Re: IORING_REGISTER_CREDS[_UPDATE]() and credfd_create()?

Jens Axboe
2020-01-28T23:40:30Z

On 1/28/20 4:36 PM, Pavel Begunkov wrote:
> On 28/01/2020 22:42, Jens Axboe wrote:
>> I didn't like it becoming a bit too complicated, both in terms of
>> implementation and use. And the fact that we'd have to jump through
>> hoops to make this work for a full chain.
>>
>> So I punted and just added sqe->personality and IOSQE_PERSONALITY.
>> This makes it way easier to use. Same branch:
>>
>> https://git.kernel.dk/cgit/linux-block/log/?h=for-5.6/io_uring-vfs-creds
>>
>> I'd feel much better with this variant for 5.6.
>>
>
> Checked out ("don't use static creds/mm assignments")
>
> 1. do we miscount cred refs? We grab one in get_current_cred() for each async
> request, but if (worker->creds != work->creds) it will never be put.

Yeah I think you're right, that needs a bit of fixing up.

> 2. shouldn't worker->creds be named {old,saved,etc}_creds? It's set as
>
> worker->creds = override_creds(work->creds);
>
> Where override_creds() returns previous creds. And if so, then the following
> fast check looks strange:
>
> worker->creds != work->creds

Don't care too much about the naming, but the logic does appear off.
I'll take a look at both of these tonight, unless you beat me to it.

--
Jens Axboe