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

[Jens Axboe <axboe@kernel.dk>]

On 1/29/20 7:59 AM, Jann Horn wrote:
> On Tue, Jan 28, 2020 at 8:42 PM Jens Axboe <axboe@kernel.dk> wrote:
>> On 1/28/20 11:04 AM, Jens Axboe wrote:
>>> On 1/28/20 10:19 AM, Jens Axboe wrote:
> [...]
>>>> #1 adds support for registering the personality of the invoking task,
>>>> and #2 adds support for IORING_OP_USE_CREDS. Right now it's limited to
>>>> just having one link, it doesn't support a chain of them.
> [...]
>> 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.
> 
> Some general feedback from an inspectability/debuggability perspective:
> 
> At some point, it might be nice if you could add a .show_fdinfo
> handler to the io_uring_fops that makes it possible to get a rough
> overview over the state of the uring by reading /proc/$pid/fdinfo/$fd,
> just like e.g. eventfd (see eventfd_show_fdinfo()). It might be
> helpful for debugging to be able to see information about the fixed
> files and buffers that have been registered. Same for the
> personalities; that information might also be useful when someone is
> trying to figure out what privileges a running process actually has.

Agree, that would be a very useful addition. I'll take a look at it.

-- 
Jens Axboe