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Message-ID: <da2ef557-3041-a1ca-47cb-fd7ab92876aa@huawei.com>
Date: Wed, 7 Nov 2018 10:41:57 +0100
From: Roberto Sassu <roberto.sassu@...wei.com>
To: Nayna Jain <nayna@...ux.ibm.com>,
<jarkko.sakkinen@...ux.intel.com>, <zohar@...ux.ibm.com>
CC: <linux-integrity@...r.kernel.org>,
<linux-security-module@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <silviu.vlasceanu@...wei.com>
Subject: Re: [PATCH v4 1/6] tpm: dynamically allocate active_banks array
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@...wei.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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