Re: [PATCH] io_uring: fix mm use with IORING_OP_{READ,WRITE}

From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>,
	io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] io_uring: fix mm use with IORING_OP_{READ,WRITE}
Date: Wed, 5 Feb 2020 09:05:08 -0700	[thread overview]
Message-ID: <c6cc1e97-f306-e3f0-3f7b-9463fdbbc5a5@kernel.dk> (raw)
In-Reply-To: <d9a15d32-a20b-a20f-9ea4-3ac355c15bb2@gmail.com>

On 2/5/20 9:02 AM, Pavel Begunkov wrote:
> On 05/02/2020 18:54, Jens Axboe wrote:
>> On 2/5/20 8:46 AM, Pavel Begunkov wrote:
>>> IORING_OP_{READ,WRITE} need mm to access user buffers, hence
>>> req->has_user check should go for them as well. Move the corresponding
>>> imports past the check.
>>
>> I'd need to double check, but I think the has_user check should just go.
>> The import checks for access anyway, so we'll -EFAULT there if we
>> somehow messed up and didn't acquire the right mm.
>>
> It'd be even better. I have plans to remove it, but I was thinking from a
> different angle.

Let me just confirm it in practice, but it should be fine. Then we can just
kill it.

-- 
Jens Axboe