chip);
>
> rc = tpm_bios_log_setup(chip);

Stefan