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Subject[PATCH v2 1/2] tpm: Fix buffer access in tpm2_get_tpm_pt()
Date
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: stable@vger.kernel.org
Signed-off-by: Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@infineon.com>
---
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
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