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Date: Thu, 25 Jun 2020 08:13:09 -0400
From: Stefan Berger <stefanb@...ux.ibm.com>
To: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
linux-integrity@...r.kernel.org
Cc: James Bottomley <James.Bottomley@...senPartnership.com>,
Peter Huewe <peterhuewe@....de>,
Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jerry Snitselaar <jsnitsel@...hat.com>,
Sumit Garg <sumit.garg@...aro.org>,
Alexey Klimov <aklimov@...hat.com>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: tpm2-space: Resize session and context buffers
dynamically
On 6/25/20 12:24 AM, Jarkko Sakkinen wrote:
> Re-allocate context and session buffers when needed. Scale them in page
> increments so that the reallocation is only seldomly required, and thus
> causes minimal stress to the system. Add a static maximum limit of four
> pages for buffer sizes.
>
> Cc: James Bottomley <James.Bottomley@...senPartnership.com>
> Suggested-by: Stefan Berger <stefanb@...ux.ibm.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> ---
> Tested only for compilation.
> drivers/char/tpm/tpm2-space.c | 80 ++++++++++++++++++++++++-----------
> include/linux/tpm.h | 6 ++-
> 2 files changed, 59 insertions(+), 27 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> index 982d341d8837..acb9e82bf9e8 100644
> --- a/drivers/char/tpm/tpm2-space.c
> +++ b/drivers/char/tpm/tpm2-space.c
> @@ -15,6 +15,8 @@
> #include <asm/unaligned.h>
> #include "tpm.h"
>
> +#define TPM2_SPACE_MAX_BUFFER_SIZE (4 * PAGE_SIZE)
PAGE_SIZE is 64k on ppc64. Rather use 4 * 4096?
Rest looks good.
> +
> enum tpm2_handle_types {
> TPM2_HT_HMAC_SESSION = 0x02000000,
> TPM2_HT_POLICY_SESSION = 0x03000000,
> @@ -47,9 +49,12 @@ int tpm2_init_space(struct tpm_space *space)
> space->session_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> if (space->session_buf == NULL) {
> kfree(space->context_buf);
> + space->context_buf = NULL;
> return -ENOMEM;
> }
>
> + space->context_size = PAGE_SIZE;
> + space->session_size = PAGE_SIZE;
> return 0;
> }
>
> @@ -116,11 +121,13 @@ static int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
> return 0;
> }
>
> -static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
> - unsigned int buf_size, unsigned int *offset)
> +static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 **buf,
> + unsigned int *buf_size, unsigned int *offset)
> {
> - struct tpm_buf tbuf;
> + unsigned int new_buf_size;
> unsigned int body_size;
> + struct tpm_buf tbuf;
> + void *new_buf;
> int rc;
>
> rc = tpm_buf_init(&tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_SAVE);
> @@ -131,31 +138,48 @@ static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
>
> rc = tpm_transmit_cmd(chip, &tbuf, 0, NULL);
> if (rc < 0) {
> - dev_warn(&chip->dev, "%s: failed with a system error %d\n",
> - __func__, rc);
> - tpm_buf_destroy(&tbuf);
> - return -EFAULT;
> + rc = -EFAULT;
> + goto err;
> } else if (tpm2_rc_value(rc) == TPM2_RC_REFERENCE_H0) {
> - tpm_buf_destroy(&tbuf);
> - return -ENOENT;
> + rc = -ENOENT;
> + goto out;
> } else if (rc) {
> - dev_warn(&chip->dev, "%s: failed with a TPM error 0x%04X\n",
> - __func__, rc);
> - tpm_buf_destroy(&tbuf);
> - return -EFAULT;
> + rc = -EFAULT;
> + goto err;
> }
>
> body_size = tpm_buf_length(&tbuf) - TPM_HEADER_SIZE;
> - if ((*offset + body_size) > buf_size) {
> - dev_warn(&chip->dev, "%s: out of backing storage\n", __func__);
> - tpm_buf_destroy(&tbuf);
> - return -ENOMEM;
> + /* We grow the buffer in page increments. */
> + new_buf_size = PFN_UP(*offset + body_size);
> +
> + if (new_buf_size > TPM2_SPACE_MAX_BUFFER_SIZE) {
> + rc = -ENOMEM;
> + goto err;
> }
>
> - memcpy(&buf[*offset], &tbuf.data[TPM_HEADER_SIZE], body_size);
> + if (new_buf_size > *buf_size) {
> + new_buf = krealloc(*buf, new_buf_size, GFP_KERNEL);
> + if (!new_buf) {
> + rc = -ENOMEM;
> + goto err;
> + }
> +
> + *buf = new_buf;
> + *buf_size = new_buf_size;
> + }
> +
> + memcpy(*buf + *offset, &tbuf.data[TPM_HEADER_SIZE], body_size);
> *offset += body_size;
> +
> +out:
> tpm_buf_destroy(&tbuf);
> - return 0;
> + return rc;
> +
> +err:
> + dev_warn(&chip->dev, "%s: ret=%d\n", __func__, rc);
> +
> + tpm_buf_destroy(&tbuf);
> + return rc;
> }
>
> void tpm2_flush_space(struct tpm_chip *chip)
> @@ -311,8 +335,10 @@ 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->context_size);
> + memcpy(chip->work_space.session_buf, space->session_buf,
> + space->session_size);
>
> rc = tpm2_load_space(chip);
> if (rc) {
> @@ -492,7 +518,8 @@ 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->context_size,
> &offset);
> if (rc == -ENOENT) {
> space->context_tbl[i] = 0;
> @@ -509,7 +536,8 @@ 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->session_size,
> &offset);
>
> if (rc == -ENOENT) {
> @@ -557,8 +585,10 @@ 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->context_size);
> + memcpy(space->session_buf, chip->work_space.session_buf,
> + space->session_size);
>
> return 0;
> out:
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 03e9b184411b..9ea39e8f7162 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -92,10 +92,12 @@ enum tpm_duration {
> #define TPM_PPI_VERSION_LEN 3
>
> struct tpm_space {
> + u8 *context_buf;
> + u8 *session_buf;
> + u32 context_size;
> + u32 session_size;
> u32 context_tbl[3];
> - u8 *context_buf;
> u32 session_tbl[3];
> - u8 *session_buf;
> };
>
> struct tpm_bios_log {
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