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SubjectRe: [GIT PULL] New TPM driver, hwrng driver and fixes
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>> +                     /* err can be positive if it came from the TPM itself,
>> + * so return a negative value here instead. */
>> + err = -EFAULT;
>
> -EFAULT is definitely wrong (that means a bad pointer was passed), you
> can use -EIO instead.
>
> However, I would suggest:
>
> err = total ? total : -EIO;

This is fine w/ me...

> ... so you report the number of bytes successfully received if we got
> any. However, since you *also* do that on the retry line,
>
>> + goto out_err;
>> + }
>> +
>> + recd = be32_to_cpu(tpm_cmd.params.getrandom_out.rng_data_len);
>> + memcpy(dest, tpm_cmd.params.getrandom_out.rng_data, recd);
>> +
>> + dest += recd;
>> + total += recd;
>> + num_bytes -= recd;
>> + } while (retries-- && total < max);
>> +
>> + err = total;
>
> Should we return something other than 0 if we run out of retries here, too?

Ugh, I was hoping to avoid this kind of complexity.

> Perhaps we should just do the same "err = total ? total : -EIO;" here
> and the above statement can just turn into a break;.

Yeah, this seems like the right thing to do.

>> - ret = my_get_random(hash, SHA1_DIGEST_SIZE);
>> + ret = tpm_get_random(TPM_ANY_NUM, hash, SHA1_DIGEST_SIZE);
>> if (ret < 0)
>> return ret;
>
> You are still not checking the return values correctly!

Dave, can you weigh in on these individual cases? In some cases
like capping a pcr I think using uninitialized stack data could be
better than failing...

Kent

> This needs to be something like:
>
> ret = tpm_get_random(TPM_ANY_NUM, hash, SHA1_DIGEST_SIZE);
> if (ret != SHA1_DIGEST_SIZE)
> return -EIO; /* Or whatever is appropriate here */
>
>
> -hpa
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--
IBM LTC Security


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