From: Pavel Begunkov <[email protected]>
To: Jens Axboe <[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 23:16:01 +0300 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
[-- Attachment #1.1: Type: text/plain, Size: 2158 bytes --]
On 28/01/2020 22:42, Jens Axboe wrote:
> On 1/28/20 11:04 AM, Jens Axboe wrote:
>> On 1/28/20 10:19 AM, Jens Axboe wrote:
>>> On 1/28/20 9:19 AM, Jens Axboe wrote:
>>>> On 1/28/20 9:17 AM, Stefan Metzmacher wrote:
>>> 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.
>>
>> Minor tweak to ensuring we do the right thing for async offload as well,
>> and it tests fine for me. Test case is:
>>
>> - Run as root
>> - Register personality for root
>> - create root only file
>> - check we can IORING_OP_OPENAT the file
>> - switch to user id test
>> - check we cannot IORING_OP_OPENAT the file
>> - check that we can open the file with IORING_OP_USE_CREDS linked
>
> 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.
>
To be honest, sounds pretty dangerous. Especially since somebody started talking
about stealing fds from a process, it could lead to a nasty loophole somehow.
E.g. root registers its credentials, passes io_uring it to non-privileged
children, and then some process steals the uring fd (though, it would need
priviledged mode for code-injection or else). Could we Cc here someone really
keen on security?
Stefan, could you please explain, how this 5 syscalls pattern from the first
email came in the first place? Just want to understand the case.
--
Pavel Begunkov
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]
next prev parent reply other threads:[~2020-01-28 20:16 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 [this message]
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