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SubjectRe: [PATCH v2] KEYS: trusted: allow module init if TPM is inactive or deactivated
On 2019-08-02 17:07:33, 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
^ if

> avoid module dependency problems.
>
> However, trusted module initialization can still fail if the TPM is
> inactive or deactivated. This patch ignores tpm_get_random() errors in
> init_digests() and returns -EFAULT in pcrlock() if the TPM didn't return
> random data.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>

The code changes look correct to me.

Reviewed-by: Tyler Hicks <tyhicks@canonical.com>

For whoever takes this patch through their tree, I think that adding the
following Fixes tag would be useful (as well as cc'ing stable):

Fixes: 240730437deb ("KEYS: trusted: explicitly use tpm_chip structure...")

I think it is also worth leaving a short note, in the commit message,
for backporters that commit 782779b60faa ("tpm: Actually fail on TPM
errors during "get random"") should be included with any backports of
this patch.

Thanks!

Tyler

> ---
> security/keys/trusted.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/security/keys/trusted.c b/security/keys/trusted.c
> index 9a94672e7adc..34f04ffcf2e5 100644
> --- a/security/keys/trusted.c
> +++ b/security/keys/trusted.c
> @@ -389,6 +389,10 @@ static int pcrlock(const int pcrnum)
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> + /* This happens if the TPM didn't return random data */
> + if (!digests)
> + return -EFAULT;
> +
> return tpm_pcr_extend(chip, pcrnum, digests) ? -EINVAL : 0;
> }
>
> @@ -1233,10 +1237,8 @@ static int __init init_digests(void)
> int i;
>
> ret = tpm_get_random(chip, digest, TPM_MAX_DIGEST_SIZE);
> - if (ret < 0)
> - return ret;
> - if (ret < TPM_MAX_DIGEST_SIZE)
> - return -EFAULT;
> + if (ret < 0 || ret < TPM_MAX_DIGEST_SIZE)
> + return 0;
>
> digests = kcalloc(chip->nr_allocated_banks, sizeof(*digests),
> GFP_KERNEL);
> --
> 2.17.1
>

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