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Message-ID: <20200625212817.rxzjsgecrfpcb6ph@cantor>
Date: Thu, 25 Jun 2020 14:28:17 -0700
From: Jerry Snitselaar <jsnitsel@...hat.com>
To: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Cc: linux-integrity@...r.kernel.org,
James Bottomley <James.Bottomley@...senpartnership.com>,
Stefan Berger <stefanb@...ux.ibm.com>,
Peter Huewe <peterhuewe@....de>,
Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Sumit Garg <sumit.garg@...aro.org>,
Alexey Klimov <aklimov@...hat.com>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] tpm: tpm2-space: Resize session and context buffers
dynamically
On Thu Jun 25 20, 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.
>v2: TPM2_SPACE_DEFAULT_BUFFER_SIZE
> drivers/char/tpm/tpm2-space.c | 87 ++++++++++++++++++++++++-----------
> include/linux/tpm.h | 6 ++-
> 2 files changed, 64 insertions(+), 29 deletions(-)
>
>diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
>index 982d341d8837..b8ece01d6afb 100644
>--- a/drivers/char/tpm/tpm2-space.c
>+++ b/drivers/char/tpm/tpm2-space.c
>@@ -15,6 +15,9 @@
> #include <asm/unaligned.h>
> #include "tpm.h"
>
>+#define TPM2_SPACE_DEFAULT_BUFFER_SIZE PAGE_SIZE
>+#define TPM2_SPACE_MAX_BUFFER_SIZE (4 * PAGE_SIZE)
>+
> enum tpm2_handle_types {
> TPM2_HT_HMAC_SESSION = 0x02000000,
> TPM2_HT_POLICY_SESSION = 0x03000000,
>@@ -40,16 +43,21 @@ static void tpm2_flush_sessions(struct tpm_chip *chip, struct tpm_space *space)
>
> int tpm2_init_space(struct tpm_space *space)
> {
>- space->context_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
>+ space->context_buf = kzalloc(TPM2_SPACE_DEFAULT_BUFFER_SIZE,
>+ GFP_KERNEL);
> if (!space->context_buf)
> return -ENOMEM;
>
>- space->session_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
>+ space->session_buf = kzalloc(TPM2_SPACE_DEFAULT_BUFFER_SIZE,
>+ GFP_KERNEL);
> if (space->session_buf == NULL) {
> kfree(space->context_buf);
>+ space->context_buf = NULL;
> return -ENOMEM;
> }
>
>+ space->context_size = TPM2_SPACE_DEFAULT_BUFFER_SIZE;
>+ space->session_size = TPM2_SPACE_DEFAULT_BUFFER_SIZE;
> return 0;
> }
>
>@@ -116,11 +124,13 @@ 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 +141,48 @@ 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;
> }
>
Would it be worthwhile to still output something here since it is changing
the value of rc returned from tpm_transmit_cmd()? Wondering if it would
be useful for debugging to know what the returned error was. Other than
that question looks good to me pending what is decided on using PAGE_SIZE.
Regards,
Jerry
> 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 +338,10 @@ 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 +521,8 @@ 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 +539,8 @@ 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 +588,10 @@ 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 {
>--
>2.25.1
>
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