netdev - Re: [Patch net] smc: move unhash as early as possible in smc

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Date:   Mon, 7 Jan 2019 17:45:49 +0100
From:   Ursula Braun <ubraun@...ux.ibm.com>
To:     David Miller <davem@...emloft.net>, xiyou.wangcong@...il.com
Cc:     netdev@...r.kernel.org, mhjungk@...il.com,
        syzbot+fbd1e5476e4c94c7b34e@...kaller.appspotmail.com
Subject: Re: [Patch net] smc: move unhash as early as possible in
 smc_release()



On 01/07/2019 04:12 PM, David Miller wrote:
> From: Cong Wang <xiyou.wangcong@...il.com>
> Date: Sat,  5 Jan 2019 23:45:26 -0800
> 
>> In smc_release() we release smc->clcsock before unhash the smc
>> sock, but a parallel smc_diag_dump() may be still reading
>> smc->clcsock, therefore this could cause a use-after-free as
>> reported by syzbot.
>>
>> Reported-and-tested-by: syzbot+fbd1e5476e4c94c7b34e@...kaller.appspotmail.com
>> Fixes: 51f1de79ad8e ("net/smc: replace sock_put worker by socket refcounting")
>> Cc: Ursula Braun <ubraun@...ux.ibm.com>
>> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> 
> We have two patches messing around in here, seeming to deal with release
> visibility and ordering problems in two different ways.
> 
> https://patchwork.ozlabs.org/patch/1020608/
> https://patchwork.ozlabs.org/patch/1021044/
> 
> Reported-by: syzbot+0bf2e01269f1274b4b03@...kaller.appspotmail.com
> Reported-by: syzbot+e3132895630f957306bc@...kaller.appspotmail.com
> 

The patches from Myungho Jung fix a closing problem for listening SMC-sockets.
The patch by Cong Wang fixes a closing problem for SMC-sockets when smc_diag_dump()
is running in parallel. Both are valuable in my eyes.