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SubjectRe: [PATCH] security/keys/trusted: Allow operation without hardware TPM
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On 3/21/2019 2:54 PM, Jarkko Sakkinen wrote:
> On Mon, Mar 18, 2019 at 04:45:13PM -0700, Dan Williams wrote:
>> Rather than fail initialization of the trusted.ko module, arrange for
>> the module to load, but rely on trusted_instantiate() to fail
>> trusted-key operations.
>>
>> Fixes: 240730437deb ("KEYS: trusted: explicitly use tpm_chip structure...")
>> Cc: Roberto Sassu <roberto.sassu@huawei.com>
>> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
>> Cc: James Bottomley <jejb@linux.ibm.com>
>> Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
>> Cc: Mimi Zohar <zohar@linux.ibm.com>
>> Cc: David Howells <dhowells@redhat.com>
>> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
>
> It should check for chip in each function that uses TPM now that
> the code does not rely on default chip. Otherwise, the semantics
> are kind of inconsistent.

If no other TPM function can be used before a successful key
instantiate, checking for a chip only in trusted_instantiate() seems
sufficient. Then, the same chip will be used by all TPM functions until
module unloading, since we incremented the reference count.

I would suggest to move the tpm_default_chip() and init_digests() calls
to trusted_instantiate() to restore the old behavior of init_trusted().

trusted_instantiate() should look like:
---
if (!chip) {
chip = tpm_default_chip();
if (!chip)
return -ENODEV;
}

if (!digests) {
ret = init_digests();
if (ret < 0)
return ret;
}
---

Roberto


> /Jarkko
>

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