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SubjectRe: [PATCH v3 1/2] tpm_tis_core: add optional max xfer size check
On Wed, Jul 27, 2016 at 08:49:56PM -0700, Andrey Pronin wrote:
> If tpm reports a bigger burstcnt than allowed by the physical protocol,
> set burstcnt to the max allowed value.
>
> In practice, seen in case of xfer issues (e.g. in spi interface case,
> lost header causing flow control issues and wrong values returned on read
> from TPM_STS). Without catching, causes the physical layer to reject xfer.
>
> Signed-off-by: Andrey Pronin <apronin@chromium.org>

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

I don't have hardware to test this. Someone should validate that it
does not break anything. Christophe, are you able to do this?

/Jarkko

> ---
> drivers/char/tpm/tpm_tis_core.c | 9 ++++++++-
> drivers/char/tpm/tpm_tis_core.h | 1 +
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index f22caf8..7c4fa0c 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -168,8 +168,15 @@ static int get_burstcount(struct tpm_chip *chip)
> return rc;
>
> burstcnt = (value >> 8) & 0xFFFF;
> - if (burstcnt)
> + if (burstcnt) {
> + if (priv->phy_ops->max_xfer_size &&
> + (burstcnt > priv->phy_ops->max_xfer_size)) {
> + dev_warn(&chip->dev,
> + "Bad burstcnt read: %d\n", burstcnt);
> + burstcnt = priv->phy_ops->max_xfer_size;
> + }
> return burstcnt;
> + }
> msleep(TPM_TIMEOUT);
> } while (time_before(jiffies, stop));
> return -EBUSY;
> diff --git a/drivers/char/tpm/tpm_tis_core.h b/drivers/char/tpm/tpm_tis_core.h
> index 9191aab..58e8b14 100644
> --- a/drivers/char/tpm/tpm_tis_core.h
> +++ b/drivers/char/tpm/tpm_tis_core.h
> @@ -102,6 +102,7 @@ struct tpm_tis_phy_ops {
> int (*read16)(struct tpm_tis_data *data, u32 addr, u16 *result);
> int (*read32)(struct tpm_tis_data *data, u32 addr, u32 *result);
> int (*write32)(struct tpm_tis_data *data, u32 addr, u32 src);
> + u16 max_xfer_size;
> };
>
> static inline int tpm_tis_read_bytes(struct tpm_tis_data *data, u32 addr,
> --
> 2.6.6
>

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