linux-kernel - Re: [PATCH 4/6] usbip: fix stub_dev usbip_sockfd

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Message-ID: <7b9465aa-213e-a513-d033-12c048df15d6@i-love.sakura.ne.jp>
Date:   Wed, 10 Mar 2021 08:40:20 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Shuah Khan <skhan@...uxfoundation.org>, shuah@...nel.org,
        valentina.manea.m@...il.com, gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6] usbip: fix stub_dev usbip_sockfd_store() races
 leading to gpf

On 2021/03/10 4:50, Shuah Khan wrote:
> On 3/9/21 4:04 AM, Tetsuo Handa wrote:
>> On 2021/03/09 1:27, Shuah Khan wrote:
>>> Yes. We might need synchronization between events, threads, and shutdown
>>> in usbip_host side and in connection polling and threads in vhci.
>>>
>>> I am also looking at the shutdown sequences closely as well since the
>>> local state is referenced without usbip_device lock in these paths.
>>>
>>> I am approaching these problems as peeling the onion an expression so
>>> we can limit the changes and take a spot fix approach. We have the
>>> goal to address these crashes and not introduce regressions.
>>
>> I think my [PATCH v4 01/12]-[PATCH v4 06/12] simplify your further changes
>> without introducing regressions. While ud->lock is held when checking ud->status,
>> current attach/detach code is racy about read/update of ud->status . I think we
>> can close race in attach/detach code via a simple usbip_event_mutex serialization.
>>
> 
> Do you mean patches 1,2,3,3,4,5,6?

Yes, my 1,2,3,4,5,6.

Since you think that usbip_prepare_threads() does not worth introducing, I'm fine with
replacing my 7,8,9,10,11,12 with your "[PATCH 0/6] usbip fixes to crashes found by syzbot".