Re: [PATCH v7 1/5] tpm: dynamically allocate the allocated_banks array

From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Roberto Sassu <roberto.sassu@huawei.com>
Cc: zohar@linux.ibm.com, david.safford@ge.com, monty.wiseman@ge.com,
	linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org, silviu.vlasceanu@huawei.com
Subject: Re: [PATCH v7 1/5] tpm: dynamically allocate the allocated_banks array
Date: Thu, 20 Dec 2018 16:55:00 +0200	[thread overview]
Message-ID: <20181220145500.GA10652@linux.intel.com> (raw)
In-Reply-To: <20181213102945.30946-2-roberto.sassu@huawei.com>

On Thu, Dec 13, 2018 at 11:29:41AM +0100, Roberto Sassu wrote:
> This patch renames active_banks (member of tpm_chip) to allocated_banks,
> stores the number of allocated PCR banks in nr_allocated_banks (new member
> of tpm_chip), and replaces the static array with a pointer to a dynamically
> allocated array.
> 
> tpm2_get_pcr_allocation() determines if a PCR bank is allocated by checking
> the mask in the TPML_PCR_SELECTION structure returned by the TPM for
> TPM2_Get_Capability(). If a bank is not allocated, the TPM returns that
> bank in TPML_PCR_SELECTION, with all bits in the mask set to zero. In this
> case, the bank is not included in chip->allocated_banks, to avoid that TPM
> driver users unnecessarily calculate a digest for that bank.
> 
> One PCR bank with algorithm set to SHA1 is always allocated for TPM 1.x.
> 
> As a consequence of the introduction of nr_allocated_banks,
> tpm_pcr_extend() does not check anymore if the algorithm stored in tpm_chip
> is equal to zero.
> 
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> ---
>  drivers/char/tpm/tpm-chip.c      |  1 +
>  drivers/char/tpm/tpm-interface.c | 18 +++++++++--------
>  drivers/char/tpm/tpm.h           |  3 ++-
>  drivers/char/tpm/tpm1-cmd.c      | 10 ++++++++++
>  drivers/char/tpm/tpm2-cmd.c      | 34 ++++++++++++++++++++++----------
>  5 files changed, 47 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 32db84683c40..ce851c62bb68 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->allocated_banks);
>  	kfree(chip);
>  }
>  
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index d9439f9abe78..7b80919228be 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -488,8 +488,7 @@ EXPORT_SYMBOL_GPL(tpm_pcr_read);
>  int tpm_pcr_extend(struct tpm_chip *chip, u32 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);
> @@ -497,16 +496,19 @@ int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash)
>  		return -ENODEV;
>  
>  	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> -		memset(digest_list, 0, sizeof(digest_list));
> +		digest_list = kcalloc(chip->nr_allocated_banks,
> +				      sizeof(*digest_list), GFP_KERNEL);
> +		if (!digest_list)
> +			return -ENOMEM;

You could preallocate digest list and place it to struct tpm_chip
instead of doing it everytime tpm_pcr_extend() called.

>  
> -		for (i = 0; i < ARRAY_SIZE(chip->active_banks) &&
> -			    chip->active_banks[i] != TPM2_ALG_ERROR; i++) {
> -			digest_list[i].alg_id = chip->active_banks[i];
> +		for (i = 0; i < chip->nr_allocated_banks; i++) {
> +			digest_list[i].alg_id = chip->allocated_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_allocated_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 f27d1f38a93d..6b94306ab7c5 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -257,7 +257,8 @@ struct tpm_chip {
>  	const struct attribute_group *groups[3];
>  	unsigned int groups_cnt;
>  
> -	u16 active_banks[7];
> +	u32 nr_allocated_banks;
> +	u16 *allocated_banks;
>  #ifdef CONFIG_ACPI
>  	acpi_handle acpi_dev_handle;
>  	char ppi_version[TPM_PPI_VERSION_LEN + 1];
> diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
> index 6f306338953b..0874743ca96d 100644
> --- a/drivers/char/tpm/tpm1-cmd.c
> +++ b/drivers/char/tpm/tpm1-cmd.c
> @@ -709,6 +709,16 @@ int tpm1_auto_startup(struct tpm_chip *chip)
>  		goto out;
>  	}
>  
> +	chip->allocated_banks = kcalloc(1, sizeof(*chip->allocated_banks),
> +					GFP_KERNEL);
> +	if (!chip->allocated_banks) {
> +		rc = -ENOMEM;
> +		goto out;
> +	}
> +
> +	chip->allocated_banks[0] = TPM2_ALG_SHA1;
> +	chip->nr_allocated_banks = 1;
> +
>  	return rc;
>  out:
>  	if (rc > 0)
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index a6bec13afa69..245669a7aba5 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -234,7 +234,7 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, u32 count,
>  	int i;
>  	int j;
>  
> -	if (count > ARRAY_SIZE(chip->active_banks))
> +	if (count > chip->nr_allocated_banks)
>  		return -EINVAL;
>  
>  	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
> @@ -825,11 +825,14 @@ 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 nr_possible_banks;
> +	u32 nr_alloc_banks = 0;
> +	u16 hash_alg;
>  	u32 rsp_len;
>  	int rc;
>  	int i = 0;
> +	int j;
>  
>  	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
>  	if (rc)
> @@ -844,11 +847,14 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>  	if (rc)
>  		goto out;
>  
> -	count = be32_to_cpup(
> +	nr_possible_banks = be32_to_cpup(
>  		(__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
>  
> -	if (count > ARRAY_SIZE(chip->active_banks)) {
> -		rc = -ENODEV;
> +	chip->allocated_banks = kcalloc(nr_possible_banks,
> +					sizeof(*chip->allocated_banks),
> +					GFP_KERNEL);
> +	if (!chip->allocated_banks) {
> +		rc = -ENOMEM;
>  		goto out;
>  	}
>  
> @@ -857,7 +863,7 @@ 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 < nr_possible_banks; i++) {
>  		pcr_select_offset = marker +
>  			offsetof(struct tpm2_pcr_selection, size_of_select);
>  		if (pcr_select_offset >= end) {
> @@ -866,17 +872,25 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>  		}
>  
>  		memcpy(&pcr_selection, marker, sizeof(pcr_selection));
> -		chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
> +		hash_alg = be16_to_cpu(pcr_selection.hash_alg);
> +
> +		for (j = 0; j < pcr_selection.size_of_select; j++)
> +			if (pcr_selection.pcr_select[j])
> +				break;
> +
> +		if (j < pcr_selection.size_of_select) {
> +			chip->allocated_banks[nr_alloc_banks] = hash_alg;
> +			nr_alloc_banks++;
> +		}

The same comment as before: you should use memchr_inv() here.

> +
>  		sizeof_pcr_selection = sizeof(pcr_selection.hash_alg) +
>  			sizeof(pcr_selection.size_of_select) +
>  			pcr_selection.size_of_select;
>  		marker = marker + sizeof_pcr_selection;
>  	}
>  
> +	chip->nr_allocated_banks = nr_alloc_banks;
>  out:
> -	if (i < ARRAY_SIZE(chip->active_banks))
> -		chip->active_banks[i] = TPM2_ALG_ERROR;
> -
>  	tpm_buf_destroy(&buf);
>  
>  	return rc;
> -- 
> 2.17.1
> 

/Jarkko