2022-05-14 01:09:12

by Stefan Mahnke-Hartmann

Subject: [PATCH v2 1/2] tpm: Fix buffer access in tpm2_get_tpm_pt()

Under certain conditions uninitialized memory will be accessed.
As described by TCG Trusted Platform Module Library Specification,
rev. 1.59 (Part 3: Commands), if a TPM2_GetCapability is received,
requesting a capability, the TPM in field upgrade mode may return a
zero length list.
Check the property count in tpm2_get_tpm_pt().

Fixes: 2ab3241161b3 ("tpm: migrate tpm2_get_tpm_pt() to use struct tpm_buf")
Cc: [email protected]
Signed-off-by: Stefan Mahnke-Hartmann <[email protected]>
---
Changelog:
* v2:
* Add inline comment to indicate the root cause to may access unitilized
memory.
* Change 'field upgrade mode' to lower case.

drivers/char/tpm/tpm2-cmd.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 4704fa553098..04a3e23a4afc 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -400,7 +400,16 @@ ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id, u32 *value,
if (!rc) {
out = (struct tpm2_get_cap_out *)
&buf.data[TPM_HEADER_SIZE];
- *value = be32_to_cpu(out->value);
+ /*
+ * To prevent failing boot up of some systems, Infineon TPM2.0
+ * returns SUCCESS on TPM2_Startup in field upgrade mode. Also
+ * the TPM2_Getcapability command returns a zero length list
+ * in field upgrade mode.
+ */
+ if (be32_to_cpu(out->property_cnt) > 0)
+ *value = be32_to_cpu(out->value);
+ else
+ rc = -ENODATA;
}
tpm_buf_destroy(&buf);
return rc;
--
2.25.1

2022-05-17 02:36:59

by Jarkko Sakkinen

Subject: Re: [PATCH v2 1/2] tpm: Fix buffer access in tpm2_get_tpm_pt()

On Fri, May 13, 2022 at 03:41:51PM +0200, Stefan Mahnke-Hartmann wrote:
> Under certain conditions uninitialized memory will be accessed.
> As described by TCG Trusted Platform Module Library Specification,
> rev. 1.59 (Part 3: Commands), if a TPM2_GetCapability is received,
> requesting a capability, the TPM in field upgrade mode may return a
> zero length list.
> Check the property count in tpm2_get_tpm_pt().
>
> Fixes: 2ab3241161b3 ("tpm: migrate tpm2_get_tpm_pt() to use struct tpm_buf")
> Cc: [email protected]
> Signed-off-by: Stefan Mahnke-Hartmann <[email protected]>
> ---
> Changelog:
> * v2:
> * Add inline comment to indicate the root cause to may access unitilized
> memory.
> * Change 'field upgrade mode' to lower case.
>
> drivers/char/tpm/tpm2-cmd.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 4704fa553098..04a3e23a4afc 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -400,7 +400,16 @@ ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id, u32 *value,
> if (!rc) {
> out = (struct tpm2_get_cap_out *)
> &buf.data[TPM_HEADER_SIZE];
> - *value = be32_to_cpu(out->value);
> + /*
> + * To prevent failing boot up of some systems, Infineon TPM2.0
> + * returns SUCCESS on TPM2_Startup in field upgrade mode. Also
> + * the TPM2_Getcapability command returns a zero length list
> + * in field upgrade mode.
> + */
> + if (be32_to_cpu(out->property_cnt) > 0)
> + *value = be32_to_cpu(out->value);
> + else
> + rc = -ENODATA;
> }
> tpm_buf_destroy(&buf);
> return rc;
> --
> 2.25.1
>

Reviewed-by: Jarkko Sakkinen <[email protected]>

BR, Jarkko