>
> If the TPM we're connecting to uses a static burst count, it will report a
> burst
> count of zero throughout the response read. However, get_burstcount assumes
> that a response of zero indicates that the TPM is not ready to receive more
> data. In this case, it returns a negative error code, which is passed on to
> tpm_tis_{write,read}_bytes as a u16, causing them to read/write far too many
> bytes.
>
> This patch checks for negative return codes and bails out from recv_data and
> tpm_tis_send_data.
>
> Fixes: 1107d065fdf1 (tpm_tis: Introduce intermediate layer for TPM access)
> Signed-off-by: Josh Zimmerman <jo...@google.com>
>
> ---
> Changelog v4:
> - Add short description to Fixes tag line.
> - Remove some unnecessary information in dev_err statements.
> Changelog v3:
> - Add signed-off-by.
> Changelog v2:
> - Fix typo (rc->burstcnt)
>
> ---
> drivers/char/tpm/tpm_tis_core.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index e3bf31b..0f2c233 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -186,6 +186,10 @@ static int recv_data(struct tpm_chip *chip, u8 *buf,
> size_t count)
> chip->timeout_c,
> &priv->read_queue, true) == 0) {
> burstcnt = min_t(int, get_burstcount(chip), count - size);
> + if (burstcnt < 0) {
It is much more readable to directly check get_burstcount return value, 'count
- size' is protected be above condition to not reach negative value.
burstcnt = get_burstcount(chip)
if (brustcnt < 0) ...
> + dev_err(&chip->dev, "Unable to read burstcount\n");
> + return burstcnt;
> + }
>
> rc = tpm_tis_read_bytes(priv, TPM_DATA_FIFO(priv->locality),
> burstcnt, buf + size);
> @@ -272,6 +276,11 @@ static int tpm_tis_send_data(struct tpm_chip *chip, u8
> *buf, size_t len)
>
> while (count < len - 1) {
> burstcnt = min_t(int, get_burstcount(chip), len - count - 1);
> + if (burstcnt < 0) {
Same here
> + dev_err(&chip->dev, "Unable to read burstcount\n");
> + rc = burstcnt;
> + goto out_err;
> + }
> rc = tpm_tis_write_bytes(priv, TPM_DATA_FIFO(priv->locality),
> burstcnt, buf + count);
> if (rc < 0)
> --
> 2.8.0.rc3.226.g39d4020
Thanks
Tomas
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