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

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Message-ID: <CAM_iQpXqL+=Qz0kB88O_m4xYDmr_pZBis1erKXox3gP4x9iNvA@mail.gmail.com>
Date:   Mon, 7 Jan 2019 11:25:12 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        mhjungk@...il.com,
        syzbot <syzbot+fbd1e5476e4c94c7b34e@...kaller.appspotmail.com>,
        Ursula Braun <ubraun@...ux.ibm.com>
Subject: Re: [Patch net] smc: move unhash as early as possible in smc_release()

On Mon, Jan 7, 2019 at 7:12 AM David Miller <davem@...emloft.net> 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

Isn't Myungho's patch already merged as commit 78abe3d0dfad? :)

So I believe the syzbot reported this bug on top of that commit.

Thanks.