diff mbox

tpm: fix a race condition in tpm2_unseal_trusted()

Message ID 1472366212-8571-1-git-send-email-jarkko.sakkinen@linux.intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Jarkko Sakkinen Aug. 28, 2016, 6:36 a.m. UTC 
Unseal and load operations should be done as an atomic operation. This
commit introduces unlocked tpm_transmit() so that tpm2_unseal_trusted()
can do the locking by itself.

v2: Introduced an unlocked unseal operation instead of changing locking
    strategy in order to make less intrusive bug fix and thus more
    backportable.

v3: Have also separate __tpm_transmit() that takes 'flags' in order to
    better localize the bug fix and make it easier to backport.

v4: Cleaned up the control flow in tpm2_unseal_trusted. Added the
    missing 'Fixes' line.

v5: Previous versions did not set the enum to any value, so it was set
    to zero. Changed enum to TPM_TRANSMIT_UNLOCKED because it is
    guaranteed to catch such situation. With change the common case
    adds so little clutter that the wrappers do not make sense anymore.

Fixes: 0fe5480303a1 ("keys, trusted: seal/unseal with TPM 2.0 chips")
CC: stable@vger.kernel.org
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 drivers/char/tpm/tpm-dev.c       |  2 +-
 drivers/char/tpm/tpm-interface.c | 51 ++++++++++++++++++++++------------------
 drivers/char/tpm/tpm-sysfs.c     |  2 +-
 drivers/char/tpm/tpm.h           | 12 ++++++----
 drivers/char/tpm/tpm2-cmd.c      | 34 ++++++++++++++++-----------
 5 files changed, 58 insertions(+), 43 deletions(-)

Comments

Jason Gunthorpe Aug. 28, 2016, 6:51 p.m. UTC | #1 
On Sun, Aug 28, 2016 at 08:36:52AM +0200, Jarkko Sakkinen wrote:
>  
> @@ -576,7 +576,8 @@ static int tpm2_load(struct tpm_chip *chip,
>  		goto out;
>  	}
>  
> -	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, "loading blob");
> +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, TPM_TRANSMIT_UNLOCKED,
> +			      "loading blob");

I still don't like this, required mutex's should not be split outside the
function that needs them without more a more obvious indication:

> +	mutex_lock(&chip->tpm_mutex);
>  	rc = tpm2_load(chip, payload, options, &blob_handle);
>  	if (rc)
> -		return rc;

I recommend you stick with the idiom and do this:

        mutex_lock(&chip->tpm_mutex);
  	rc = tpm2_load(chip, payload, options, &blob_handle, TPM_TRANSMIT_UNLOCKED);

Which makes it easy to see we are doing it right everywhere.

Jason

------------------------------------------------------------------------------
Jarkko Sakkinen Aug. 29, 2016, 3:25 p.m. UTC | #2 
On Sun, Aug 28, 2016 at 12:51:49PM -0600, Jason Gunthorpe wrote:
> On Sun, Aug 28, 2016 at 08:36:52AM +0200, Jarkko Sakkinen wrote:
> >  
> > @@ -576,7 +576,8 @@ static int tpm2_load(struct tpm_chip *chip,
> >  		goto out;
> >  	}
> >  
> > -	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, "loading blob");
> > +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, TPM_TRANSMIT_UNLOCKED,
> > +			      "loading blob");
> 
> I still don't like this, required mutex's should not be split outside the
> function that needs them without more a more obvious indication:
> 
> > +	mutex_lock(&chip->tpm_mutex);
> >  	rc = tpm2_load(chip, payload, options, &blob_handle);
> >  	if (rc)
> > -		return rc;
> 
> I recommend you stick with the idiom and do this:
> 
>         mutex_lock(&chip->tpm_mutex);
>   	rc = tpm2_load(chip, payload, options, &blob_handle, TPM_TRANSMIT_UNLOCKED);
> 
> Which makes it easy to see we are doing it right everywhere.

Why consume stack for unnecessary stuff? This is a static function. For
me this sounds like cutting hairs really.

One thing that would improve readability would be to rename internal
functions tpm2_load and tpm2_unseal to tpm2_load_cmd and tpm2_unseal_cmd
in order to underline that they are command wrappers and not to mix with
tpm2_unseal_trusted().

I've been thinking to move that kind of convetion at least with TPM2
specific stuff when a function is clearly a wrapper. It kind of
documents the call path. I.e. if function satifies a constraint that
it prepares a command blob, calls tpm_transmit_cmd once and then
returns results to the caller this would be the naming convention.

> Jason

/Jarkko

------------------------------------------------------------------------------
Jason Gunthorpe Aug. 29, 2016, 7:21 p.m. UTC | #3 
On Mon, Aug 29, 2016 at 06:25:21PM +0300, Jarkko Sakkinen wrote:
> On Sun, Aug 28, 2016 at 12:51:49PM -0600, Jason Gunthorpe wrote:
> > On Sun, Aug 28, 2016 at 08:36:52AM +0200, Jarkko Sakkinen wrote:
> > >  
> > > @@ -576,7 +576,8 @@ static int tpm2_load(struct tpm_chip *chip,
> > >  		goto out;
> > >  	}
> > >  
> > > -	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, "loading blob");
> > > +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, TPM_TRANSMIT_UNLOCKED,
> > > +			      "loading blob");
> > 
> > I still don't like this, required mutex's should not be split outside the
> > function that needs them without more a more obvious indication:
> > 
> > > +	mutex_lock(&chip->tpm_mutex);
> > >  	rc = tpm2_load(chip, payload, options, &blob_handle);
> > >  	if (rc)
> > > -		return rc;
> > 
> > I recommend you stick with the idiom and do this:
> > 
> >         mutex_lock(&chip->tpm_mutex);
> >   	rc = tpm2_load(chip, payload, options, &blob_handle, TPM_TRANSMIT_UNLOCKED);
> > 
> > Which makes it easy to see we are doing it right everywhere.
> 
> Why consume stack for unnecessary stuff? This is a static function. For
> me this sounds like cutting hairs really.

Well, tpm2_load looks like any other normal command that would grab
the mutex, so something has to be done to indicate to the reader it is
the unlocked version.

I wouldn't worry about the stack, the compiler will inline that away
anyhow.

> One thing that would improve readability would be to rename internal
> functions tpm2_load and tpm2_unseal to tpm2_load_cmd and tpm2_unseal_cmd
> in order to underline that they are command wrappers and not to mix with
> tpm2_unseal_trusted().

That seems reasonable as well, as long as all _cmd varients are unlocked.

Jason

------------------------------------------------------------------------------
Jarkko Sakkinen Aug. 29, 2016, 7:40 p.m. UTC | #4 
On Mon, Aug 29, 2016 at 01:21:10PM -0600, Jason Gunthorpe wrote:
> On Mon, Aug 29, 2016 at 06:25:21PM +0300, Jarkko Sakkinen wrote:
> > On Sun, Aug 28, 2016 at 12:51:49PM -0600, Jason Gunthorpe wrote:
> > > On Sun, Aug 28, 2016 at 08:36:52AM +0200, Jarkko Sakkinen wrote:
> > > >  
> > > > @@ -576,7 +576,8 @@ static int tpm2_load(struct tpm_chip *chip,
> > > >  		goto out;
> > > >  	}
> > > >  
> > > > -	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, "loading blob");
> > > > +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, TPM_TRANSMIT_UNLOCKED,
> > > > +			      "loading blob");
> > > 
> > > I still don't like this, required mutex's should not be split outside the
> > > function that needs them without more a more obvious indication:
> > > 
> > > > +	mutex_lock(&chip->tpm_mutex);
> > > >  	rc = tpm2_load(chip, payload, options, &blob_handle);
> > > >  	if (rc)
> > > > -		return rc;
> > > 
> > > I recommend you stick with the idiom and do this:
> > > 
> > >         mutex_lock(&chip->tpm_mutex);
> > >   	rc = tpm2_load(chip, payload, options, &blob_handle, TPM_TRANSMIT_UNLOCKED);
> > > 
> > > Which makes it easy to see we are doing it right everywhere.
> > 
> > Why consume stack for unnecessary stuff? This is a static function. For
> > me this sounds like cutting hairs really.
> 
> Well, tpm2_load looks like any other normal command that would grab
> the mutex, so something has to be done to indicate to the reader it is
> the unlocked version.
> 
> I wouldn't worry about the stack, the compiler will inline that away
> anyhow.
> 
> > One thing that would improve readability would be to rename internal
> > functions tpm2_load and tpm2_unseal to tpm2_load_cmd and tpm2_unseal_cmd
> > in order to underline that they are command wrappers and not to mix with
> > tpm2_unseal_trusted().
> 
> That seems reasonable as well, as long as all _cmd varients are unlocked.

I think this more reasonable argument for your proposal than previous
ones for the flags parameter. Or maybe you had this argument in earlier
responses but I just failed to decipher it.

I can buy this.

> Jason

/Jarkko

------------------------------------------------------------------------------
Jarkko Sakkinen Aug. 29, 2016, 8:03 p.m. UTC | #5 
On Mon, Aug 29, 2016 at 10:40:27PM +0300, Jarkko Sakkinen wrote:
> On Mon, Aug 29, 2016 at 01:21:10PM -0600, Jason Gunthorpe wrote:
> > On Mon, Aug 29, 2016 at 06:25:21PM +0300, Jarkko Sakkinen wrote:
> > > On Sun, Aug 28, 2016 at 12:51:49PM -0600, Jason Gunthorpe wrote:
> > > > On Sun, Aug 28, 2016 at 08:36:52AM +0200, Jarkko Sakkinen wrote:
> > > > >  
> > > > > @@ -576,7 +576,8 @@ static int tpm2_load(struct tpm_chip *chip,
> > > > >  		goto out;
> > > > >  	}
> > > > >  
> > > > > -	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, "loading blob");
> > > > > +	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, TPM_TRANSMIT_UNLOCKED,
> > > > > +			      "loading blob");
> > > > 
> > > > I still don't like this, required mutex's should not be split outside the
> > > > function that needs them without more a more obvious indication:
> > > > 
> > > > > +	mutex_lock(&chip->tpm_mutex);
> > > > >  	rc = tpm2_load(chip, payload, options, &blob_handle);
> > > > >  	if (rc)
> > > > > -		return rc;
> > > > 
> > > > I recommend you stick with the idiom and do this:
> > > > 
> > > >         mutex_lock(&chip->tpm_mutex);
> > > >   	rc = tpm2_load(chip, payload, options, &blob_handle, TPM_TRANSMIT_UNLOCKED);
> > > > 
> > > > Which makes it easy to see we are doing it right everywhere.
> > > 
> > > Why consume stack for unnecessary stuff? This is a static function. For
> > > me this sounds like cutting hairs really.
> > 
> > Well, tpm2_load looks like any other normal command that would grab
> > the mutex, so something has to be done to indicate to the reader it is
> > the unlocked version.
> > 
> > I wouldn't worry about the stack, the compiler will inline that away
> > anyhow.
> > 
> > > One thing that would improve readability would be to rename internal
> > > functions tpm2_load and tpm2_unseal to tpm2_load_cmd and tpm2_unseal_cmd
> > > in order to underline that they are command wrappers and not to mix with
> > > tpm2_unseal_trusted().
> > 
> > That seems reasonable as well, as long as all _cmd varients are unlocked.
> 
> I think this more reasonable argument for your proposal than previous
> ones for the flags parameter. Or maybe you had this argument in earlier
> responses but I just failed to decipher it.
> 
> I can buy this.

I fix the comments as well because they have some errors concerning
return value and also do not match guidelines of [1] now that I'm at it.

I will also add documentation comments for tpm2_unseal_cmd,
tpm2_load_cmd and tpm2_flush_context_cmd. Do you think it is sufficient
to say "Return: same as with tpm_transmit_cmd"?

[1]  https://www.kernel.org/doc/Documentation/kernel-doc-nano-HOWTO.txt

/Jarkko

------------------------------------------------------------------------------
Jason Gunthorpe Aug. 29, 2016, 8:07 p.m. UTC | #6 
On Mon, Aug 29, 2016 at 11:03:26PM +0300, Jarkko Sakkinen wrote:

> I will also add documentation comments for tpm2_unseal_cmd,
> tpm2_load_cmd and tpm2_flush_context_cmd. Do you think it is sufficient
> to say "Return: same as with tpm_transmit_cmd"?

yes

Jason

------------------------------------------------------------------------------
diff mbox

Patch

diff --git a/drivers/char/tpm/tpm-dev.c b/drivers/char/tpm/tpm-dev.c
index f5d4521..912ad30 100644
--- a/drivers/char/tpm/tpm-dev.c
+++ b/drivers/char/tpm/tpm-dev.c
@@ -145,7 +145,7 @@  static ssize_t tpm_write(struct file *file, const char __user *buf,
 		return -EPIPE;
 	}
 	out_size = tpm_transmit(priv->chip, priv->data_buffer,
-				sizeof(priv->data_buffer));
+				sizeof(priv->data_buffer), 0);
 
 	tpm_put_ops(priv->chip);
 	if (out_size < 0) {
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 1abe2d7..aef20ee 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -330,8 +330,8 @@  EXPORT_SYMBOL_GPL(tpm_calc_ordinal_duration);
 /*
  * Internal kernel interface to transmit TPM commands
  */
-ssize_t tpm_transmit(struct tpm_chip *chip, const char *buf,
-		     size_t bufsiz)
+ssize_t tpm_transmit(struct tpm_chip *chip, const u8 *buf, size_t bufsiz,
+		     unsigned int flags)
 {
 	ssize_t rc;
 	u32 count, ordinal;
@@ -350,7 +350,8 @@  ssize_t tpm_transmit(struct tpm_chip *chip, const char *buf,
 		return -E2BIG;
 	}
 
-	mutex_lock(&chip->tpm_mutex);
+	if (!(flags & TPM_TRANSMIT_UNLOCKED))
+		mutex_lock(&chip->tpm_mutex);
 
 	rc = chip->ops->send(chip, (u8 *) buf, count);
 	if (rc < 0) {
@@ -393,20 +394,21 @@  out_recv:
 		dev_err(&chip->dev,
 			"tpm_transmit: tpm_recv: error %zd\n", rc);
 out:
-	mutex_unlock(&chip->tpm_mutex);
+	if (!(flags & TPM_TRANSMIT_UNLOCKED))
+		mutex_unlock(&chip->tpm_mutex);
 	return rc;
 }
 
 #define TPM_DIGEST_SIZE 20
 #define TPM_RET_CODE_IDX 6
 
-ssize_t tpm_transmit_cmd(struct tpm_chip *chip, void *cmd,
-			 int len, const char *desc)
+ssize_t tpm_transmit_cmd(struct tpm_chip *chip, const void *cmd,
+			 int len, unsigned int flags, const char *desc)
 {
-	struct tpm_output_header *header;
+	const struct tpm_output_header *header;
 	int err;
 
-	len = tpm_transmit(chip, (u8 *) cmd, len);
+	len = tpm_transmit(chip, (const u8 *)cmd, len, flags);
 	if (len <  0)
 		return len;
 	else if (len < TPM_HEADER_SIZE)
@@ -453,7 +455,8 @@  ssize_t tpm_getcap(struct tpm_chip *chip, __be32 subcap_id, cap_t *cap,
 		tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
 		tpm_cmd.params.getcap_in.subcap = subcap_id;
 	}
-	rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE, desc);
+	rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE, 0,
+			      desc);
 	if (!rc)
 		*cap = tpm_cmd.params.getcap_out.cap;
 	return rc;
@@ -469,7 +472,7 @@  void tpm_gen_interrupt(struct tpm_chip *chip)
 	tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
 	tpm_cmd.params.getcap_in.subcap = TPM_CAP_PROP_TIS_TIMEOUT;
 
-	rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE,
+	rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE, 0,
 			      "attempting to determine the timeouts");
 }
 EXPORT_SYMBOL_GPL(tpm_gen_interrupt);
@@ -490,7 +493,7 @@  static int tpm_startup(struct tpm_chip *chip, __be16 startup_type)
 	start_cmd.header.in = tpm_startup_header;
 
 	start_cmd.params.startup_in.startup_type = startup_type;
-	return tpm_transmit_cmd(chip, &start_cmd, TPM_INTERNAL_RESULT_SIZE,
+	return tpm_transmit_cmd(chip, &start_cmd, TPM_INTERNAL_RESULT_SIZE, 0,
 				"attempting to start the TPM");
 }
 
@@ -521,7 +524,8 @@  int tpm_get_timeouts(struct tpm_chip *chip)
 	tpm_cmd.params.getcap_in.cap = TPM_CAP_PROP;
 	tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
 	tpm_cmd.params.getcap_in.subcap = TPM_CAP_PROP_TIS_TIMEOUT;
-	rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE, NULL);
+	rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE, 0,
+			      NULL);
 
 	if (rc == TPM_ERR_INVALID_POSTINIT) {
 		/* The TPM is not started, we are the first to talk to it.
@@ -535,7 +539,7 @@  int tpm_get_timeouts(struct tpm_chip *chip)
 		tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
 		tpm_cmd.params.getcap_in.subcap = TPM_CAP_PROP_TIS_TIMEOUT;
 		rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE,
-				  NULL);
+				      0, NULL);
 	}
 	if (rc) {
 		dev_err(&chip->dev,
@@ -596,7 +600,7 @@  duration:
 	tpm_cmd.params.getcap_in.subcap_size = cpu_to_be32(4);
 	tpm_cmd.params.getcap_in.subcap = TPM_CAP_PROP_TIS_DURATION;
 
-	rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE,
+	rc = tpm_transmit_cmd(chip, &tpm_cmd, TPM_INTERNAL_RESULT_SIZE, 0,
 			      "attempting to determine the durations");
 	if (rc)
 		return rc;
@@ -652,7 +656,7 @@  static int tpm_continue_selftest(struct tpm_chip *chip)
 	struct tpm_cmd_t cmd;
 
 	cmd.header.in = continue_selftest_header;
-	rc = tpm_transmit_cmd(chip, &cmd, CONTINUE_SELFTEST_RESULT_SIZE,
+	rc = tpm_transmit_cmd(chip, &cmd, CONTINUE_SELFTEST_RESULT_SIZE, 0,
 			      "continue selftest");
 	return rc;
 }
@@ -672,7 +676,7 @@  int tpm_pcr_read_dev(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
 
 	cmd.header.in = pcrread_header;
 	cmd.params.pcrread_in.pcr_idx = cpu_to_be32(pcr_idx);
-	rc = tpm_transmit_cmd(chip, &cmd, READ_PCR_RESULT_SIZE,
+	rc = tpm_transmit_cmd(chip, &cmd, READ_PCR_RESULT_SIZE, 0,
 			      "attempting to read a pcr value");
 
 	if (rc == 0)
@@ -770,7 +774,7 @@  int tpm_pcr_extend(u32 chip_num, int pcr_idx, const u8 *hash)
 	cmd.header.in = pcrextend_header;
 	cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(pcr_idx);
 	memcpy(cmd.params.pcrextend_in.hash, hash, TPM_DIGEST_SIZE);
-	rc = tpm_transmit_cmd(chip, &cmd, EXTEND_PCR_RESULT_SIZE,
+	rc = tpm_transmit_cmd(chip, &cmd, EXTEND_PCR_RESULT_SIZE, 0,
 			      "attempting extend a PCR value");
 
 	tpm_put_ops(chip);
@@ -809,7 +813,7 @@  int tpm_do_selftest(struct tpm_chip *chip)
 		/* Attempt to read a PCR value */
 		cmd.header.in = pcrread_header;
 		cmd.params.pcrread_in.pcr_idx = cpu_to_be32(0);
-		rc = tpm_transmit(chip, (u8 *) &cmd, READ_PCR_RESULT_SIZE);
+		rc = tpm_transmit(chip, (u8 *) &cmd, READ_PCR_RESULT_SIZE, 0);
 		/* Some buggy TPMs will not respond to tpm_tis_ready() for
 		 * around 300ms while the self test is ongoing, keep trying
 		 * until the self test duration expires. */
@@ -879,7 +883,7 @@  int tpm_send(u32 chip_num, void *cmd, size_t buflen)
 	if (chip == NULL)
 		return -ENODEV;
 
-	rc = tpm_transmit_cmd(chip, cmd, buflen, "attempting tpm_cmd");
+	rc = tpm_transmit_cmd(chip, cmd, buflen, 0, "attempting tpm_cmd");
 
 	tpm_put_ops(chip);
 	return rc;
@@ -981,14 +985,15 @@  int tpm_pm_suspend(struct device *dev)
 		cmd.params.pcrextend_in.pcr_idx = cpu_to_be32(tpm_suspend_pcr);
 		memcpy(cmd.params.pcrextend_in.hash, dummy_hash,
 		       TPM_DIGEST_SIZE);
-		rc = tpm_transmit_cmd(chip, &cmd, EXTEND_PCR_RESULT_SIZE,
+		rc = tpm_transmit_cmd(chip, &cmd, EXTEND_PCR_RESULT_SIZE, 0,
 				      "extending dummy pcr before suspend");
 	}
 
 	/* now do the actual savestate */
 	for (try = 0; try < TPM_RETRY; try++) {
 		cmd.header.in = savestate_header;
-		rc = tpm_transmit_cmd(chip, &cmd, SAVESTATE_RESULT_SIZE, NULL);
+		rc = tpm_transmit_cmd(chip, &cmd, SAVESTATE_RESULT_SIZE, 0,
+				      NULL);
 
 		/*
 		 * If the TPM indicates that it is too busy to respond to
@@ -1072,8 +1077,8 @@  int tpm_get_random(u32 chip_num, u8 *out, size_t max)
 		tpm_cmd.params.getrandom_in.num_bytes = cpu_to_be32(num_bytes);
 
 		err = tpm_transmit_cmd(chip, &tpm_cmd,
-				   TPM_GETRANDOM_RESULT_SIZE + num_bytes,
-				   "attempting get random");
+				       TPM_GETRANDOM_RESULT_SIZE + num_bytes,
+				       0, "attempting get random");
 		if (err)
 			break;
 
diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index b46cf70..e1f7236 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -39,7 +39,7 @@  static ssize_t pubek_show(struct device *dev, struct device_attribute *attr,
 	struct tpm_chip *chip = to_tpm_chip(dev);
 
 	tpm_cmd.header.in = tpm_readpubek_header;
-	err = tpm_transmit_cmd(chip, &tpm_cmd, READ_PUBEK_RESULT_SIZE,
+	err = tpm_transmit_cmd(chip, &tpm_cmd, READ_PUBEK_RESULT_SIZE, 0,
 			       "attempting to read the PUBEK");
 	if (err)
 		goto out;
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 3e32d5b..b0585e9 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -476,12 +476,16 @@  extern dev_t tpm_devt;
 extern const struct file_operations tpm_fops;
 extern struct idr dev_nums_idr;
 
+enum tpm_transmit_flags {
+	TPM_TRANSMIT_UNLOCKED	= BIT(0),
+};
+
+ssize_t tpm_transmit(struct tpm_chip *chip, const u8 *buf, size_t bufsiz,
+		     unsigned int flags);
+ssize_t tpm_transmit_cmd(struct tpm_chip *chip, const void *cmd, int len,
+			 unsigned int flags, const char *desc);
 ssize_t tpm_getcap(struct tpm_chip *chip, __be32 subcap_id, cap_t *cap,
 		   const char *desc);
-ssize_t tpm_transmit(struct tpm_chip *chip, const char *buf,
-		     size_t bufsiz);
-ssize_t tpm_transmit_cmd(struct tpm_chip *chip, void *cmd, int len,
-			 const char *desc);
 extern int tpm_get_timeouts(struct tpm_chip *);
 extern void tpm_gen_interrupt(struct tpm_chip *);
 int tpm1_auto_startup(struct tpm_chip *chip);
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 08c7e23..5452ba7 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -282,7 +282,7 @@  int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf)
 	       sizeof(cmd.params.pcrread_in.pcr_select));
 	cmd.params.pcrread_in.pcr_select[pcr_idx >> 3] = 1 << (pcr_idx & 0x7);
 
-	rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd),
+	rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), 0,
 			      "attempting to read a pcr value");
 	if (rc == 0) {
 		buf = cmd.params.pcrread_out.digest;
@@ -330,7 +330,7 @@  int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, const u8 *hash)
 	cmd.params.pcrextend_in.hash_alg = cpu_to_be16(TPM2_ALG_SHA1);
 	memcpy(cmd.params.pcrextend_in.digest, hash, TPM_DIGEST_SIZE);
 
-	rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd),
+	rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), 0,
 			      "attempting extend a PCR value");
 
 	return rc;
@@ -376,7 +376,7 @@  int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max)
 		cmd.header.in = tpm2_getrandom_header;
 		cmd.params.getrandom_in.size = cpu_to_be16(num_bytes);
 
-		err = tpm_transmit_cmd(chip, &cmd, sizeof(cmd),
+		err = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), 0,
 				       "attempting get random");
 		if (err)
 			break;
@@ -512,7 +512,7 @@  int tpm2_seal_trusted(struct tpm_chip *chip,
 		goto out;
 	}
 
-	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, "sealing data");
+	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, 0, "sealing data");
 	if (rc)
 		goto out;
 
@@ -576,7 +576,8 @@  static int tpm2_load(struct tpm_chip *chip,
 		goto out;
 	}
 
-	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, "loading blob");
+	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, TPM_TRANSMIT_UNLOCKED,
+			      "loading blob");
 	if (!rc)
 		*blob_handle = be32_to_cpup(
 			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
@@ -604,7 +605,8 @@  static void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
 
 	tpm_buf_append_u32(&buf, handle);
 
-	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, "flushing context");
+	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, TPM_TRANSMIT_UNLOCKED,
+			      "flushing context");
 	if (rc)
 		dev_warn(&chip->dev, "0x%08x was not flushed, rc=%d\n", handle,
 			 rc);
@@ -635,7 +637,8 @@  static int tpm2_unseal(struct tpm_chip *chip,
 			     options->blobauth /* hmac */,
 			     TPM_DIGEST_SIZE);
 
-	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, "unsealing");
+	rc = tpm_transmit_cmd(chip, buf.data, PAGE_SIZE, TPM_TRANSMIT_UNLOCKED,
+			      "unsealing");
 	if (rc > 0)
 		rc = -EPERM;
 
@@ -668,14 +671,17 @@  int tpm2_unseal_trusted(struct tpm_chip *chip,
 	u32 blob_handle;
 	int rc;
 
+	mutex_lock(&chip->tpm_mutex);
 	rc = tpm2_load(chip, payload, options, &blob_handle);
 	if (rc)
-		return rc;
+		goto out;
 
 	rc = tpm2_unseal(chip, payload, options, blob_handle);
 
 	tpm2_flush_context(chip, blob_handle);
 
+out:
+	mutex_unlock(&chip->tpm_mutex);
 	return rc;
 }
 
@@ -701,7 +707,7 @@  ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,  u32 *value,
 	cmd.params.get_tpm_pt_in.property_id = cpu_to_be32(property_id);
 	cmd.params.get_tpm_pt_in.property_cnt = cpu_to_be32(1);
 
-	rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), desc);
+	rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), 0, desc);
 	if (!rc)
 		*value = be32_to_cpu(cmd.params.get_tpm_pt_out.value);
 
@@ -735,7 +741,7 @@  static int tpm2_startup(struct tpm_chip *chip, u16 startup_type)
 	cmd.header.in = tpm2_startup_header;
 
 	cmd.params.startup_in.startup_type = cpu_to_be16(startup_type);
-	return tpm_transmit_cmd(chip, &cmd, sizeof(cmd),
+	return tpm_transmit_cmd(chip, &cmd, sizeof(cmd), 0,
 				"attempting to start the TPM");
 }
 
@@ -763,7 +769,7 @@  void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type)
 	cmd.header.in = tpm2_shutdown_header;
 	cmd.params.startup_in.startup_type = cpu_to_be16(shutdown_type);
 
-	rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), "stopping the TPM");
+	rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), 0, "stopping the TPM");
 
 	/* In places where shutdown command is sent there's no much we can do
 	 * except print the error code on a system failure.
@@ -828,7 +834,7 @@  static int tpm2_start_selftest(struct tpm_chip *chip, bool full)
 	cmd.header.in = tpm2_selftest_header;
 	cmd.params.selftest_in.full_test = full;
 
-	rc = tpm_transmit_cmd(chip, &cmd, TPM2_SELF_TEST_IN_SIZE,
+	rc = tpm_transmit_cmd(chip, &cmd, TPM2_SELF_TEST_IN_SIZE, 0,
 			      "continue selftest");
 
 	/* At least some prototype chips seem to give RC_TESTING error
@@ -880,7 +886,7 @@  static int tpm2_do_selftest(struct tpm_chip *chip)
 		cmd.params.pcrread_in.pcr_select[1] = 0x00;
 		cmd.params.pcrread_in.pcr_select[2] = 0x00;
 
-		rc = tpm_transmit_cmd(chip, (u8 *) &cmd, sizeof(cmd), NULL);
+		rc = tpm_transmit_cmd(chip, &cmd, sizeof(cmd), 0, NULL);
 		if (rc < 0)
 			break;
 
@@ -928,7 +934,7 @@  int tpm2_probe(struct tpm_chip *chip)
 	cmd.params.get_tpm_pt_in.property_id = cpu_to_be32(0x100);
 	cmd.params.get_tpm_pt_in.property_cnt = cpu_to_be32(1);
 
-	rc = tpm_transmit(chip, (const char *) &cmd, sizeof(cmd));
+	rc = tpm_transmit(chip, (const u8 *)&cmd, sizeof(cmd), 0);
 	if (rc <  0)
 		return rc;
 	else if (rc < TPM_HEADER_SIZE)