Re: [PATCH v4 4/4] tpm: migrate tpm2_get_random() to use struct tpm_buf

Nayna Jain
2018-05-18T06:09:16Z

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