From: Jens Axboe <[email protected]>
To: Stefan Metzmacher <[email protected]>
Cc: io-uring <[email protected]>,
Linux API Mailing List <[email protected]>,
Pavel Begunkov <[email protected]>
Subject: Re: IORING_REGISTER_CREDS[_UPDATE]() and credfd_create()?
Date: Tue, 28 Jan 2020 10:19:51 -0700 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
On 1/28/20 9:19 AM, Jens Axboe wrote:
> On 1/28/20 9:17 AM, Stefan Metzmacher wrote:
>> Am 28.01.20 um 17:10 schrieb Jens Axboe:
>>> On 1/28/20 3:18 AM, Stefan Metzmacher wrote:
>>>> Hi Jens,
>>>>
>>>> now that we have IORING_FEAT_CUR_PERSONALITY...
>>>>
>>>> How can we optimize the fileserver case now, in order to avoid the
>>>> overhead of always calling 5 syscalls before io_uring_enter()?:
>>>>
>>>> /* gain root again */
>>>> setresuid(-1,0,-1); setresgid(-1,0,-1)
>>>> /* impersonate the user with groups */
>>>> setgroups(num, grps); setresgid(-1,gid,-1); setresuid(-1,uid,-1);
>>>> /* trigger the operation */
>>>> io_uring_enter();
>>>>
>>>> I guess some kind of IORING_REGISTER_CREDS[_UPDATE] would be
>>>> good, together with a IOSQE_FIXED_CREDS in order to specify
>>>> credentials per operation.
>>>>
>>>> Or we make it much more generic and introduce a credsfd_create()
>>>> syscall in order to get an fd for a credential handle, maybe
>>>> together with another syscall to activate the credentials of
>>>> the current thread (or let a write to the fd trigger the activation
>>>> in order to avoid an additional syscall number).
>>>>
>>>> Having just an fd would allow IORING_REGISTER_CREDS[_UPDATE]
>>>> to be just an array of int values instead of a more complex
>>>> structure to define the credentials.
>>>
>>> I'd rather avoid having to add more infrastructure for this, even if
>>> credsfd_create() would be nifty.
>>>
>>> With that in mind, something like:
>>>
>>> - Application does IORING_REGISTER_CREDS, which returns some index
>>>
>>> - Add a IORING_OP_USE_CREDS opcode, which sets the creds associated
>>> with dependent commands
>>> - Actual request is linked to the IORING_OP_USE_CREDS command, any
>>> link off IORING_OP_USE_CREDS will use those credentials
>>
>> Using links for this sounds ok.
>
> Great! I'll try and hack this up and see how it turns out.
>
>>> - IORING_UNREGISTER_CREDS removes the registered creds
>>>
>>> Just throwing that out there, definitely willing to entertain other
>>> methods that make sense for this. Trying to avoid needing to put this
>>> information in the SQE itself, hence the idea to use a chain of links
>>> for it.
>>>
>>> The downside is that we'll need to maintain an array of key -> creds,
>>> but that's probably not a big deal.
>>>
>>> What do you think?
>>
>> So IORING_REGISTER_CREDS would be a simple operation that just takes a
>> snapshot of the current_cred() and returns an id that can be passed to
>> IORING_OP_USE_CREDS or IORING_UNREGISTER_CREDS?
>
> Right, you would not pass in any arguments, it'd have to be run from the
> personality you wish to register. It simply returns an integer, which is
> a key to use for IORING_OP_USE_CREDS, or at the end for
> IORING_UNREGISTER_CREDS when you no longer wish to use this personality.
>
>>> Ideally I'd like to get this done for 5.6 even if we
>>> are a bit late, so you'll have everything you need with that release.
>>
>> That would be great!
>
> Crossing fingers...
OK, so here are two patches for testing:
https://git.kernel.dk/cgit/linux-block/log/?h=for-5.6/io_uring-vfs-creds
#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'll try and write a test case for this just to see if it actually works,
so far it's totally untested.
Adding Pavel to the CC.
--
Jens Axboe
next prev parent reply other threads:[~2020-01-28 17:19 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 [this message]
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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox