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Subject: Re: [PATCH v4 4/4] tpm: migrate tpm2_get_random() to use struct
 tpm_buf
To:     Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        linux-integrity@vger.kernel.org
Cc:     linux-security-module@vger.kernel.org,
        Peter Huewe <peterhuewe@gmx.de>,
        Jason Gunthorpe <jgg@ziepe.ca>, Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        open list <linux-kernel@vger.kernel.org>
References: <20180326121406.14548-1-jarkko.sakkinen@linux.intel.com>
 <20180326121406.14548-5-jarkko.sakkinen@linux.intel.com>
From:   Nayna Jain <nayna@linux.vnet.ibm.com>
Date:   Fri, 18 May 2018 11:39:16 +0530
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On 03/26/2018 05:44 PM, Jarkko Sakkinen wrote:
> In order to make struct tpm_buf the first class object for constructing
> TPM commands, migrate tpm2_get_random() to use it. In addition, removed
> remaining references to struct tpm2_cmd. All of them use it to acquire
> the length of the response, which can be achieved by using
> tpm_buf_length().
>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> ---
>   drivers/char/tpm/tpm.h      | 19 ++++-----
>   drivers/char/tpm/tpm2-cmd.c | 98 ++++++++++++++++++---------------------------
>   2 files changed, 49 insertions(+), 68 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 7f2d0f489e9c..aa849a1b2641 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -421,23 +421,24 @@ struct tpm_buf {
>   	u8 *data;
>   };
>
> -static inline int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
> +static inline void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
>   {
>   	struct tpm_input_header *head;
> +	head = (struct tpm_input_header *)buf->data;
> +	head->tag = cpu_to_be16(tag);
> +	head->length = cpu_to_be32(sizeof(*head));
> +	head->ordinal = cpu_to_be32(ordinal);
> +}
>
> +static inline int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
> +{
>   	buf->data_page = alloc_page(GFP_HIGHUSER);
>   	if (!buf->data_page)
>   		return -ENOMEM;
>
>   	buf->flags = 0;
>   	buf->data = kmap(buf->data_page);
> -
> -	head = (struct tpm_input_header *) buf->data;
> -
> -	head->tag = cpu_to_be16(tag);
> -	head->length = cpu_to_be32(sizeof(*head));
> -	head->ordinal = cpu_to_be32(ordinal);
> -
> +	tpm_buf_reset(buf, tag, ordinal);
>   	return 0;
>   }
>
> @@ -566,7 +567,7 @@ static inline u32 tpm2_rc_value(u32 rc)
>   int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf);
>   int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
>   		    struct tpm2_digest *digests);
> -int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max);
> +int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
>   void tpm2_flush_context_cmd(struct tpm_chip *chip, u32 handle,
>   			    unsigned int flags);
>   int tpm2_seal_trusted(struct tpm_chip *chip,
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index b3b52f9eb65f..d5c222f98515 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -27,25 +27,6 @@ enum tpm2_session_attributes {
>   	TPM2_SA_CONTINUE_SESSION	= BIT(0),
>   };
>
> -struct tpm2_get_random_in {
> -	__be16	size;
> -} __packed;
> -
> -struct tpm2_get_random_out {
> -	__be16	size;
> -	u8	buffer[TPM_MAX_RNG_DATA];
> -} __packed;
> -
> -union tpm2_cmd_params {
> -	struct	tpm2_get_random_in	getrandom_in;
> -	struct	tpm2_get_random_out	getrandom_out;
> -};
> -
> -struct tpm2_cmd {
> -	tpm_cmd_header		header;
> -	union tpm2_cmd_params	params;
> -} __packed;
> -
>   struct tpm2_hash {
>   	unsigned int crypto_id;
>   	unsigned int tpm_id;
> @@ -300,67 +281,70 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
>   }
>
>
> -#define TPM2_GETRANDOM_IN_SIZE \
> -	(sizeof(struct tpm_input_header) + \
> -	 sizeof(struct tpm2_get_random_in))
> -
> -static const struct tpm_input_header tpm2_getrandom_header = {
> -	.tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
> -	.length = cpu_to_be32(TPM2_GETRANDOM_IN_SIZE),
> -	.ordinal = cpu_to_be32(TPM2_CC_GET_RANDOM)
> -};
> +struct tpm2_get_random_out {
> +	__be16 size;
> +	u8 buffer[TPM_MAX_RNG_DATA];
> +} __packed;
>
>   /**
>    * tpm2_get_random() - get random bytes from the TPM RNG
>    *
>    * @chip: TPM chip to use
> - * @out: destination buffer for the random bytes
> + * @dest: destination buffer for the random bytes
>    * @max: the max number of bytes to write to @out
>    *
>    * Return:
> - *    Size of the output buffer, or -EIO on error.
> + * size of the output buffer when the operation is successful.
> + * A negative number for system errors (errno).
>    */
> -int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max)
> +int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>   {
> -	struct tpm2_cmd cmd;
> -	u32 recd, rlength;
> -	u32 num_bytes;
> +	struct tpm2_get_random_out *out;
> +	struct tpm_buf buf;
> +	u32 recd;
> +	u32 num_bytes = max;
>   	int err;
>   	int total = 0;
>   	int retries = 5;
> -	u8 *dest = out;
> -
> -	num_bytes = min_t(u32, max, sizeof(cmd.params.getrandom_out.buffer));
> +	u8 *dest_ptr = dest;
>
> -	if (!out || !num_bytes ||
> -	    max > sizeof(cmd.params.getrandom_out.buffer))
> +	if (!num_bytes || max > TPM_MAX_RNG_DATA)
>   		return -EINVAL;
>
> -	do {
> -		cmd.header.in = tpm2_getrandom_header;
> -		cmd.params.getrandom_in.size = cpu_to_be16(num_bytes);
> +	err = tpm_buf_init(&buf, 0, 0);
> +	if (err)
> +		return err;
>
> -		err = tpm_transmit_cmd(chip, NULL, &cmd, sizeof(cmd),
> +	do {
> +		tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_RANDOM);
> +		tpm_buf_append_u16(&buf, num_bytes);
> +		err = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE,
>   				       offsetof(struct tpm2_get_random_out,
>   						buffer),
>   				       0, "attempting get random");
>   		if (err)
> -			break;
> +			goto out;
>
> -		recd = min_t(u32, be16_to_cpu(cmd.params.getrandom_out.size),
> -			     num_bytes);
> -		rlength = be32_to_cpu(cmd.header.out.length);
> -		if (rlength < offsetof(struct tpm2_get_random_out, buffer) +
> -			      recd)
> -			return -EFAULT;
> -		memcpy(dest, cmd.params.getrandom_out.buffer, recd);
> +		out = (struct tpm2_get_random_out *)
> +			&buf.data[TPM_HEADER_SIZE];
> +		recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
> +		if (tpm_buf_length(&buf) <
> +		    offsetof(struct tpm2_get_random_out, buffer) + recd) {
> +			err = -EFAULT;
> +			goto out;
> +		}
> +		memcpy(dest_ptr, out->buffer, recd);
>
> -		dest += recd;
> +		dest_ptr += recd;
>   		total += recd;
>   		num_bytes -= recd;
>   	} while (retries-- && total < max);
>
> +	tpm_buf_destroy(&buf);
>   	return total ? total : -EIO;
> +out:
> +	tpm_buf_destroy(&buf);
> +	return err;
>   }

How about having it as :

     if (!total)
         err = -EIO;
out:
     tpm_buf_destroy(&buf);
     return total?:err;

>   /**
> @@ -434,7 +418,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>   {
>   	unsigned int blob_len;
>   	struct tpm_buf buf;
> -	u32 hash, rlength;
> +	u32 hash;
>   	int i;
>   	int rc;
>
> @@ -509,8 +493,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>   		rc = -E2BIG;
>   		goto out;
>   	}
> -	rlength = be32_to_cpu(((struct tpm2_cmd *)&buf)->header.out.length);
> -	if (rlength < TPM_HEADER_SIZE + 4 + blob_len) {
> +	if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 4 + blob_len) {
>   		rc = -EFAULT;
>   		goto out;
>   	}
> @@ -620,7 +603,6 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>   	u16 data_len;
>   	u8 *data;
>   	int rc;
> -	u32 rlength;
>
>   	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
>   	if (rc)
> @@ -648,9 +630,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>   			goto out;
>   		}
>
> -		rlength = be32_to_cpu(((struct tpm2_cmd *)&buf)
> -					->header.out.length);
> -		if (rlength < TPM_HEADER_SIZE + 6 + data_len) {
> +		if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 6 + data_len) {
>   			rc = -EFAULT;
>   			goto out;
>   		}
Probably, all the changes related to the use of tpm_buf_length() could 
be a separate patch in itself ?

Otherwise,

Tested-by: Nayna Jain<nayna@linux.vnet.ibm.com>

Thanks & Regards,
    - Nayna