From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Jerry Snitselaar <jsnitsel@redhat.com>
Cc: linux-integrity@vger.kernel.org, Mimi Zohar <zohar@linux.ibm.com>,
Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Subject: Re: [PATCH v2 1/1] tpm: add sysfs exports for all banks of PCR registers
Date: Tue, 21 Jul 2020 17:39:45 -0700 [thread overview]
Message-ID: <1595378385.3575.31.camel@HansenPartnership.com> (raw)
In-Reply-To: <877duwl8n9.fsf@redhat.com>
On Tue, 2020-07-21 at 17:02 -0700, Jerry Snitselaar wrote:
> James Bottomley @ 2020-07-21 16:37 MST:
>
> > On Tue, 2020-07-21 at 16:16 -0700, Jerry Snitselaar wrote:
> > > James Bottomley @ 2020-07-21 08:56 MST:
> >
> > [...]
> > > > + /*
> > > > + * This will only trigger if someone has added an
> > > > additional
> > > > + * hash to the tpm_algorithms enum without
> > > > incrementing
> > > > + * TPM_MAX_HASHES. This has to be a BUG_ON because
> > > > under
> > > > this
> > > > + * condition, the chip->groups array will overflow
> > > > corrupting
> > > > + * the chips structure.
> > > > + */
> > > > + BUG_ON(chip->groups_cnt > TPM_MAX_HASHES);
> > >
> > > Should this check be 3 + TPM_MAX_HASHES like below?
> >
> > No, because at this point only a single additional group has been
> > addedin addition to the hashes groups. The first line of
> > tpm_sysfs_add_device is
> >
> > WARN_ON(chip->groups_cnt != 0);
> >
> > And then we add the unnamed group. This loop over the banks
> > follows it, so chip->groups_cnt should be nr_banks_allocated by the
> > end (it's the index, which is one fewer than the number of entries
> > in chip->groups[]). We have a problem if nr_banks_allocated >
> > TPM_MAX_HASHES
> >
> > which is what the BUG_ON checks.
> >
> > James
>
> If the chip supported all 5 listed cases wouldn't groups_cnt be 6 at
> this point?
Actually, yes, I think it would be because it's pointing at the next
free index not the current one. So it should be BUG_ON (chip-
>groups_cnt > TPM_MAX_HASHES + 1)
James
next prev parent reply other threads:[~2020-07-22 0:39 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-21 15:56 [PATCH v2 0/1] add sysfs exports for TPM 2 PCR registers James Bottomley
2020-07-21 15:56 ` [PATCH v2 1/1] tpm: add sysfs exports for all banks of " James Bottomley
2020-07-21 16:57 ` Mimi Zohar
2020-07-21 23:16 ` Jerry Snitselaar
2020-07-21 23:37 ` James Bottomley
2020-07-22 0:02 ` Jerry Snitselaar
2020-07-22 0:39 ` James Bottomley [this message]
2020-07-22 0:51 ` Jerry Snitselaar
2020-07-22 15:29 ` James Bottomley
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