From: Pavel Begunkov <asml.silence@gmail.com>
To: Jens Axboe <axboe@kernel.dk>,
io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] io_uring: fix deferred req iovec leak
Date: Fri, 7 Feb 2020 00:03:52 +0300 [thread overview]
Message-ID: <e45f5f9d-a8f8-01d8-1658-c0744662f8ed@gmail.com> (raw)
In-Reply-To: <2095dbc7-88fb-9d4f-78a5-8577dda09a92@kernel.dk>
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On 06/02/2020 23:58, Jens Axboe wrote:
>>
>> 1. submit a read, which need defer.
>>
>> 2. io_req_defer() allocates ->io and goes io_req_defer_prep() -> io_read_prep().
>> Let #vecs > UIO_FASTIOV, so the prep() in the presence of ->io will allocate iovec.
>> Note: that work.func is left io_wq_submit_work
>>
>> 3. At some point @io_wq calls io_wq_submit_work() -> io_issue_sqe() -> io_read(),
>>
>> 4. actual reading succeeds, and it's coming to finalisation and the following
>> code in particular.
>>
>> if (!io_wq_current_is_worker())
>> kfree(iovec);
>>
>> 5. Because we're in io_wq, the cleanup will not be performed, even though we're
>> returning with success. And that's a leak.
>>
>> Do you see anything wrong with it?
>
> That's my bad, I didn't read the subject fully, this is specific to
> a deferred request. Patch looks good to me, and it cleans it up too
> which is always a nice win!
>
Great we're agree. Though, it's not only about defer, it's just one example.
The another one is a non-head request, for which io_submit_sqe() allocates ->io,
+ REQ_F_FORCE_ASYNC.
--
Pavel Begunkov
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next prev parent reply other threads:[~2020-02-06 21:04 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-06 16:51 [PATCH] io_uring: fix deferred req iovec leak Pavel Begunkov
2020-02-06 17:04 ` Pavel Begunkov
2020-02-06 17:16 ` Pavel Begunkov
2020-02-06 19:56 ` Jens Axboe
2020-02-06 20:00 ` Pavel Begunkov
2020-02-06 20:16 ` Jens Axboe
2020-02-06 20:39 ` Pavel Begunkov
2020-02-06 20:58 ` Jens Axboe
2020-02-06 21:03 ` Pavel Begunkov [this message]
2020-02-06 21:00 ` Pavel Begunkov
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