Re: [tpmdd-devel] [PATCH] tpm: remove chip_num parameter from in-kernel API

[PrasannaKumar Muralidharan]

On 24 October 2017 at 21:41, Jason Gunthorpe
<jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, Oct 24, 2017 at 09:37:33PM +0530, PrasannaKumar Muralidharan wrote:
>> Hi Jason,
>>
>> On 24 October 2017 at 21:25, Jason Gunthorpe
>> <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote:
>> > On Tue, Oct 24, 2017 at 09:21:15PM +0530, PrasannaKumar Muralidharan wrote:
>> >
>> >> Please check the RFC [1]. It does use chip id. The rfc has issues and
>> >> has to be fixed but still there could be users of the API.
>> >>
>> >> 1. https://www.spinics.net/lists/linux-crypto/msg28282.html
>> >
>> > That patch isn't safe at all. You need to store a kref to th chip in
>> > the hwrng, not parse a string.
>>
>> The drivers/char/hw_random/tpm-rng.c module does not store the chip
>> reference so I guess the usage is safe.
>
> It is using the default TPM, it is always safe to use the default tpm.
>
>> The RFC is just a sample use case of the API.
>
> Well, a wrong example not to be emulated, and I think, further shows
> how Jarkko's direction is the right one.

I am wondering why it is wrong. Isn't the chip id valid till it is
unregistered? If so the rfc is correct. Please explain, may be I am
missing something.

Thanks,
PrasannaKumar