linux-kernel - Re: [PATCH 3/3] f2fs: prevent waiter encountering incorrect discard states

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Message-ID: <61dcdb40-0e30-fbc7-8bc3-19326c4eada4@huawei.com>
Date:   Wed, 5 Apr 2017 18:25:49 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>
Subject: Re: [PATCH 3/3] f2fs: prevent waiter encountering incorrect discard
 states

On 2017/4/4 1:40, Jaegeuk Kim wrote:
> On 04/01, Chao Yu wrote:
>> Ping,
>>
>> Any problem here?
>>
>> Thanks,
>>
>> On 2017/3/28 9:17, Chao Yu wrote:
>>> On 2017/3/28 7:56, Jaegeuk Kim wrote:
>>>> On 03/27, Chao Yu wrote:
>>>>> In f2fs_submit_discard_endio, we will wake up waiter before setting
>>>>> discard command states, so waiter may use incorrect states. Change
>>>>> the order between complete() and states setting to fix this issue.
>>>>>
>>>>> Signed-off-by: Chao Yu <yuchao0@...wei.com>
>>>>> ---
>>>>>  fs/f2fs/segment.c | 2 +-
>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>> index 57a81f9c8c14..9f9542c9fe47 100644
>>>>> --- a/fs/f2fs/segment.c
>>>>> +++ b/fs/f2fs/segment.c
>>>>> @@ -717,9 +717,9 @@ static void f2fs_submit_discard_endio(struct bio *bio)
>>>>>  {
>>>>>  	struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private;
>>>>>  
>>>>> -	complete(&dc->wait);
>>>>>  	dc->error = bio->bi_error;
>>>>>  	dc->state = D_DONE;
>>>>> +	complete(&dc->wait);
>>>>
>>>> If we set D_DONE first, the object can be released by __remove_discard_cmd()?
> 
> What I mean was about use-after-free.

I updated the patch, could you help to review it?

Thanks,

> 
> Thanks,
> 
>>>
>>> Yes, I think so.
>>>
>>> Thanks,
>>>
>>>>
>>>> Thanks,
>>>>
>>>>>  	bio_put(bio);
>>>>>  }
>>>>>  
>>>>> -- 
>>>>> 2.8.2.295.g3f1c1d0
>>>>
>>>> .
>>>>
> 
> .
>