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

Nayna
2019-07-05T15:32:16Z

On 07/05/2019 10:13 AM, Stefan Berger wrote:
> 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;
>

Yes. I think I misread it. Thanks Stefan. Will fix this..

>
>
>
>
>> +    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);

I am not sure of the purpose of tpm_stop_chip(), so I have left it as it
is. Jarkko, what do you think about the change ?

Thanks & Regards,
- Nayna