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From: Stefan Metzmacher <[email protected]>
To: Jens Axboe <[email protected]>, [email protected]
Cc: [email protected], [email protected]
Subject: Re: [PATCH 3/6] io_uring: add support for IORING_OP_OPENAT
Date: Thu, 9 Jan 2020 00:03:45 +0100	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>


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Am 08.01.20 um 23:53 schrieb Jens Axboe:
> On 1/8/20 10:04 AM, Stefan Metzmacher wrote:
>> Am 08.01.20 um 17:40 schrieb Jens Axboe:
>>> On 1/8/20 9:32 AM, Stefan Metzmacher wrote:
>>>> Am 08.01.20 um 17:20 schrieb Jens Axboe:
>>>>> On 1/8/20 6:05 AM, Stefan Metzmacher wrote:
>>>>>> Hi Jens,
>>>>>>
>>>>>>> This works just like openat(2), except it can be performed async. For
>>>>>>> the normal case of a non-blocking path lookup this will complete
>>>>>>> inline. If we have to do IO to perform the open, it'll be done from
>>>>>>> async context.
>>>>>>
>>>>>> Did you already thought about the credentials being used for the async
>>>>>> open? The application could call setuid() and similar calls to change
>>>>>> the credentials of the userspace process/threads. In order for
>>>>>> applications like samba to use this async openat, it would be required
>>>>>> to specify the credentials for each open, as we have to multiplex
>>>>>> requests from multiple user sessions in one process.
>>>>>>
>>>>>> This applies to non-fd based syscall. Also for an async connect
>>>>>> to a unix domain socket.
>>>>>>
>>>>>> Do you have comments on this?
>>>>>
>>>>> The open works like any of the other commands, it inherits the
>>>>> credentials that the ring was setup with. Same with the memory context,
>>>>> file table, etc. There's currently no way to have multiple personalities
>>>>> within a single ring.
>>>>
>>>> Ah, it's user = get_uid(current_user()); and ctx->user = user in
>>>> io_uring_create(), right?
>>>
>>> That's just for the accounting, it's the:
>>>
>>> ctx->creds = get_current_cred();
>>
>> Ok, I just looked at an old checkout.
>>
>> In kernel-dk-block/for-5.6/io_uring-vfs I see this only used in
>> the async processing. Does a non-blocking openat also use ctx->creds?
> 
> There's basically two sets here - one set is in the ring, and the other
> is the identity that the async thread (briefly) assumes if we have to go
> async. Right now they are the same thing, and hence we don't need to
> play any tricks off the system call submitting SQEs to assume any other
> identity than the one we have.

I see two cases using it io_sq_thread() and
io_wq_create()->io_worker_handle_work() call override_creds().

But aren't non-blocking syscall executed in the context of the thread
calling io_uring_enter()->io_submit_sqes()?
In only see some magic around ctx->sqo_mm for that case, but ctx->creds
doesn't seem to be used in that case. And my design would require that.

metze


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  reply	other threads:[~2020-01-08 23:03 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-07 17:00 [PATCHSET v2 0/6] io_uring: add support for open/close Jens Axboe
2020-01-07 17:00 ` [PATCH 1/6] fs: add namei support for doing a non-blocking path lookup Jens Axboe
2020-01-25 13:15   ` Jeff Layton
2020-01-07 17:00 ` [PATCH 2/6] fs: make build_open_flags() available internally Jens Axboe
2020-01-07 17:00 ` [PATCH 3/6] io_uring: add support for IORING_OP_OPENAT Jens Axboe
2020-01-08 13:05   ` Stefan Metzmacher
2020-01-08 16:20     ` Jens Axboe
2020-01-08 16:32       ` Stefan Metzmacher
2020-01-08 16:40         ` Jens Axboe
2020-01-08 17:04           ` Stefan Metzmacher
2020-01-08 22:53             ` Jens Axboe
2020-01-08 23:03               ` Stefan Metzmacher [this message]
2020-01-08 23:05                 ` Jens Axboe
2020-01-08 23:11                   ` Stefan Metzmacher
2020-01-08 23:22                     ` Jens Axboe
2020-01-09 10:40                       ` Stefan Metzmacher
2020-01-09 21:31                         ` Jens Axboe
2020-01-16 22:42                           ` Stefan Metzmacher
2020-01-17  0:16                             ` Jens Axboe
2020-01-07 17:00 ` [PATCH 4/6] fs: move filp_close() outside of __close_fd_get_file() Jens Axboe
2020-01-07 17:00 ` [PATCH 5/6] io-wq: add support for uncancellable work Jens Axboe
2020-01-07 17:00 ` [PATCH 6/6] io_uring: add support for IORING_OP_CLOSE Jens Axboe
2020-01-08 21:17 ` [PATCHSET v2 0/6] io_uring: add support for open/close Stefan Metzmacher
2020-01-08 22:57   ` Jens Axboe
2020-01-08 23:05     ` Stefan Metzmacher
2020-01-09  1:02       ` Jens Axboe
2020-01-09  2:03         ` Jens Axboe
2020-01-16 22:50           ` Stefan Metzmacher
2020-01-17  0:18             ` Jens Axboe
2020-01-20 12:15               ` Stefan Metzmacher
2020-01-20 13:04                 ` Pavel Begunkov
2020-01-17  0:44             ` Colin Walters
2020-01-17  0:51               ` Jens Axboe
2020-01-17  9:32               ` Pavel Begunkov
2020-01-17 15:21                 ` Jens Axboe
2020-01-17 22:27                   ` Pavel Begunkov
2020-01-17 22:36                     ` Jens Axboe

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