From: Jens Axboe <axboe@kernel.dk>
To: Pavel Begunkov <asml.silence@gmail.com>, io-uring@vger.kernel.org
Subject: Re: [RFC][BUG] io_uring: fix work corruption for poll_add
Date: Thu, 23 Jul 2020 12:19:47 -0600 [thread overview]
Message-ID: <ecb56297-ec6d-de6f-a619-6d19549d2272@kernel.dk> (raw)
In-Reply-To: <e42e74bd-6220-c933-fce1-4005c3c7b2dd@gmail.com>
On 7/23/20 12:15 PM, Pavel Begunkov wrote:
> On 23/07/2020 21:12, Pavel Begunkov wrote:
>> poll_add can have req->work initialised, which will be overwritten in
>> __io_arm_poll_handler() because of the union. Luckily, hash_node is
>> zeroed in the end, so the damage is limited to lost put for work.creds,
>> and probably corrupted work.list.
>>
>> That's the easiest and really dirty fix, which rearranges members in the
>> union, arm_poll*() modifies and zeroes only work.files and work.mm,
>> which are never taken for poll add.
>> note: io_kiocb is exactly 4 cachelines now.
>
> Please, tell me if anybody has a good lean solution, because I'm a bit
> too tired at the moment to fix it properly.
> BTW, that's for 5.8, for-5.9 it should be done differently because of
> io_kiocb compaction.
Do you have a test case that leaks the reference?
--
Jens Axboe
next prev parent reply other threads:[~2020-07-23 18:19 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 18:12 [RFC][BUG] io_uring: fix work corruption for poll_add Pavel Begunkov
2020-07-23 18:15 ` Pavel Begunkov
2020-07-23 18:19 ` Jens Axboe [this message]
2020-07-23 19:10 ` Pavel Begunkov
2020-07-23 22:16 ` Jens Axboe
2020-07-23 22:24 ` Jens Axboe
2020-07-24 12:46 ` Pavel Begunkov
2020-07-24 12:52 ` Pavel Begunkov
2020-07-24 14:12 ` Jens Axboe
2020-07-24 14:23 ` Pavel Begunkov
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