Re: [PATCH v2 7/7] tpm2: add session handle context saving and restoring to the space code

From: Jarkko Sakkinen
Date: Thu Feb 23 2017 - 04:04:47 EST

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On Thu, Feb 16, 2017 at 09:25:20PM +0200, Jarkko Sakkinen wrote:
> From: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
>
> Sessions are different from transient objects in that their handles
> may not be virtualized (because they're used for some hmac
> calculations). Additionally when a session is context saved, a
> vestigial memory remains in the TPM and if it is also flushed, that
> will be lost and the session context will refuse to load next time, so
> the code is updated to flush only transient objects after a context
> save. Add a separate array (chip->session_tbl) to save and restore
> sessions by handle. Use the failure of a context save or load to
> signal that the session has been flushed from the TPM and we can
> remove its memory from chip->session_tbl.
>
> Sessions are also isolated during each instance of a tpm space. This
> means that spaces shouldn't be able to see each other's sessions and
> is enforced by ensuring that a space user may only refer to sessions
> handles that are present in their own chip->session_tbl. Finally when
> a space is closed, all the sessions belonging to it should be flushed
> so the handles may be re-used by other spaces.
>
> Note that if we get a session save or load error, all sessions are
> effectively flushed. Even though we restore the session buffer, all
> the old sessions will refuse to load after the flush and they'll be
> purged from our session memory. This means that while transient
> context handling is still soft in the face of errors, session handling
> is hard (any failure of the model means all sessions are lost).
>
> Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>

Reviewed-by: Jarkko Sakkinen <jarkko.sakkine@xxxxxxxxxxxxxxx>

I'll give Tested-by separately once I've updated tpm2_smoke.py

/Jarkko

> ---
> drivers/char/tpm/tpm-chip.c | 6 +++
> drivers/char/tpm/tpm.h | 4 +-
> drivers/char/tpm/tpm2-space.c | 105 +++++++++++++++++++++++++++++++++++++++++-
> drivers/char/tpm/tpms-dev.c | 2 +-
> 4 files changed, 113 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index c71c353..e8536ab 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -130,6 +130,7 @@ static void tpm_dev_release(struct device *dev)
>
> kfree(chip->log.bios_event_log);
> kfree(chip->work_space.context_buf);
> + kfree(chip->work_space.session_buf);
> kfree(chip);
> }
>
> @@ -224,6 +225,11 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> rc = -ENOMEM;
> goto out;
> }
> + chip->work_space.session_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> + if (!chip->work_space.session_buf) {
> + rc = -ENOMEM;
> + goto out;
> + }
>
> return chip;
>
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 822ca67..ffee8b5 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -161,6 +161,8 @@ enum tpm2_cc_attrs {
> struct tpm_space {
> u32 context_tbl[3];
> u8 *context_buf;
> + u32 session_tbl[3];
> + u8 *session_buf;
> };
>
> enum tpm_chip_flags {
> @@ -589,7 +591,7 @@ int tpm2_probe(struct tpm_chip *chip);
> ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip);
> int tpm2_find_cc(struct tpm_chip *chip, u32 cc);
> int tpm2_init_space(struct tpm_space *space);
> -void tpm2_del_space(struct tpm_space *space);
> +void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space);
> int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u32 cc,
> u8 *cmd);
> int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
> diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> index e955548..d36d81e 100644
> --- a/drivers/char/tpm/tpm2-space.c
> +++ b/drivers/char/tpm/tpm2-space.c
> @@ -32,18 +32,39 @@ struct tpm2_context {
> __be16 blob_size;
> } __packed;
>
> +static void tpm2_flush_sessions(struct tpm_chip *chip, struct tpm_space *space)
> +{
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(space->session_tbl); i++) {
> + if (space->session_tbl[i])
> + tpm2_flush_context_cmd(chip, space->session_tbl[i],
> + TPM_TRANSMIT_UNLOCKED);
> + }
> +}
> +
> int tpm2_init_space(struct tpm_space *space)
> {
> space->context_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> if (!space->context_buf)
> return -ENOMEM;
>
> + space->session_buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
> + if (space->session_buf == NULL) {
> + kfree(space->context_buf);
> + return -ENOMEM;
> + }
> +
> return 0;
> }
>
> -void tpm2_del_space(struct tpm_space *space)
> +void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space)
> {
> + mutex_lock(&chip->tpm_mutex);
> + tpm2_flush_sessions(chip, space);
> + mutex_unlock(&chip->tpm_mutex);
> kfree(space->context_buf);
> + kfree(space->session_buf);
> }
>
> static int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
> @@ -69,6 +90,20 @@ static int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
> __func__, rc);
> tpm_buf_destroy(&tbuf);
> return -EFAULT;
> + } else if (tpm2_rc_value(rc) == TPM2_RC_HANDLE ||
> + rc == TPM2_RC_REFERENCE_H0) {
> + /*
> + * TPM_RC_HANDLE means that the session context can't
> + * be loaded because of an internal counter mismatch
> + * that makes the TPM think there might have been a
> + * replay. This might happen if the context was saved
> + * and loaded outside the space.
> + *
> + * TPM_RC_REFERENCE_H0 means the session has been
> + * flushed outside the space
> + */
> + rc = -ENOENT;
> + tpm_buf_destroy(&tbuf);
> } else if (rc > 0) {
> dev_warn(&chip->dev, "%s: failed with a TPM error 0x%04X\n",
> __func__, rc);
> @@ -121,7 +156,6 @@ static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
> }
>
> memcpy(&buf[*offset], &tbuf.data[TPM_HEADER_SIZE], body_size);
> - tpm2_flush_context_cmd(chip, handle, TPM_TRANSMIT_UNLOCKED);
> *offset += body_size;
> tpm_buf_destroy(&tbuf);
> return 0;
> @@ -136,6 +170,8 @@ static void tpm2_flush_space(struct tpm_chip *chip)
> if (space->context_tbl[i] && ~space->context_tbl[i])
> tpm2_flush_context_cmd(chip, space->context_tbl[i],
> TPM_TRANSMIT_UNLOCKED);
> +
> + tpm2_flush_sessions(chip, space);
> }
>
> static int tpm2_load_space(struct tpm_chip *chip)
> @@ -161,6 +197,28 @@ static int tpm2_load_space(struct tpm_chip *chip)
> return rc;
> }
>
> + for (i = 0, offset = 0; i < ARRAY_SIZE(space->session_tbl); i++) {
> + u32 handle;
> +
> + if (!space->session_tbl[i])
> + continue;
> +
> + rc = tpm2_load_context(chip, space->session_buf,
> + &offset, &handle);
> + if (rc == -ENOENT) {
> + /* load failed, just forget session */
> + space->session_tbl[i] = 0;
> + } else if (rc) {
> + tpm2_flush_space(chip);
> + return rc;
> + }
> + if (handle != space->session_tbl[i]) {
> + dev_warn(&chip->dev, "session restored to wrong handle\n");
> + tpm2_flush_space(chip);
> + return -EFAULT;
> + }
> + }
> +
> return 0;
> }
>
> @@ -215,7 +273,10 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u32 cc,
>
> memcpy(&chip->work_space.context_tbl, &space->context_tbl,
> 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);
>
> rc = tpm2_load_space(chip);
> if (rc) {
> @@ -232,6 +293,22 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u32 cc,
> return 0;
> }
>
> +static bool tpm2_add_session(struct tpm_chip *chip, u32 handle)
> +{
> + struct tpm_space *space = &chip->work_space;
> + int i;
> +
> + for (i = 0; i < ARRAY_SIZE(space->session_tbl); i++)
> + if (space->session_tbl[i] == 0)
> + break;
> +
> + if (i == ARRAY_SIZE(space->session_tbl))
> + return false;
> +
> + space->session_tbl[i] = handle;
> + return true;
> +}
> +
> static u32 tpm2_map_to_vhandle(struct tpm_space *space, u32 phandle, bool alloc)
> {
> int i;
> @@ -288,6 +365,8 @@ static int tpm2_map_response_header(struct tpm_chip *chip, u32 cc, u8 *rsp,
> break;
> case TPM2_HT_HMAC_SESSION:
> case TPM2_HT_POLICY_SESSION:
> + if (!tpm2_add_session(chip, phandle))
> + goto out_no_slots;
> break;
> default:
> dev_err(&chip->dev, "%s: unknown handle 0x%08X\n",
> @@ -388,9 +467,28 @@ static int tpm2_save_space(struct tpm_chip *chip)
> } else if (rc)
> return rc;
>
> + tpm2_flush_context_cmd(chip, space->context_tbl[i],
> + TPM_TRANSMIT_UNLOCKED);
> space->context_tbl[i] = ~0;
> }
>
> + for (i = 0, offset = 0; i < ARRAY_SIZE(space->session_tbl); i++) {
> + if (!space->session_tbl[i])
> + continue;
> +
> + rc = tpm2_save_context(chip, space->session_tbl[i],
> + space->session_buf, PAGE_SIZE,
> + &offset);
> +
> + if (rc == -ENOENT) {
> + /* handle error saving session, just forget it */
> + space->session_tbl[i] = 0;
> + } else if (rc < 0) {
> + tpm2_flush_space(chip);
> + return rc;
> + }
> + }
> +
> return 0;
> }
>
> @@ -425,7 +523,10 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,
>
> memcpy(&space->context_tbl, &chip->work_space.context_tbl,
> 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);
>
> return 0;
> }
> diff --git a/drivers/char/tpm/tpms-dev.c b/drivers/char/tpm/tpms-dev.c
> index 5720885..4c98db8 100644
> --- a/drivers/char/tpm/tpms-dev.c
> +++ b/drivers/char/tpm/tpms-dev.c
> @@ -39,7 +39,7 @@ static int tpms_release(struct inode *inode, struct file *file)
> struct tpms_priv *priv = container_of(fpriv, struct tpms_priv, priv);
>
> tpm_common_release(file, fpriv);
> - tpm2_del_space(&priv->space);
> + tpm2_del_space(fpriv->chip, &priv->space);
> kfree(priv);
>
> return 0;
> --
> 2.9.3
>

Next message: Potomski, MichalX: "[PATCH v2] scsi: ufs: Factor out ufshcd_read_desc_param"
Previous message: Stefan Lengfeld: "Re: [PATCH v3 2/2] drm/fb-helper: implement ioctl FBIO_WAITFORVSYNC"
In reply to: Jarkko Sakkinen: "[PATCH v2 7/7] tpm2: add session handle context saving and restoring to the space code"
Next in thread: Jarkko Sakkinen: "[PATCH v2 5/7] tpm: split out tpm-dev.c into tpm-dev.c and tpm-common-dev.c"
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