Re: [PATCH v4 1/6] tpm: dynamically allocate active_banks array

[Roberto Sassu <roberto.sassu@huawei.com>]

On 11/7/2018 7:14 AM, Nayna Jain wrote:
> 
> 
> On 11/06/2018 08:31 PM, Roberto Sassu wrote:
>> This patch removes the hard-coded limit of the active_banks array size.
> 
> 
> The hard-coded limit in static array active_banks[] represents the 
> maximum possible banks.
> A TPM might have three banks, but only one bank may be active.
> 
> To confirm my understanding, is the idea for this patch is to 
> dynamically identify the number of possible banks or the number of 
> active banks ?

The idea is to dynamically identify the number of active banks.

In the TPM Commands specification (section 30.2.1), I found:

TPM_CAP_PCRS – Returns the current allocation of PCR in a
TPML_PCR_SELECTION.

You mentioned:

#TPM_RC_SIZE response code when count is greater
than the possible number of banks

but TPML_PCR_SELECTION is provided by the TPM.

Roberto


>> It stores in the tpm_chip structure the number of active PCR banks,
>> determined in tpm2_get_pcr_allocation(), and replaces the static array
>> with a pointer to a dynamically allocated array.
>>
>> As a consequence of the introduction of nr_active_banks, tpm_pcr_extend()
>> does not check anymore if the algorithm stored in tpm_chip is equal to
>> zero. The active_banks array always contains valid algorithms.
>>
>> Fixes: 1db15344f874 ("tpm: implement TPM 2.0 capability to get active
>> PCR banks")
>>
>> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
>> ---
>>   drivers/char/tpm/tpm-chip.c      |  1 +
>>   drivers/char/tpm/tpm-interface.c | 19 ++++++++++++-------
>>   drivers/char/tpm/tpm.h           |  3 ++-
>>   drivers/char/tpm/tpm2-cmd.c      | 17 ++++++++---------
>>   4 files changed, 23 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
>> index 46caadca916a..2a9e8b744436 100644
>> --- a/drivers/char/tpm/tpm-chip.c
>> +++ b/drivers/char/tpm/tpm-chip.c
>> @@ -160,6 +160,7 @@ static void tpm_dev_release(struct device *dev)
>>       kfree(chip->log.bios_event_log);
>>       kfree(chip->work_space.context_buf);
>>       kfree(chip->work_space.session_buf);
>> +    kfree(chip->active_banks);
>>       kfree(chip);
>>   }
>>
>> diff --git a/drivers/char/tpm/tpm-interface.c 
>> b/drivers/char/tpm/tpm-interface.c
>> index 1a803b0cf980..ba7ca6b3e664 100644
>> --- a/drivers/char/tpm/tpm-interface.c
>> +++ b/drivers/char/tpm/tpm-interface.c
>> @@ -1039,8 +1039,7 @@ static int tpm1_pcr_extend(struct tpm_chip 
>> *chip, int pcr_idx, const u8 *hash,
>>   int tpm_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash)
>>   {
>>       int rc;
>> -    struct tpm2_digest digest_list[ARRAY_SIZE(chip->active_banks)];
>> -    u32 count = 0;
>> +    struct tpm2_digest *digest_list;
>>       int i;
>>
>>       chip = tpm_find_get_ops(chip);
>> @@ -1048,16 +1047,22 @@ int tpm_pcr_extend(struct tpm_chip *chip, int 
>> pcr_idx, const u8 *hash)
>>           return -ENODEV;
>>
>>       if (chip->flags & TPM_CHIP_FLAG_TPM2) {
>> -        memset(digest_list, 0, sizeof(digest_list));
>> +        digest_list = kmalloc_array(chip->nr_active_banks,
>> +                        sizeof(*digest_list), GFP_KERNEL);
>> +        if (!digest_list)
>> +            return -ENOMEM;
>>
>> -        for (i = 0; i < ARRAY_SIZE(chip->active_banks) &&
>> -                chip->active_banks[i] != TPM2_ALG_ERROR; i++) {
>> +        memset(digest_list, 0,
>> +               chip->nr_active_banks * sizeof(*digest_list));
>> +
>> +        for (i = 0; i < chip->nr_active_banks; i++) {
>>               digest_list[i].alg_id = chip->active_banks[i];
>>               memcpy(digest_list[i].digest, hash, TPM_DIGEST_SIZE);
>> -            count++;
>>           }
>>
>> -        rc = tpm2_pcr_extend(chip, pcr_idx, count, digest_list);
>> +        rc = tpm2_pcr_extend(chip, pcr_idx, chip->nr_active_banks,
>> +                     digest_list);
>> +        kfree(digest_list);
>>           tpm_put_ops(chip);
>>           return rc;
>>       }
>> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
>> index f3501d05264f..98368c3a6ff7 100644
>> --- a/drivers/char/tpm/tpm.h
>> +++ b/drivers/char/tpm/tpm.h
>> @@ -248,7 +248,8 @@ struct tpm_chip {
>>       const struct attribute_group *groups[3];
>>       unsigned int groups_cnt;
>>
>> -    u16 active_banks[7];
>> +    u32 nr_active_banks;
>> +    u16 *active_banks;
>>   #ifdef CONFIG_ACPI
>>       acpi_handle acpi_dev_handle;
>>       char ppi_version[TPM_PPI_VERSION_LEN + 1];
>> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
>> index c31b490bd41d..533089cede07 100644
>> --- a/drivers/char/tpm/tpm2-cmd.c
>> +++ b/drivers/char/tpm/tpm2-cmd.c
>> @@ -242,7 +242,7 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int 
>> pcr_idx, u32 count,
>>       int i;
>>       int j;
>>
>> -    if (count > ARRAY_SIZE(chip->active_banks))
>> +    if (count > chip->nr_active_banks)
>>           return -EINVAL;
>>
>>       rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
>> @@ -859,7 +859,6 @@ static ssize_t tpm2_get_pcr_allocation(struct 
>> tpm_chip *chip)
>>       void *marker;
>>       void *end;
>>       void *pcr_select_offset;
>> -    unsigned int count;
>>       u32 sizeof_pcr_selection;
>>       u32 rsp_len;
>>       int rc;
>> @@ -878,11 +877,14 @@ static ssize_t tpm2_get_pcr_allocation(struct 
>> tpm_chip *chip)
>>       if (rc)
>>           goto out;
>>
>> -    count = be32_to_cpup(
>> +    chip->nr_active_banks = be32_to_cpup(
>>           (__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
> 
> 
> As per my understanding, the count in the TPML_PCR_SELECTION represent 
> the number of possible banks and not the number of active banks.
> TCG Structures Spec for TPM 2.0 - Table 102 mentions this as explanation 
> of #TPM_RC_SIZE.
> 
> Thanks & Regards,
>      - Nayna
> 
> 
>>
>> -    if (count > ARRAY_SIZE(chip->active_banks)) {
>> -        rc = -ENODEV;
>> +    chip->active_banks = kmalloc_array(chip->nr_active_banks,
>> +                       sizeof(*chip->active_banks),
>> +                       GFP_KERNEL);
>> +    if (!chip->active_banks) {
>> +        rc = -ENOMEM;
>>           goto out;
>>       }
>>
>> @@ -891,7 +893,7 @@ static ssize_t tpm2_get_pcr_allocation(struct 
>> tpm_chip *chip)
>>       rsp_len = be32_to_cpup((__be32 *)&buf.data[2]);
>>       end = &buf.data[rsp_len];
>>
>> -    for (i = 0; i < count; i++) {
>> +    for (i = 0; i < chip->nr_active_banks; i++) {
>>           pcr_select_offset = marker +
>>               offsetof(struct tpm2_pcr_selection, size_of_select);
>>           if (pcr_select_offset >= end) {
>> @@ -908,9 +910,6 @@ static ssize_t tpm2_get_pcr_allocation(struct 
>> tpm_chip *chip)
>>       }
>>
>>   out:
>> -    if (i < ARRAY_SIZE(chip->active_banks))
>> -        chip->active_banks[i] = TPM2_ALG_ERROR;
>> -
>>       tpm_buf_destroy(&buf);
>>
>>       return rc;
> 

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