linux-kernel - Re: [BUG] io_uring: defer logic based on shared data

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Message-ID: <1e2c5f16-dd06-d184-ce5b-3f3d4f76eec2@kernel.dk>
Date:   Fri, 25 Oct 2019 10:21:41 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG] io_uring: defer logic based on shared data

On 10/25/19 10:09 AM, Jens Axboe wrote:
> On 10/25/19 10:03 AM, Jens Axboe wrote:
>> On 10/25/19 3:55 AM, Pavel Begunkov wrote:
>>> I found 2 problems with __io_sequence_defer().
>>>
>>> 1. it uses @sq_dropped, but doesn't consider @cq_overflow
>>> 2. @sq_dropped and @cq_overflow are write-shared with userspace, so
>>> it can be maliciously changed.
>>>
>>> see sent liburing test (test/defer *_hung()), which left an unkillable
>>> process for me
>>
>> OK, how about the below. I'll split this in two, as it's really two
>> separate fixes.
> 
> Patch 1:
> 
> http://git.kernel.dk/cgit/linux-block/commit/?h=for-linus&id=9a9a21d9cf65cb621cce4052a4527868a80009ad
> 
> and patch 2:
> 
> http://git.kernel.dk/cgit/linux-block/commit/?h=for-linus&id=ed348662f74c4f63537b3c188585e39cdea22713
> 
> Let me know what you think, and if/when I can add your reviewed/test-by
> to them.

Updated patch 2 as per the other discussion, here it is:

http://git.kernel.dk/cgit/linux-block/commit/?h=for-linus&id=b6c2c446c0fca0318dec904821bd11f52d2445d3


-- 
Jens Axboe