Re: [PATCH v3 04/16] tpm: call tpm2_flush_space() on error in tpm_try_transmit()

Stefan Berger
2018-11-05T22:01:55Z

On 11/4/18 8:45 PM, Jarkko Sakkinen wrote:
> Always call tpm2_flush_space() on failure in tpm_try_transmit() so that
> the volatile memory of the TPM gets cleared. If /dev/tpm0 does not have
> sufficient permissions (usually it has), this could leak to the leakage

leak ->lead

> of TPM objects. Through /dev/tpmrm0 this issue does not raise new
> security concerns.
>
> Cc: stable@vger.kernel.org
> Fixes: 745b361e989a ("tpm:tpm: infrastructure for TPM spaces")
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> ---
> drivers/char/tpm/tpm-interface.c | 28 +++++++++++++++++-----------
> drivers/char/tpm/tpm.h | 1 +
> drivers/char/tpm/tpm2-space.c | 2 +-
> 3 files changed, 19 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index 64510ed81b46..ecda6f96cde0 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -224,14 +224,14 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
>
> rc = tpm2_prepare_space(chip, space, ordinal, buf);
> if (rc)
> - goto out;
> + goto out_idle;
>
> rc = chip->ops->send(chip, buf, count);
> if (rc < 0) {
> if (rc != -EPIPE)
> dev_err(&chip->dev,
> "%s: tpm_send: error %d\n", __func__, rc);
> - goto out;
> + goto out_space;
> }
>
> if (chip->flags & TPM_CHIP_FLAG_IRQ)
> @@ -247,7 +247,7 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
> if (chip->ops->req_canceled(chip, status)) {
> dev_err(&chip->dev, "Operation Canceled\n");
> rc = -ECANCELED;
> - goto out;
> + goto out_space;
> }
>
> tpm_msleep(TPM_TIMEOUT_POLL);
> @@ -257,7 +257,7 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
> chip->ops->cancel(chip);
> dev_err(&chip->dev, "Operation Timed out\n");
> rc = -ETIME;
> - goto out;
> + goto out_space;
>
> out_recv:
> len = chip->ops->recv(chip, buf, bufsiz);
> @@ -265,22 +265,28 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
> rc = len;
> dev_err(&chip->dev,
> "tpm_transmit: tpm_recv: error %d\n", rc);
> - goto out;
> + goto out_idle;

Why not jump to out_space here and in 2 instances below?

> } else if (len < TPM_HEADER_SIZE) {
> rc = -EFAULT;
> - goto out;
> + goto out_idle;
> }
>
> if (len != be32_to_cpu(header->length)) {
> rc = -EFAULT;
> - goto out;
> + goto out_idle;
> }
>
> - rc = tpm2_commit_space(chip, space, ordinal, buf, &len);
> - if (rc)
> - dev_err(&chip->dev, "tpm2_commit_space: error %d\n", rc);
> +out_space:
> + if (rc) {
> + tpm2_flush_space(chip);
> + } else {
> + rc = tpm2_commit_space(chip, space, ordinal, buf, &len);
> + if (rc)
> + dev_err(&chip->dev, "tpm2_commit_space: error %d\n",
> + rc);
> + }
>
> -out:
> +out_idle:
> /* may fail but do not override previous error value in rc */
> tpm_go_idle(chip, flags);
>
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 49bca4d1e786..229ac42b644e 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -579,6 +579,7 @@ int tpm2_probe(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_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, 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 1131a8e7b79b..d53c882268ff 100644
> --- a/drivers/char/tpm/tpm2-space.c
> +++ b/drivers/char/tpm/tpm2-space.c
> @@ -162,7 +162,7 @@ static int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
> return 0;
> }
>
> -static void tpm2_flush_space(struct tpm_chip *chip)
> +void tpm2_flush_space(struct tpm_chip *chip)
> {
> struct tpm_space *space = &chip->work_space;
> int i;