From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>,
Stefan Metzmacher <[email protected]>
Cc: io-uring <[email protected]>,
Linux API Mailing List <[email protected]>
Subject: Re: IORING_REGISTER_CREDS[_UPDATE]() and credfd_create()?
Date: Tue, 28 Jan 2020 17:18:47 -0700 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 1/28/20 5:15 PM, Jens Axboe wrote:
> On 1/28/20 5:10 PM, Pavel Begunkov wrote:
>> On 29/01/2020 02:51, Jens Axboe wrote:
>>> On 1/28/20 4:40 PM, Jens Axboe wrote:
>>>> 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.
>>>
>>
>> Hmm, it seems it leaks it unconditionally, as it grabs in a ref in
>> override_creds().
>>
>>> I think this may have gotten fixed with the later addition posted today?
>>> I'll double check. But for the newer stuff, we put it for both cases
>>> when the request is freed.
>>
>> Yeah, maybe. I got tangled trying to verify both at once and decided to start
>> with the old one.
>>
>>
>>>>> 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.
>>
>> Apparently, you're faster :)
>>
>>>
>>> Testing this now, what a braino.
>>>
>>> diff --git a/fs/io-wq.c b/fs/io-wq.c
>>> index ee49e8852d39..8fbbadf04cc3 100644
>>> --- a/fs/io-wq.c
>>> +++ b/fs/io-wq.c
>>> @@ -56,7 +56,8 @@ struct io_worker {
>>>
>>> struct rcu_head rcu;
>>> struct mm_struct *mm;
>>> - const struct cred *creds;
>>> + const struct cred *cur_creds;
>>> + const struct cred *saved_creds;
>>> struct files_struct *restore_files;
>>> };
>>>
>>> @@ -135,9 +136,9 @@ static bool __io_worker_unuse(struct io_wqe *wqe, struct io_worker *worker)
>>> {
>>> bool dropped_lock = false;
>>>
>>> - if (worker->creds) {
>>> - revert_creds(worker->creds);
>>> - worker->creds = NULL;
>>> + if (worker->saved_creds) {
>>> + revert_creds(worker->saved_creds);
>>> + worker->cur_creds = worker->saved_creds = NULL;
>>> }
>>>
>>> if (current->files != worker->restore_files) {
>>> @@ -424,10 +425,11 @@ static void io_wq_switch_mm(struct io_worker *worker, struct io_wq_work *work)
>>> static void io_wq_switch_creds(struct io_worker *worker,
>>> struct io_wq_work *work)
>>> {
>>> - if (worker->creds)
>>> - revert_creds(worker->creds);
>>> + if (worker->saved_creds)
>>> + revert_creds(worker->saved_creds);
>>>
>>> - worker->creds = override_creds(work->creds);
>>> + worker->saved_creds = override_creds(work->creds);
>>> + worker->cur_creds = work->creds;
>>> }
>>
>> How about as follows? rever_creds() is a bit heavier than put_creds().
>>
>> static void io_wq_switch_creds(struct io_worker *worker,
>> struct io_wq_work *work)
>> {
>> const struct cred *old_creds = override_creds(work->creds);
>>
>> if (worker->saved_creds)
>> put_cred(old_creds);
>> else
>> worker->saved_creds = old;
>> worker->cur_creds = work->creds;
>> }
>
> Looks good to me, I'll fold.
Actually, it doesn't clear current->cred then, which seems a bit..
unfortunate. Could be a source of issues.
--
Jens Axboe
next prev parent reply other threads:[~2020-01-29 0:18 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-28 10:18 IORING_REGISTER_CREDS[_UPDATE]() and credfd_create()? Stefan Metzmacher
2020-01-28 16:10 ` Jens Axboe
2020-01-28 16:17 ` Stefan Metzmacher
2020-01-28 16:19 ` Jens Axboe
2020-01-28 17:19 ` Jens Axboe
2020-01-28 18:04 ` Jens Axboe
2020-01-28 19:42 ` Jens Axboe
2020-01-28 20:16 ` Pavel Begunkov
2020-01-28 20:19 ` Jens Axboe
2020-01-28 20:50 ` Pavel Begunkov
2020-01-28 20:56 ` Jens Axboe
2020-01-28 21:25 ` Christian Brauner
2020-01-28 22:38 ` Pavel Begunkov
2020-01-28 23:36 ` Pavel Begunkov
2020-01-28 23:40 ` Jens Axboe
2020-01-28 23:51 ` Jens Axboe
2020-01-29 0:10 ` Pavel Begunkov
2020-01-29 0:15 ` Jens Axboe
2020-01-29 0:18 ` Jens Axboe [this message]
2020-01-29 0:20 ` Jens Axboe
2020-01-29 0:21 ` Pavel Begunkov
2020-01-29 0:24 ` Jens Axboe
2020-01-29 0:54 ` Jens Axboe
2020-01-29 10:17 ` Pavel Begunkov
2020-01-29 13:11 ` Stefan Metzmacher
2020-01-29 13:41 ` Pavel Begunkov
2020-01-29 13:56 ` Stefan Metzmacher
2020-01-29 14:23 ` Pavel Begunkov
2020-01-29 14:27 ` Stefan Metzmacher
2020-01-29 14:34 ` Pavel Begunkov
2020-01-29 17:34 ` Jens Axboe
2020-01-29 17:42 ` Jens Axboe
2020-01-29 20:09 ` Stefan Metzmacher
2020-01-29 20:48 ` Jens Axboe
2020-01-29 17:46 ` Pavel Begunkov
2020-01-29 14:59 ` Jann Horn
2020-01-29 17:34 ` Jens Axboe
2020-01-30 1:08 ` Jens Axboe
2020-01-30 2:20 ` Jens Axboe
2020-01-30 3:18 ` Jens Axboe
2020-01-30 6:53 ` Stefan Metzmacher
2020-01-30 10:11 ` Jann Horn
2020-01-30 10:26 ` Christian Brauner
2020-01-30 14:11 ` Jens Axboe
2020-01-30 14:47 ` Stefan Metzmacher
2020-01-30 15:34 ` Jens Axboe
2020-01-30 15:13 ` Christian Brauner
2020-01-30 15:29 ` Jens Axboe
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