Re: [PATCH] tpm: vtpm_proxy: Do not access host's event log

[Nayna <nayna-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

On 11/18/2016 12:03 AM, Jason Gunthorpe wrote:
> On Thu, Nov 17, 2016 at 01:25:54PM -0500, Stefan Berger wrote:
>>
>> In the case of x86, tpm_read_log_of() is a stub return -ENODEV, which in
>> turn fails the whole device:
>
> Somehow this got screwed up during the lengthy review. ENODEV is the
> right return from the leaf routines but the tests in tpm_eventlog di
> not get fixed:

Isn't the idea is that if event_log specific properties are not 
supported in ACPI/OF , then probe should continue except for 
ENOMEM/ENODEV error ?

Error conditions from read_log_acpi()/read_log_of():

        - rc =  EIO (Probe continue) -  TCPA is not supported/event log 
area empty/failed acpi_os_map_iomem/event log device tree properties not 
exist. This implies error log is not supported by the platform.
        - rc = ENOMEM (Probe fail) - event log is supported but kmalloc 
failed.
        - rc = ENODEV (Probe fail) -  represents device not supported.

I think because of assumption that if event log is not supported on 
ACPI, it might be OF platform and so do tpm_read_log_of(), the EIO error 
from tpm_read_log_acpi() is getting masked.

Please let me know if I am missing something.

>
>> http://git.infradead.org/users/jjs/linux-tpmdd.git/blob/4d388433e85f8257f5a9344a7acf6f499ba2b29e:/drivers/char/tpm/tpm_eventlog.h#l87
>
> Is wrong, should be:
>
> if (rc != -ENODEV)
>     return rc;

Did you mean this check in tpm_chip_register() ?

Thanks & Regards,
   - Nayna

>
> And the one in tpm_bios_log_setup should be
>
> if (rc != 0 && rc != -ENODEV)
>      return rc;
>
>> I think the OF log reading code will also need to check for chip->dev.parent
>> being NULL.
>
> Currect! Lets get that fixed too. :(
>
>> Further, I had the impression that the error unwinding following -ENODEV has
>> an issue related to sysfs.
>
> I don't follow this comment..
>
> Jason
>


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