lkml.org 
[lkml]   [2021]   [Nov]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH v19 3/5] tpm: tpm_tis: Verify TPM_STS register is valid after locality request
    From
    Date
    On Thu, 2021-11-04 at 16:02 +0200, amirmizi6@gmail.com wrote:
    > From: Amir Mizinski <amirmizi6@gmail.com>
    >
    > An invalid TPM_STS value could be used when the following two events occur:
    > TPM does not update TPM_STS register after a locality request (TPM_STS
    > Initial value = 0xFF), and a TPM_STS register read occurs in the
    > tpm_tis_status(chip) function call.
    >
    > In probe_itpm(), a call to tpm_tis_send_data() function is made after a
    > request_locality() call, and the condition
    > ("if ((status & TPM_STS_COMMAND_READY) == 0)") is checked. At this moment
    > if the status value is 0xFF, then it is considered, wrongly, in “ready”
    > state (by checking only one bit). However, at this moment the TPM is, in
    > fact, in "Idle" state and remains in "Idle" state because
    > "tpm_tis_ready(chip);" was not executed.
    > Waiting for the condition TPM_STS.tpmGo == 0, will ensure that the TPM
    > status register has the correct value.

    You should use imperative form in commit message, e.g. "Wait for TPM_STS.tpmGo
    to reset to zero, ...".

    >
    > Suggested-by: Benoit Houyere <benoit.houyere@st.com>
    > Signed-off-by: Amir Mizinski <amirmizi6@gmail.com>
    > ---
    >  drivers/char/tpm/tpm_tis_core.c | 6 +++++-
    >  1 file changed, 5 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
    > index 6ff8b44..770685a 100644
    > --- a/drivers/char/tpm/tpm_tis_core.c
    > +++ b/drivers/char/tpm/tpm_tis_core.c
    > @@ -177,8 +177,12 @@ static int request_locality(struct tpm_chip *chip, int l)
    >         } else {
    >                 /* wait for burstcount */
    >                 do {
    > -                       if (check_locality(chip, l))
    > +                       if (check_locality(chip, l)) {
    > +                               if (tpm_tis_wait_for_stat(chip, TPM_STS_GO, 0, chip->timeout_c,
    > +                                                         &priv->int_queue, false) < 0)

    You would need to explain this with an inline comment.

    > +                                       return -ETIME;
    >                                 return l;
    > +                       }
    >                         tpm_msleep(TPM_TIMEOUT);
    >                 } while (time_before(jiffies, stop));
    >         }


    /Jarkko

    \
     
     \ /
      Last update: 2021-11-17 09:12    [W:3.176 / U:0.792 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site