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From: Jens Axboe <axboe@kernel.dk>
To: Stefan Metzmacher <metze@samba.org>, io-uring@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk
Subject: Re: [PATCH 3/6] io_uring: add support for IORING_OP_OPENAT
Date: Thu, 16 Jan 2020 17:16:43 -0700
Message-ID: <38c19d02-ff10-c4a3-3d25-c59530ada19e@kernel.dk> (raw)
In-Reply-To: <7a91c0ee-ee1c-bec4-98fd-a25664839423@samba.org>

On 1/16/20 3:42 PM, Stefan Metzmacher wrote:
>>> I'm not sure if current->mm is needed, I just added it for completeness
>>> and as hint that io_op_defs[req->opcode].needs_mm is there and a
>>> needs_creds could also be added (if it helps with performance)
>>>
>>> Is it possible to trigger a change of current->mm from userspace?
>>>
>>> An IORING_REGISTER_CREDS would only be useful if it's possible to
>>> register a set of credentials and then use per io_uring_sqe credentials.
>>> That would also be fine for me, but I'm not sure it's needed for now.
>>
>> I think it'd be a cleaner way of doing the same thing as your patch
>> does. It seems a little odd to do this by default (having the ring
>> change personalities depending on who's using it), but from an opt-in
>> point of view, I think it makes more sense.
>>
>> That would make the IORING_REGISTER_ call something like
>> IORING_REGISTER_ADOPT_OWNER or something like that, meaning that the
>> ring would just assume the identify of the task that's calling
>> io_uring_enter().
>>
>> Note that this also has to be passed through to the io-wq handler, as
>> the mappings there are currently static as well.
> 
> What's the next step here?

Not sure, need to find some time to work on this!

> I think the current state is a security problem!
> 
> The inline execution either needs to change the creds temporary
> or io_uring_enter() needs a general check that the current creds match
> the creds of the ring and return -EPERM or something similar.

Hmm, if you transfer the fd to someone else, you also give them access
to your credentials etc. We could make that -EPERM, if the owner of the
ring isn't the one invoking the submit. But that doesn't really help the
SQPOLL case, which simply consumes SQE entries. There can be no checking
there.

-- 
Jens Axboe


  reply index

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
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 [this message]
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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