Re: [PATCH] tpm: fixes uninitialized allocated banks for IBM vtpm driver

[Nayna]

On 07/05/2019 10:13 AM, Stefan Berger wrote:
> On 7/3/19 11:32 PM, Nayna Jain wrote:
> > The nr_allocated_banks and allocated banks are initialized as part of
> > tpm_chip_register. Currently, this is done as part of auto startup
> > function. However, some drivers, like the ibm vtpm driver, do not run
> > auto startup during initialization. This results in uninitialized memory
> > issue and causes a kernel panic during boot.
> >
> > This patch moves the pcr allocation outside the auto startup function
> > into tpm_chip_register. This ensures that allocated banks are 
> > initialized
> > in any case.
> >
> > Fixes: 879b589210a9 ("tpm: retrieve digest size of unknown algorithms 
> > with
> > PCR read")
> > Signed-off-by: Nayna Jain <nayna@xxxxxxxxxxxxx>
> > ---
> > Â drivers/char/tpm/tpm-chip.c | 37 +++++++++++++++++++++++++++++++++++++
> > Â drivers/char/tpm/tpm.hÂÂÂÂÂ |Â 1 +
> > Â drivers/char/tpm/tpm1-cmd.c | 12 ------------
> > Â drivers/char/tpm/tpm2-cmd.c |Â 6 +-----
> > Â 4 files changed, 39 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index 8804c9e916fd..958508bb8379 100644
> > --- a/drivers/char/tpm/tpm-chip.c
> > +++ b/drivers/char/tpm/tpm-chip.c
> > @@ -550,6 +550,39 @@ static int tpm_add_hwrng(struct tpm_chip *chip)
> > ÂÂÂÂÂ return hwrng_register(&chip->hwrng);
> > Â }
> >
> > +/*
> > + * tpm_pcr_allocation() - initializes the chip allocated banks for PCRs
> > + */
> > +static int tpm_pcr_allocation(struct tpm_chip *chip)
> > +{
> > +ÂÂÂ int rc = 0;
> > +
> > +ÂÂÂ if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> > +ÂÂÂÂÂÂÂ rc = tpm2_get_pcr_allocation(chip);
> > +ÂÂÂÂÂÂÂ if (rc)
> > +ÂÂÂÂÂÂÂÂÂÂÂ goto out;
> > +ÂÂÂ }
> > +
> > +ÂÂÂ /* Initialize TPM 1.2 */
> > +ÂÂÂ chip->allocated_banks = kcalloc(1, sizeof(*chip->allocated_banks),
> > +ÂÂÂÂÂÂÂÂÂÂÂ GFP_KERNEL);
> > +ÂÂÂ if (!chip->allocated_banks) {
> > +ÂÂÂÂÂÂÂ rc = -ENOMEM;
> > +ÂÂÂÂÂÂÂ goto out;
> > +ÂÂÂ }
> > +
> > +ÂÂÂ chip->allocated_banks[0].alg_id = TPM_ALG_SHA1;
> > +ÂÂÂ chip->allocated_banks[0].digest_size = 
> > hash_digest_size[HASH_ALGO_SHA1];
> > +ÂÂÂ chip->allocated_banks[0].crypto_id = HASH_ALGO_SHA1;
> > +ÂÂÂ chip->nr_allocated_banks = 1;
> > +
> > +ÂÂÂ return 0;
> > +out:
> > +ÂÂÂ if (rc < 0)
> > +ÂÂÂÂÂÂÂ rc = -ENODEV;
>
>
> The old code where you lifted this from said:
>
> out:
> ÂÂÂ if (rc > 0)
> ÂÂÂ ÂÂÂ rc = -ENODEV;
> ÂÂÂ return rc;
>
> It would not overwrite -ENOMEM with -ENODEV but yours does.
>
> I think the correct fix would be to use:
>
> if (rc > 0)
>
> ÂÂÂ rc = -ENODEV;

Yes. I think I misread it. Thanks Stefan. Will fix this..


> > +ÂÂÂ return rc;
> > +}
> > +
> > Â /*
> > ÂÂ * tpm_chip_register() - create a character device for the TPM chip
> > ÂÂ * @chip: TPM chip to use.
> > @@ -573,6 +606,10 @@ int tpm_chip_register(struct tpm_chip *chip)
> > ÂÂÂÂÂ if (rc)
> > ÂÂÂÂÂÂÂÂÂ return rc;
>
> Above this is tpm_chip_stop(chip) because (afaik) none of the 
> following function calls in tpm_chip_register() needed the TPM, but 
> now with tpm_pcr_allocation() you will need to send a command to the 
> TPM. So I would say you should move the tpm_chip_stop() into the error 
> branch visible above and also after the tpm_pcr_allocation().
>
>
> > +ÂÂÂ rc = tpm_pcr_allocation(chip);
> tpm_chip_stop(chip);

I am not sure of the purpose of tpm_stop_chip(), so I have left it as it 
is. Jarkko, what do you think about the change ?

Thanks & Regards,
ÂÂÂÂÂÂÂÂ - Nayna