[PATCH v2 1/7] tpm: move length validation to tpm_transmit()

[Jarkko Sakkinen]

Check that the length matches the length reported by the response
header already in tpm_transmit() to improve validation.

Signed-off-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
---
 drivers/char/tpm/tpm-interface.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index bd2128e..708d356 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -343,6 +343,7 @@ EXPORT_SYMBOL_GPL(tpm_calc_ordinal_duration);
 ssize_t tpm_transmit(struct tpm_chip *chip, const u8 *buf, size_t bufsiz,
                     unsigned int flags)
 {
+       const struct tpm_output_header *header = (void *)buf;
        ssize_t rc;
        u32 count, ordinal;
        unsigned long stop;
@@ -406,9 +407,18 @@ ssize_t tpm_transmit(struct tpm_chip *chip, const u8 *buf, 
size_t bufsiz,
 
 out_recv:
        rc = chip->ops->recv(chip, (u8 *) buf, bufsiz);
-       if (rc < 0)
+       if (rc < 0) {
                dev_err(&chip->dev,
                        "tpm_transmit: tpm_recv: error %zd\n", rc);
+               goto out;
+       } else if (rc < TPM_HEADER_SIZE) {
+               rc = -EFAULT;
+               goto out;
+       }
+
+       if (rc != be32_to_cpu(header->length))
+               goto out;
+
 out:
        if (chip->dev.parent)
                pm_runtime_put_sync(chip->dev.parent);
@@ -438,19 +448,13 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, const 
void *buf,
                         size_t bufsiz, size_t min_rsp_body_length,
                         unsigned int flags, const char *desc)
 {
-       const struct tpm_output_header *header;
+       const struct tpm_output_header *header = buf;
        int err;
        ssize_t len;
 
        len = tpm_transmit(chip, (const u8 *)buf, bufsiz, flags);
        if (len <  0)
                return len;
-       else if (len < TPM_HEADER_SIZE)
-               return -EFAULT;
-
-       header = buf;
-       if (len != be32_to_cpu(header->length))
-               return -EFAULT;
 
        err = be32_to_cpu(header->return_code);
        if (err != 0 && desc)
-- 
2.9.3