Re: [PATCH] tpm: Define TPM2_SPACE_BUFFER_SIZE to replace the use of PAGE_SIZE

[Jerry Snitselaar <jsnitsel@xxxxxxxxxx>]

On Fri Jul 03 20, Jarkko Sakkinen wrote:
> The size of the buffers for storing context's and sessions can vary from
> arch to arch as PAGE_SIZE can be anything between 4 kB and 256 kB (the
> maximum for PPC64). Define a fixed buffer size set to 16 kB. This should be
> enough for most use with three handles (that is how many we allow at the
> moment). Parametrize the buffer size while doing this, so that it is easier
> to revisit this later on if required.
>
> Reported-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 745b361e989a ("tpm: infrastructure for TPM spaces")
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>

Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>

> ---
> v2: Also use the new buffer size for chip->work_buffer (reported by stefanb)
> drivers/char/tpm/tpm-chip.c   |  9 ++-------
> drivers/char/tpm/tpm.h        |  5 ++++-
> drivers/char/tpm/tpm2-space.c | 26 ++++++++++++++++----------
> drivers/char/tpm/tpmrm-dev.c  |  2 +-
> include/linux/tpm.h           |  5 +++--
> 5 files changed, 26 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 8c77e88012e9..ddaeceb7e109 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -386,13 +386,8 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> 	chip->cdev.owner = THIS_MODULE;
> 	chip->cdevs.owner = THIS_MODULE;
>
> -	chip->work_space.context_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> -	if (!chip->work_space.context_buf) {
> -		rc = -ENOMEM;
> -		goto out;
> -	}
> -	chip->work_space.session_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> -	if (!chip->work_space.session_buf) {
> +	rc = tpm2_init_space(&chip->work_space, TPM2_SPACE_BUFFER_SIZE);
> +	if (rc) {
> 		rc = -ENOMEM;
> 		goto out;
> 	}
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 0fbcede241ea..947d1db0a5cc 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -59,6 +59,9 @@ enum tpm_addr {
>
> #define TPM_TAG_RQU_COMMAND 193
>
> +/* TPM2 specific constants. */
> +#define TPM2_SPACE_BUFFER_SIZE		16384 /* 16 kB */
> +
> struct	stclear_flags_t {
> 	__be16	tag;
> 	u8	deactivated;
> @@ -228,7 +231,7 @@ unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal);
> int tpm2_probe(struct tpm_chip *chip);
> int tpm2_get_cc_attrs_tbl(struct tpm_chip *chip);
> int tpm2_find_cc(struct tpm_chip *chip, u32 cc);
> -int tpm2_init_space(struct tpm_space *space);
> +int tpm2_init_space(struct tpm_space *space, unsigned int buf_size);
> void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space);
> void tpm2_flush_space(struct tpm_chip *chip);
> int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
> diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> index 982d341d8837..784b8b3cb903 100644
> --- a/drivers/char/tpm/tpm2-space.c
> +++ b/drivers/char/tpm/tpm2-space.c
> @@ -38,18 +38,21 @@ static void tpm2_flush_sessions(struct tpm_chip *chip, struct tpm_space *space)
> 	}
> }
>
> -int tpm2_init_space(struct tpm_space *space)
> +int tpm2_init_space(struct tpm_space *space, unsigned int buf_size)
> {
> -	space->context_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> +	space->context_buf = kzalloc(buf_size, GFP_KERNEL);
> 	if (!space->context_buf)
> 		return -ENOMEM;
>
> -	space->session_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> +	space->session_buf = kzalloc(buf_size, GFP_KERNEL);
> 	if (space->session_buf == NULL) {
> 		kfree(space->context_buf);
> +		/* Prevent caller getting a dangling pointer. */
> +		space->context_buf = NULL;
> 		return -ENOMEM;
> 	}
>
> +	space->buf_size = buf_size;
> 	return 0;
> }
>
> @@ -311,8 +314,10 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd,
> 	       sizeof(space->context_tbl));
> 	memcpy(&chip->work_space.session_tbl, &space->session_tbl,
> 	       sizeof(space->session_tbl));
> -	memcpy(chip->work_space.context_buf, space->context_buf, PAGE_SIZE);
> -	memcpy(chip->work_space.session_buf, space->session_buf, PAGE_SIZE);
> +	memcpy(chip->work_space.context_buf, space->context_buf,
> +	       space->buf_size);
> +	memcpy(chip->work_space.session_buf, space->session_buf,
> +	       space->buf_size);
>
> 	rc = tpm2_load_space(chip);
> 	if (rc) {
> @@ -492,7 +497,7 @@ static int tpm2_save_space(struct tpm_chip *chip)
> 			continue;
>
> 		rc = tpm2_save_context(chip, space->context_tbl[i],
> -				       space->context_buf, PAGE_SIZE,
> +				       space->context_buf, space->buf_size,
> 				       &offset);
> 		if (rc == -ENOENT) {
> 			space->context_tbl[i] = 0;
> @@ -509,9 +514,8 @@ static int tpm2_save_space(struct tpm_chip *chip)
> 			continue;
>
> 		rc = tpm2_save_context(chip, space->session_tbl[i],
> -				       space->session_buf, PAGE_SIZE,
> +				       space->session_buf, space->buf_size,
> 				       &offset);
> -
> 		if (rc == -ENOENT) {
> 			/* handle error saving session, just forget it */
> 			space->session_tbl[i] = 0;
> @@ -557,8 +561,10 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
> 	       sizeof(space->context_tbl));
> 	memcpy(&space->session_tbl, &chip->work_space.session_tbl,
> 	       sizeof(space->session_tbl));
> -	memcpy(space->context_buf, chip->work_space.context_buf, PAGE_SIZE);
> -	memcpy(space->session_buf, chip->work_space.session_buf, PAGE_SIZE);
> +	memcpy(space->context_buf, chip->work_space.context_buf,
> +	       space->buf_size);
> +	memcpy(space->session_buf, chip->work_space.session_buf,
> +	       space->buf_size);
>
> 	return 0;
> out:
> diff --git a/drivers/char/tpm/tpmrm-dev.c b/drivers/char/tpm/tpmrm-dev.c
> index 7a0a7051a06f..eef0fb06ea83 100644
> --- a/drivers/char/tpm/tpmrm-dev.c
> +++ b/drivers/char/tpm/tpmrm-dev.c
> @@ -21,7 +21,7 @@ static int tpmrm_open(struct inode *inode, struct file *file)
> 	if (priv == NULL)
> 		return -ENOMEM;
>
> -	rc = tpm2_init_space(&priv->space);
> +	rc = tpm2_init_space(&priv->space, TPM2_SPACE_BUFFER_SIZE);
> 	if (rc) {
> 		kfree(priv);
> 		return -ENOMEM;
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 03e9b184411b..d501156fedda 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -93,9 +93,10 @@ enum tpm_duration {
>
> struct tpm_space {
> 	u32 context_tbl[3];
> -	u8 *context_buf;
> +	u8  *context_buf;
> 	u32 session_tbl[3];
> -	u8 *session_buf;
> +	u8  *session_buf;
> +	u32 buf_size;
> };
>
> struct tpm_bios_log {
> --
> 2.25.1