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Subject: Re: [BUG] io_uring: defer logic based on shared data
From:   Jens Axboe <axboe@kernel.dk>
To:     Pavel Begunkov <asml.silence@gmail.com>,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
References: <5badf1c0-9a7d-0950-2943-ff8db33e0929@gmail.com>
 <bfb58429-6abe-06f0-3fd8-14a0040cecf0@kernel.dk>
Message-ID: <dfd21591-5187-0a8b-cc55-cfe5d57dd471@kernel.dk>
Date:   Fri, 25 Oct 2019 10:09:41 -0600
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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.

-- 
Jens Axboe