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Subject: Re: [PATCH] driver core: Fix use-after-free and double free on glue
 directory
To:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        Muchun Song <smuchun@gmail.com>
Cc:     rafael@kernel.org, linux-kernel <linux-kernel@vger.kernel.org>,
        zhaowuyun@wingtech.com, linux-arm-msm@vger.kernel.org
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From:   Gaurav Kohli <gkohli@codeaurora.org>
Message-ID: <6d755534-714b-5d04-3280-b27fd8a1df1b@codeaurora.org>
Date:   Fri, 10 May 2019 09:01:14 +0530
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Thanks for the comment, will check the patch and update.

Regards
Gaurav

On 5/10/2019 4:52 AM, Benjamin Herrenschmidt wrote:
> On Thu, 2019-05-09 at 20:08 +0530, Gaurav Kohli wrote:
>> Hi ,
>>
>> Last patch will serialize the addition of child to parent directory,
>> won't it affect performance.
> 
> I doubt this is a significant issue, and there's already a global lock
> taken once or twice in that path, the fix is purely to make sure that
> the some locked section is used both for the lookup and the addition as
> the bug comes from the window in between those two operations allowing
> the object to be removed after it was "found".
> 
> Cheers,
> Ben.
>   
>>
>> Regards
>> Gaurav
>>
>> On 5/4/2019 9:04 PM, Greg KH wrote:
>>> On Sat, May 04, 2019 at 10:47:07PM +0800, Muchun Song wrote:
>>>> Benjamin Herrenschmidt <benh@kernel.crashing.org> 于2019年5月2日周四
>>>> 下午2:25写道：
>>>>
>>>>>>> The basic idea yes, the whole bool *locked is horrid
>>>>>>> though.
>>>>>>> Wouldn't it
>>>>>>> work to have a get_device_parent_locked that always returns
>>>>>>> with
>>>>>>> the mutex held,
>>>>>>> or just move the mutex to the caller or something simpler
>>>>>>> like this
>>>>>>> ?
>>>>>>>
>>>>>>
>>>>>> Greg and Rafael, do you have any suggestions for this? Or you
>>>>>> also
>>>>>> agree with Ben?
>>>>>
>>>>> Ping guys ? This is worth fixing...
>>>>
>>>> I also agree with you. But Greg and Rafael seem to be high
>>>> latency right now.
>>>
>>> It's in my list of patches to get to, sorry, hopefully will dig out
>>> of
>>> that next week with the buffer that the merge window provides me.
>>>
>>> thanks,
>>>
>>> greg k-h
>>>
>>
>>
> 

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