[PATCH] tpm: add buffer access validation in tpm2_get_pcr_allocation()

Nayna Jain
2017-01-27T15:27:47Z

This patch add validation in tpm2_get_pcr_allocation to avoid
access beyond response buffer length.

Suggested-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Signed-off-by: Nayna Jain <nayna@linux.vnet.ibm.com>
---
drivers/char/tpm/tpm2-cmd.c | 28 +++++++++++++++++++++++-----
1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 4aad84c..02c1ea7 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -1008,9 +1008,13 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
struct tpm2_pcr_selection pcr_selection;
struct tpm_buf buf;
void *marker;
- unsigned int count = 0;
+ void *end;
+ void *pcr_select_offset;
+ unsigned int count;
+ u32 sizeof_pcr_selection;
+ u32 resp_len;
int rc;
- int i;
+ int i = 0;

rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
if (rc)
@@ -1034,15 +1038,29 @@ static ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
}

marker = &buf.data[TPM_HEADER_SIZE + 9];
+
+ resp_len = be32_to_cpup((__be32 *)&buf.data[2]);
+ end = &buf.data[resp_len];
+
for (i = 0; i < count; i++) {
+ pcr_select_offset = marker +
+ offsetof(struct tpm2_pcr_selection, size_of_select);
+ if (pcr_select_offset >= end) {
+ rc = -EFAULT;
+ break;
+ }
+
memcpy(&pcr_selection, marker, sizeof(pcr_selection));
chip->active_banks[i] = be16_to_cpu(pcr_selection.hash_alg);
- marker = marker + sizeof(struct tpm2_pcr_selection);
+ sizeof_pcr_selection = sizeof(pcr_selection.hash_alg) +
+ sizeof(pcr_selection.size_of_select) +
+ sizeof(u8) * pcr_selection.size_of_select;
+ marker = marker + sizeof_pcr_selection;
}

out:
- if (count < ARRAY_SIZE(chip->active_banks))
- chip->active_banks[count] = TPM2_ALG_ERROR;
+ if (i < ARRAY_SIZE(chip->active_banks))
+ chip->active_banks[i] = TPM2_ALG_ERROR;

tpm_buf_destroy(&buf);

--
2.5.0