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

[Stefan Berger <stefanb@linux.ibm.com>]

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