[PATCH v3] tpm: Actually fail on TPM errors during "get random"

[PATCH v3] tpm: Actually fail on TPM errors during "get random"

[Kees Cook]

A "get random" may fail with a TPM error, but those codes were returned
as-is to the caller, which assumed the result was the number of bytes
that had been written to the target buffer, which could lead to a kernel
heap memory exposure and over-read.

This fixes tpm1_get_random() to mask positive TPM errors into -EIO, as
before.

[   18.092103] tpm tpm0: A TPM error (379) occurred attempting get random
[   18.092106] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmalloc-64' (offset 0, size 379)!

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1650989
Reported-by: Phil Baker <baker1tex@gmail.com>
Reported-by: Craig Robson <craig@zhatt.com>
Fixes: 7aee9c52d7ac ("tpm: tpm1: rewrite tpm1_get_random() using tpm_buf structure")
Cc: Laura Abbott <labbott@redhat.com>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
v3: fix never-succeed, limit checks to tpm cmd return (James, Jason)
v2: also fix tpm2 implementation (Jason Gunthorpe)
---
 drivers/char/tpm/tpm1-cmd.c | 7 +++++--
 drivers/char/tpm/tpm2-cmd.c | 7 +++++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index 85dcf2654d11..faacbe1ffa1a 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -510,7 +510,7 @@ struct tpm1_get_random_out {
  *
  * Return:
  * *  number of bytes read
- * * -errno or a TPM return code otherwise
+ * * -errno (positive TPM return codes are masked to -EIO)
  */
 int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 {
@@ -531,8 +531,11 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 
 		rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
 				      "attempting get random");
-		if (rc)
+		if (rc) {
+			if (rc > 0)
+				rc = -EIO;
 			goto out;
+		}
 
 		out = (struct tpm1_get_random_out *)&buf.data[TPM_HEADER_SIZE];
 
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index e74c5b7b64bf..8ffa6af61580 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -301,7 +301,7 @@ struct tpm2_get_random_out {
  *
  * Return:
  *   size of the buffer on success,
- *   -errno otherwise
+ *   -errno otherwise ((positive TPM return codes are masked to -EIO)
  */
 int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 {
@@ -328,8 +328,11 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 				       offsetof(struct tpm2_get_random_out,
 						buffer),
 				       "attempting get random");
-		if (err)
+		if (err) {
+			if (err > 0)
+				err = -EIO;
 			goto out;
+		}
 
 		out = (struct tpm2_get_random_out *)
 			&buf.data[TPM_HEADER_SIZE];
-- 
2.17.1


-- 
Kees Cook

Re: [PATCH v3] tpm: Actually fail on TPM errors during "get random"

[Jason Gunthorpe]

On Mon, Apr 01, 2019 at 12:06:07PM -0700, Kees Cook wrote:
> A "get random" may fail with a TPM error, but those codes were returned
> as-is to the caller, which assumed the result was the number of bytes
> that had been written to the target buffer, which could lead to a kernel
> heap memory exposure and over-read.
> 
> This fixes tpm1_get_random() to mask positive TPM errors into -EIO, as
> before.
> 
> [   18.092103] tpm tpm0: A TPM error (379) occurred attempting get random
> [   18.092106] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmalloc-64' (offset 0, size 379)!
> 
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1650989
> Reported-by: Phil Baker <baker1tex@gmail.com>
> Reported-by: Craig Robson <craig@zhatt.com>
> Fixes: 7aee9c52d7ac ("tpm: tpm1: rewrite tpm1_get_random() using tpm_buf structure")
> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Tomas Winkler <tomas.winkler@intel.com>
> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> v3: fix never-succeed, limit checks to tpm cmd return (James, Jason)
> v2: also fix tpm2 implementation (Jason Gunthorpe)
>  drivers/char/tpm/tpm1-cmd.c | 7 +++++--
>  drivers/char/tpm/tpm2-cmd.c | 7 +++++--
>  2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
> index 85dcf2654d11..faacbe1ffa1a 100644
> +++ b/drivers/char/tpm/tpm1-cmd.c
> @@ -510,7 +510,7 @@ struct tpm1_get_random_out {
>   *
>   * Return:
>   * *  number of bytes read
> - * * -errno or a TPM return code otherwise
> + * * -errno (positive TPM return codes are masked to -EIO)
>   */
>  int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  {
> @@ -531,8 +531,11 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  
>  		rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
>  				      "attempting get random");
> -		if (rc)
> +		if (rc) {
> +			if (rc > 0)
> +				rc = -EIO;
>  			goto out;
> +		}
>  
>  		out = (struct tpm1_get_random_out *)&buf.data[TPM_HEADER_SIZE];
>  
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index e74c5b7b64bf..8ffa6af61580 100644
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -301,7 +301,7 @@ struct tpm2_get_random_out {
>   *
>   * Return:
>   *   size of the buffer on success,
> - *   -errno otherwise
> + *   -errno otherwise ((positive TPM return codes are masked to -EIO)

Extra bracket, but otherwise looks fine to me

Jason

Re: [PATCH v3] tpm: Actually fail on TPM errors during "get random"

[Kees Cook]

On Mon, Apr 1, 2019 at 12:09 PM Jason Gunthorpe <jgg@ziepe.ca> wrote:
> > + *   -errno otherwise ((positive TPM return codes are masked to -EIO)
>
> Extra bracket, but otherwise looks fine to me

Thanks! (And I guess it's time for lunch so I can take a break and
learn how to type again...)

-- 
Kees Cook

RE: [PATCH v3] tpm: Actually fail on TPM errors during "get random"

[Winkler, Tomas]

> 
> A "get random" may fail with a TPM error, but those codes were returned as-is
> to the caller, which assumed the result was the number of bytes that had been
> written to the target buffer, which could lead to a kernel heap memory
> exposure and over-read.
> 
> This fixes tpm1_get_random() to mask positive TPM errors into -EIO, as before.
> 
> [   18.092103] tpm tpm0: A TPM error (379) occurred attempting get random
> [   18.092106] usercopy: Kernel memory exposure attempt detected from SLUB
> object 'kmalloc-64' (offset 0, size 379)!
> 
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1650989
> Reported-by: Phil Baker <baker1tex@gmail.com>
> Reported-by: Craig Robson <craig@zhatt.com>
> Fixes: 7aee9c52d7ac ("tpm: tpm1: rewrite tpm1_get_random() using tpm_buf
> structure")
> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Tomas Winkler <tomas.winkler@intel.com>
> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> v3: fix never-succeed, limit checks to tpm cmd return (James, Jason)
> v2: also fix tpm2 implementation (Jason Gunthorpe)
Looks good to me.
Thanks
Tomas

> ---
>  drivers/char/tpm/tpm1-cmd.c | 7 +++++--  drivers/char/tpm/tpm2-cmd.c | 7
> +++++--
>  2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
> index 85dcf2654d11..faacbe1ffa1a 100644
> --- a/drivers/char/tpm/tpm1-cmd.c
> +++ b/drivers/char/tpm/tpm1-cmd.c
> @@ -510,7 +510,7 @@ struct tpm1_get_random_out {
>   *
>   * Return:
>   * *  number of bytes read
> - * * -errno or a TPM return code otherwise
> + * * -errno (positive TPM return codes are masked to -EIO)
>   */
>  int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)  { @@ -
> 531,8 +531,11 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest,
> size_t max)
> 
>  		rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
>  				      "attempting get random");
> -		if (rc)
> +		if (rc) {
> +			if (rc > 0)
> +				rc = -EIO;
>  			goto out;
> +		}
> 
>  		out = (struct tpm1_get_random_out
> *)&buf.data[TPM_HEADER_SIZE];
> 
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index e74c5b7b64bf..8ffa6af61580 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -301,7 +301,7 @@ struct tpm2_get_random_out {
>   *
>   * Return:
>   *   size of the buffer on success,
> - *   -errno otherwise
> + *   -errno otherwise ((positive TPM return codes are masked to -EIO)
>   */
>  int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)  { @@ -
> 328,8 +328,11 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest,
> size_t max)
>  				       offsetof(struct tpm2_get_random_out,
>  						buffer),
>  				       "attempting get random");
> -		if (err)
> +		if (err) {
> +			if (err > 0)
> +				err = -EIO;
>  			goto out;
> +		}
> 
>  		out = (struct tpm2_get_random_out *)
>  			&buf.data[TPM_HEADER_SIZE];
> --
> 2.17.1
> 
> 
> --
> Kees Cook

Re: [PATCH v3] tpm: Actually fail on TPM errors during "get random"

[Jarkko Sakkinen]

On Mon, Apr 01, 2019 at 12:06:07PM -0700, Kees Cook wrote:
> A "get random" may fail with a TPM error, but those codes were returned
> as-is to the caller, which assumed the result was the number of bytes
> that had been written to the target buffer, which could lead to a kernel
> heap memory exposure and over-read.
> 
> This fixes tpm1_get_random() to mask positive TPM errors into -EIO, as
> before.
> 
> [   18.092103] tpm tpm0: A TPM error (379) occurred attempting get random
> [   18.092106] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmalloc-64' (offset 0, size 379)!
> 
> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1650989
> Reported-by: Phil Baker <baker1tex@gmail.com>
> Reported-by: Craig Robson <craig@zhatt.com>
> Fixes: 7aee9c52d7ac ("tpm: tpm1: rewrite tpm1_get_random() using tpm_buf structure")
> Cc: Laura Abbott <labbott@redhat.com>
> Cc: Tomas Winkler <tomas.winkler@intel.com>
> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> v3: fix never-succeed, limit checks to tpm cmd return (James, Jason)
> v2: also fix tpm2 implementation (Jason Gunthorpe)
> ---
>  drivers/char/tpm/tpm1-cmd.c | 7 +++++--
>  drivers/char/tpm/tpm2-cmd.c | 7 +++++--
>  2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
> index 85dcf2654d11..faacbe1ffa1a 100644
> --- a/drivers/char/tpm/tpm1-cmd.c
> +++ b/drivers/char/tpm/tpm1-cmd.c
> @@ -510,7 +510,7 @@ struct tpm1_get_random_out {
>   *
>   * Return:
>   * *  number of bytes read
> - * * -errno or a TPM return code otherwise
> + * * -errno (positive TPM return codes are masked to -EIO)
>   */
>  int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  {
> @@ -531,8 +531,11 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  
>  		rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
>  				      "attempting get random");
> -		if (rc)
> +		if (rc) {
> +			if (rc > 0)
> +				rc = -EIO;
>  			goto out;
> +		}
>  
>  		out = (struct tpm1_get_random_out *)&buf.data[TPM_HEADER_SIZE];
>  
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index e74c5b7b64bf..8ffa6af61580 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -301,7 +301,7 @@ struct tpm2_get_random_out {
>   *
>   * Return:
>   *   size of the buffer on success,
> - *   -errno otherwise
> + *   -errno otherwise ((positive TPM return codes are masked to -EIO)
>   */
>  int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  {
> @@ -328,8 +328,11 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  				       offsetof(struct tpm2_get_random_out,
>  						buffer),
>  				       "attempting get random");
> -		if (err)
> +		if (err) {
> +			if (err > 0)
> +				err = -EIO;
>  			goto out;
> +		}
>  
>  		out = (struct tpm2_get_random_out *)
>  			&buf.data[TPM_HEADER_SIZE];
> -- 
> 2.17.1
> 
> 
> -- 
> Kees Cook

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

/Jarkko

Re: [PATCH v3] tpm: Actually fail on TPM errors during "get random"

[Jarkko Sakkinen]

On Tue, Apr 02, 2019 at 02:46:25AM +0300, Jarkko Sakkinen wrote:
> On Mon, Apr 01, 2019 at 12:06:07PM -0700, Kees Cook wrote:
> > A "get random" may fail with a TPM error, but those codes were returned
> > as-is to the caller, which assumed the result was the number of bytes
> > that had been written to the target buffer, which could lead to a kernel
> > heap memory exposure and over-read.
> > 
> > This fixes tpm1_get_random() to mask positive TPM errors into -EIO, as
> > before.
> > 
> > [   18.092103] tpm tpm0: A TPM error (379) occurred attempting get random
> > [   18.092106] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmalloc-64' (offset 0, size 379)!
> > 
> > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1650989
> > Reported-by: Phil Baker <baker1tex@gmail.com>
> > Reported-by: Craig Robson <craig@zhatt.com>
> > Fixes: 7aee9c52d7ac ("tpm: tpm1: rewrite tpm1_get_random() using tpm_buf structure")
> > Cc: Laura Abbott <labbott@redhat.com>
> > Cc: Tomas Winkler <tomas.winkler@intel.com>
> > Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> > v3: fix never-succeed, limit checks to tpm cmd return (James, Jason)
> > v2: also fix tpm2 implementation (Jason Gunthorpe)
> > ---
> >  drivers/char/tpm/tpm1-cmd.c | 7 +++++--
> >  drivers/char/tpm/tpm2-cmd.c | 7 +++++--
> >  2 files changed, 10 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
> > index 85dcf2654d11..faacbe1ffa1a 100644
> > --- a/drivers/char/tpm/tpm1-cmd.c
> > +++ b/drivers/char/tpm/tpm1-cmd.c
> > @@ -510,7 +510,7 @@ struct tpm1_get_random_out {
> >   *
> >   * Return:
> >   * *  number of bytes read
> > - * * -errno or a TPM return code otherwise
> > + * * -errno (positive TPM return codes are masked to -EIO)
> >   */
> >  int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
> >  {
> > @@ -531,8 +531,11 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
> >  
> >  		rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
> >  				      "attempting get random");
> > -		if (rc)
> > +		if (rc) {
> > +			if (rc > 0)
> > +				rc = -EIO;
> >  			goto out;
> > +		}
> >  
> >  		out = (struct tpm1_get_random_out *)&buf.data[TPM_HEADER_SIZE];
> >  
> > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> > index e74c5b7b64bf..8ffa6af61580 100644
> > --- a/drivers/char/tpm/tpm2-cmd.c
> > +++ b/drivers/char/tpm/tpm2-cmd.c
> > @@ -301,7 +301,7 @@ struct tpm2_get_random_out {
> >   *
> >   * Return:
> >   *   size of the buffer on success,
> > - *   -errno otherwise
> > + *   -errno otherwise ((positive TPM return codes are masked to -EIO)
> >   */
> >  int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
> >  {
> > @@ -328,8 +328,11 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
> >  				       offsetof(struct tpm2_get_random_out,
> >  						buffer),
> >  				       "attempting get random");
> > -		if (err)
> > +		if (err) {
> > +			if (err > 0)
> > +				err = -EIO;
> >  			goto out;
> > +		}
> >  
> >  		out = (struct tpm2_get_random_out *)
> >  			&buf.data[TPM_HEADER_SIZE];
> > -- 
> > 2.17.1
> > 
> > 
> > -- 
> > Kees Cook
> 
> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

Applied to my master branch. Jason, Tomas, do you want me to add
reviewed-by's?

/Jarkko

RE: [PATCH v3] tpm: Actually fail on TPM errors during "get random"

[Winkler, Tomas]

> On Tue, Apr 02, 2019 at 02:46:25AM +0300, Jarkko Sakkinen wrote:
> > On Mon, Apr 01, 2019 at 12:06:07PM -0700, Kees Cook wrote:
> > > A "get random" may fail with a TPM error, but those codes were
> > > returned as-is to the caller, which assumed the result was the
> > > number of bytes that had been written to the target buffer, which
> > > could lead to a kernel heap memory exposure and over-read.
> > >
> > > This fixes tpm1_get_random() to mask positive TPM errors into -EIO,
> > > as before.
> > >
> > > [   18.092103] tpm tpm0: A TPM error (379) occurred attempting get
> random
> > > [   18.092106] usercopy: Kernel memory exposure attempt detected from
> SLUB object 'kmalloc-64' (offset 0, size 379)!
> > >
> > > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1650989
> > > Reported-by: Phil Baker <baker1tex@gmail.com>
> > > Reported-by: Craig Robson <craig@zhatt.com>
> > > Fixes: 7aee9c52d7ac ("tpm: tpm1: rewrite tpm1_get_random() using
> > > tpm_buf structure")
> > > Cc: Laura Abbott <labbott@redhat.com>
> > > Cc: Tomas Winkler <tomas.winkler@intel.com>
> > > Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > ---
> > > v3: fix never-succeed, limit checks to tpm cmd return (James, Jason)
> > > v2: also fix tpm2 implementation (Jason Gunthorpe)
> > > ---
> > >  drivers/char/tpm/tpm1-cmd.c | 7 +++++--
> > > drivers/char/tpm/tpm2-cmd.c | 7 +++++--
> > >  2 files changed, 10 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/char/tpm/tpm1-cmd.c
> > > b/drivers/char/tpm/tpm1-cmd.c index 85dcf2654d11..faacbe1ffa1a
> > > 100644
> > > --- a/drivers/char/tpm/tpm1-cmd.c
> > > +++ b/drivers/char/tpm/tpm1-cmd.c
> > > @@ -510,7 +510,7 @@ struct tpm1_get_random_out {
> > >   *
> > >   * Return:
> > >   * *  number of bytes read
> > > - * * -errno or a TPM return code otherwise
> > > + * * -errno (positive TPM return codes are masked to -EIO)
> > >   */
> > >  int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)  {
> > > @@ -531,8 +531,11 @@ int tpm1_get_random(struct tpm_chip *chip, u8
> > > *dest, size_t max)
> > >
> > >  		rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
> > >  				      "attempting get random");
> > > -		if (rc)
> > > +		if (rc) {
> > > +			if (rc > 0)
> > > +				rc = -EIO;
> > >  			goto out;
> > > +		}
> > >
> > >  		out = (struct tpm1_get_random_out
> *)&buf.data[TPM_HEADER_SIZE];
> > >
> > > diff --git a/drivers/char/tpm/tpm2-cmd.c
> > > b/drivers/char/tpm/tpm2-cmd.c index e74c5b7b64bf..8ffa6af61580
> > > 100644
> > > --- a/drivers/char/tpm/tpm2-cmd.c
> > > +++ b/drivers/char/tpm/tpm2-cmd.c
> > > @@ -301,7 +301,7 @@ struct tpm2_get_random_out {
> > >   *
> > >   * Return:
> > >   *   size of the buffer on success,
> > > - *   -errno otherwise
> > > + *   -errno otherwise ((positive TPM return codes are masked to -EIO)
> > >   */
> > >  int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)  {
> > > @@ -328,8 +328,11 @@ int tpm2_get_random(struct tpm_chip *chip, u8
> *dest, size_t max)
> > >  				       offsetof(struct tpm2_get_random_out,
> > >  						buffer),
> > >  				       "attempting get random");
> > > -		if (err)
> > > +		if (err) {
> > > +			if (err > 0)
> > > +				err = -EIO;
> > >  			goto out;
> > > +		}
> > >
> > >  		out = (struct tpm2_get_random_out *)
> > >  			&buf.data[TPM_HEADER_SIZE];
> > > --
> > > 2.17.1
> > >
> > >
> > > --
> > > Kees Cook
> >
> > Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> 
> Applied to my master branch. Jason, Tomas, do you want me to add reviewed-
> by's?
Sure, it fixes my patch.

> /Jarkko

Re: [PATCH v3] tpm: Actually fail on TPM errors during "get random"

[Jarkko Sakkinen]

On Tue, Apr 02, 2019 at 07:13:52PM +0000, Winkler, Tomas wrote:
> 
> 
> > On Tue, Apr 02, 2019 at 02:46:25AM +0300, Jarkko Sakkinen wrote:
> > > On Mon, Apr 01, 2019 at 12:06:07PM -0700, Kees Cook wrote:
> > > > A "get random" may fail with a TPM error, but those codes were
> > > > returned as-is to the caller, which assumed the result was the
> > > > number of bytes that had been written to the target buffer, which
> > > > could lead to a kernel heap memory exposure and over-read.
> > > >
> > > > This fixes tpm1_get_random() to mask positive TPM errors into -EIO,
> > > > as before.
> > > >
> > > > [   18.092103] tpm tpm0: A TPM error (379) occurred attempting get
> > random
> > > > [   18.092106] usercopy: Kernel memory exposure attempt detected from
> > SLUB object 'kmalloc-64' (offset 0, size 379)!
> > > >
> > > > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1650989
> > > > Reported-by: Phil Baker <baker1tex@gmail.com>
> > > > Reported-by: Craig Robson <craig@zhatt.com>
> > > > Fixes: 7aee9c52d7ac ("tpm: tpm1: rewrite tpm1_get_random() using
> > > > tpm_buf structure")
> > > > Cc: Laura Abbott <labbott@redhat.com>
> > > > Cc: Tomas Winkler <tomas.winkler@intel.com>
> > > > Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> > > > Cc: stable@vger.kernel.org
> > > > Signed-off-by: Kees Cook <keescook@chromium.org>
> > > > ---
> > > > v3: fix never-succeed, limit checks to tpm cmd return (James, Jason)
> > > > v2: also fix tpm2 implementation (Jason Gunthorpe)
> > > > ---
> > > >  drivers/char/tpm/tpm1-cmd.c | 7 +++++--
> > > > drivers/char/tpm/tpm2-cmd.c | 7 +++++--
> > > >  2 files changed, 10 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/drivers/char/tpm/tpm1-cmd.c
> > > > b/drivers/char/tpm/tpm1-cmd.c index 85dcf2654d11..faacbe1ffa1a
> > > > 100644
> > > > --- a/drivers/char/tpm/tpm1-cmd.c
> > > > +++ b/drivers/char/tpm/tpm1-cmd.c
> > > > @@ -510,7 +510,7 @@ struct tpm1_get_random_out {
> > > >   *
> > > >   * Return:
> > > >   * *  number of bytes read
> > > > - * * -errno or a TPM return code otherwise
> > > > + * * -errno (positive TPM return codes are masked to -EIO)
> > > >   */
> > > >  int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)  {
> > > > @@ -531,8 +531,11 @@ int tpm1_get_random(struct tpm_chip *chip, u8
> > > > *dest, size_t max)
> > > >
> > > >  		rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
> > > >  				      "attempting get random");
> > > > -		if (rc)
> > > > +		if (rc) {
> > > > +			if (rc > 0)
> > > > +				rc = -EIO;
> > > >  			goto out;
> > > > +		}
> > > >
> > > >  		out = (struct tpm1_get_random_out
> > *)&buf.data[TPM_HEADER_SIZE];
> > > >
> > > > diff --git a/drivers/char/tpm/tpm2-cmd.c
> > > > b/drivers/char/tpm/tpm2-cmd.c index e74c5b7b64bf..8ffa6af61580
> > > > 100644
> > > > --- a/drivers/char/tpm/tpm2-cmd.c
> > > > +++ b/drivers/char/tpm/tpm2-cmd.c
> > > > @@ -301,7 +301,7 @@ struct tpm2_get_random_out {
> > > >   *
> > > >   * Return:
> > > >   *   size of the buffer on success,
> > > > - *   -errno otherwise
> > > > + *   -errno otherwise ((positive TPM return codes are masked to -EIO)
> > > >   */
> > > >  int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)  {
> > > > @@ -328,8 +328,11 @@ int tpm2_get_random(struct tpm_chip *chip, u8
> > *dest, size_t max)
> > > >  				       offsetof(struct tpm2_get_random_out,
> > > >  						buffer),
> > > >  				       "attempting get random");
> > > > -		if (err)
> > > > +		if (err) {
> > > > +			if (err > 0)
> > > > +				err = -EIO;
> > > >  			goto out;
> > > > +		}
> > > >
> > > >  		out = (struct tpm2_get_random_out *)
> > > >  			&buf.data[TPM_HEADER_SIZE];
> > > > --
> > > > 2.17.1
> > > >
> > > >
> > > > --
> > > > Kees Cook
> > >
> > > Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
> > 
> > Applied to my master branch. Jason, Tomas, do you want me to add reviewed-
> > by's?
> Sure, it fixes my patch.

Great, I'll add it. Thank you. Just want to be explicit with these
things as I consider them as if I was asking a signature from someone
:-)

/Jarkko

Re: [PATCH v3] tpm: Actually fail on TPM errors during "get random"

[Laura Abbott]

On 4/3/19 1:52 PM, Jarkko Sakkinen wrote:
> On Tue, Apr 02, 2019 at 07:13:52PM +0000, Winkler, Tomas wrote:
>>
>>
>>> On Tue, Apr 02, 2019 at 02:46:25AM +0300, Jarkko Sakkinen wrote:
>>>> On Mon, Apr 01, 2019 at 12:06:07PM -0700, Kees Cook wrote:
>>>>> A "get random" may fail with a TPM error, but those codes were
>>>>> returned as-is to the caller, which assumed the result was the
>>>>> number of bytes that had been written to the target buffer, which
>>>>> could lead to a kernel heap memory exposure and over-read.
>>>>>
>>>>> This fixes tpm1_get_random() to mask positive TPM errors into -EIO,
>>>>> as before.
>>>>>
>>>>> [   18.092103] tpm tpm0: A TPM error (379) occurred attempting get
>>> random
>>>>> [   18.092106] usercopy: Kernel memory exposure attempt detected from
>>> SLUB object 'kmalloc-64' (offset 0, size 379)!
>>>>>
>>>>> Link: https://bugzilla.redhat.com/show_bug.cgi?id=1650989
>>>>> Reported-by: Phil Baker <baker1tex@gmail.com>
>>>>> Reported-by: Craig Robson <craig@zhatt.com>
>>>>> Fixes: 7aee9c52d7ac ("tpm: tpm1: rewrite tpm1_get_random() using
>>>>> tpm_buf structure")
>>>>> Cc: Laura Abbott <labbott@redhat.com>
>>>>> Cc: Tomas Winkler <tomas.winkler@intel.com>
>>>>> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
>>>>> Cc: stable@vger.kernel.org
>>>>> Signed-off-by: Kees Cook <keescook@chromium.org>
>>>>> ---
>>>>> v3: fix never-succeed, limit checks to tpm cmd return (James, Jason)
>>>>> v2: also fix tpm2 implementation (Jason Gunthorpe)
>>>>> ---
>>>>>   drivers/char/tpm/tpm1-cmd.c | 7 +++++--
>>>>> drivers/char/tpm/tpm2-cmd.c | 7 +++++--
>>>>>   2 files changed, 10 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/drivers/char/tpm/tpm1-cmd.c
>>>>> b/drivers/char/tpm/tpm1-cmd.c index 85dcf2654d11..faacbe1ffa1a
>>>>> 100644
>>>>> --- a/drivers/char/tpm/tpm1-cmd.c
>>>>> +++ b/drivers/char/tpm/tpm1-cmd.c
>>>>> @@ -510,7 +510,7 @@ struct tpm1_get_random_out {
>>>>>    *
>>>>>    * Return:
>>>>>    * *  number of bytes read
>>>>> - * * -errno or a TPM return code otherwise
>>>>> + * * -errno (positive TPM return codes are masked to -EIO)
>>>>>    */
>>>>>   int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)  {
>>>>> @@ -531,8 +531,11 @@ int tpm1_get_random(struct tpm_chip *chip, u8
>>>>> *dest, size_t max)
>>>>>
>>>>>   		rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
>>>>>   				      "attempting get random");
>>>>> -		if (rc)
>>>>> +		if (rc) {
>>>>> +			if (rc > 0)
>>>>> +				rc = -EIO;
>>>>>   			goto out;
>>>>> +		}
>>>>>
>>>>>   		out = (struct tpm1_get_random_out
>>> *)&buf.data[TPM_HEADER_SIZE];
>>>>>
>>>>> diff --git a/drivers/char/tpm/tpm2-cmd.c
>>>>> b/drivers/char/tpm/tpm2-cmd.c index e74c5b7b64bf..8ffa6af61580
>>>>> 100644
>>>>> --- a/drivers/char/tpm/tpm2-cmd.c
>>>>> +++ b/drivers/char/tpm/tpm2-cmd.c
>>>>> @@ -301,7 +301,7 @@ struct tpm2_get_random_out {
>>>>>    *
>>>>>    * Return:
>>>>>    *   size of the buffer on success,
>>>>> - *   -errno otherwise
>>>>> + *   -errno otherwise ((positive TPM return codes are masked to -EIO)
>>>>>    */
>>>>>   int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)  {
>>>>> @@ -328,8 +328,11 @@ int tpm2_get_random(struct tpm_chip *chip, u8
>>> *dest, size_t max)
>>>>>   				       offsetof(struct tpm2_get_random_out,
>>>>>   						buffer),
>>>>>   				       "attempting get random");
>>>>> -		if (err)
>>>>> +		if (err) {
>>>>> +			if (err > 0)
>>>>> +				err = -EIO;
>>>>>   			goto out;
>>>>> +		}
>>>>>
>>>>>   		out = (struct tpm2_get_random_out *)
>>>>>   			&buf.data[TPM_HEADER_SIZE];
>>>>> --
>>>>> 2.17.1
>>>>>
>>>>>
>>>>> --
>>>>> Kees Cook
>>>>
>>>> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
>>>
>>> Applied to my master branch. Jason, Tomas, do you want me to add reviewed-
>>> by's?
>> Sure, it fixes my patch.
> 
> Great, I'll add it. Thank you. Just want to be explicit with these
> things as I consider them as if I was asking a signature from someone
> :-)
> 
> /Jarkko
> 
Was this intended to go in for 5.2? I still don't see it in the tree.

Thanks,
Laura

Re: [PATCH v3] tpm: Actually fail on TPM errors during "get random"

[Jarkko Sakkinen]

On Tue, May 28, 2019 at 03:02:49PM -0400, Laura Abbott wrote:
> > Great, I'll add it. Thank you. Just want to be explicit with these
> > things as I consider them as if I was asking a signature from someone
> > :-)
> > 
> > /Jarkko
> > 
> Was this intended to go in for 5.2? I still don't see it in the tree.

Was intended but I failed to notice that I should start to send PRs
to Linus instead of security tree and was waiting for security tree
to be rebased. I'll include to the next PR.

/Jarkko