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Re: [PATCH v5 04/17] tpm: call tpm2_flush_space() on error in tpm_try_transmit()




On 11/8/18 9:15 AM, 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 lead to the leakage
of TPM objects. Through /dev/tpmrm0 this issue does not raise any new
security concerns.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 745b361e989a ("tpm:tpm: infrastructure for TPM spaces")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>

Reviewed-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>


---
  drivers/char/tpm/tpm-interface.c | 33 +++++++++++++++-----------------
  drivers/char/tpm/tpm.h           |  1 +
  drivers/char/tpm/tpm2-space.c    |  2 +-
  3 files changed, 17 insertions(+), 19 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 64510ed81b46..c9efd1b9fd2c 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);
@@ -257,30 +257,27 @@ 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);
  	if (len < 0) {
  		rc = len;
-		dev_err(&chip->dev,
-			"tpm_transmit: tpm_recv: error %d\n", rc);
-		goto out;
-	} else if (len < TPM_HEADER_SIZE) {
+		dev_err(&chip->dev, "tpm_transmit: tpm_recv: error %d\n", rc);
+	} else if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
  		rc = -EFAULT;
-		goto out;
-	}

-	if (len != be32_to_cpu(header->length)) {
-		rc = -EFAULT;
-		goto out;
+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);
  	}

-	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;