linux-kernel - Re: [PATCH] KEYS: trusted: allow module init if TPM is inactive or deactivated

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Message-ID: <20190711194811.rfsohbfc3a7carpa@linux.intel.com>
Date:   Thu, 11 Jul 2019 22:48:11 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>
Cc:     jejb@...ux.ibm.com, zohar@...ux.ibm.com, jgg@...pe.ca,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-kernel@...r.kernel.org, crazyt2019+lml@...il.com,
        tyhicks@...onical.com, nayna@...ux.vnet.ibm.com,
        silviu.vlasceanu@...wei.com
Subject: Re: [PATCH] KEYS: trusted: allow module init if TPM is inactive or
 deactivated

On Fri, Jul 05, 2019 at 06:37:35PM +0200, Roberto Sassu wrote:
> Commit c78719203fc6 ("KEYS: trusted: allow trusted.ko to initialize w/o a
> TPM") allows the trusted module to be loaded even a TPM is not found to
> avoid module dependency problems.
> 
> Unfortunately, this does not completely solve the issue, as there could be
> a case where a TPM is found but is not functional (the TPM commands return
> an error). Specifically, after the tpm_chip structure is returned by
> tpm_default_chip() in init_trusted(), the execution terminates after
> init_digests() returns -EFAULT (due to the fact that tpm_get_random()
> returns a positive value, but less than TPM_MAX_DIGEST_SIZE).
> 
> This patch fixes the issue by ignoring the TPM_ERR_DEACTIVATED and
> TPM_ERR_DISABLED errors.

Why allow trusted module to initialize if TPM is not functional?

Also:

err = tpm_transmit_cmd(chip, &buf,
		       offsetof(struct tpm2_get_random_out,
				buffer),
		       "attempting get random");
if (err) {
	if (err > 0)
		err = -EIO;
	goto out;
}

/Jarkko