This patch protects against data corruption that could happen in the bus, by checking that that the digest size returned by the TPM during a PCR read matches the size of the algorithm passed to tpm2_pcr_read().
This check is performed after information about the PCR banks has been retrieved.
Signed-off-by: Roberto Sassu roberto.sassu@huawei.com Reviewed-by: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com Cc: stable@vger.kernel.org --- drivers/char/tpm/tpm2-cmd.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c index acaaab72ef2e..974465f04b78 100644 --- a/drivers/char/tpm/tpm2-cmd.c +++ b/drivers/char/tpm/tpm2-cmd.c @@ -179,15 +179,29 @@ struct tpm2_pcr_read_out { int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx, struct tpm_digest *digest_struct, u16 *digest_size_ptr) { + int i; int rc; struct tpm_buf buf; struct tpm2_pcr_read_out *out; u8 pcr_select[TPM2_PCR_SELECT_MIN] = {0}; u16 digest_size; + u16 expected_digest_size = 0;
if (pcr_idx >= TPM2_PLATFORM_PCR) return -EINVAL;
+ if (!digest_size_ptr) { + for (i = 0; i < chip->nr_allocated_banks && + chip->allocated_banks[i].alg_id != digest_struct->alg_id; + i++) + ; + + if (i == chip->nr_allocated_banks) + return -EINVAL; + + expected_digest_size = chip->allocated_banks[i].digest_size; + } + rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ); if (rc) return rc; @@ -207,7 +221,8 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE]; digest_size = be16_to_cpu(out->digest_size); - if (digest_size > sizeof(digest_struct->digest)) { + if (digest_size > sizeof(digest_struct->digest) || + (!digest_size_ptr && digest_size != expected_digest_size)) { rc = -EINVAL; goto out; }