netdev - Re: possible deadlock in skb_queue

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Date:   Tue, 3 Apr 2018 22:08:03 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>, Ingo Molnar <mingo@...nel.org>,
        syzbot <syzbot+6b495100f17ca8554ab9@...kaller.appspotmail.com>,
        David Miller <davem@...emloft.net>,
        David Herrmann <dh.herrmann@...il.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        David Windsor <dwindsor@...il.com>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        ishkamiel@...il.com, Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>, matthew@...systems.ca,
        Mateusz Jurczyk <mjurczyk@...gle.com>,
        netdev <netdev@...r.kernel.org>, syzkaller-bugs@...glegroups.com,
        Al Viro <viro@...iv.linux.org.uk>, xemul@...tuozzo.com
Subject: Re: possible deadlock in skb_queue_tail

On Tue, Apr 3, 2018 at 4:42 AM, Kirill Tkhai <ktkhai@...tuozzo.com> wrote:
> On 03.04.2018 14:25, Dmitry Vyukov wrote:
>> On Tue, Apr 3, 2018 at 11:50 AM, Kirill Tkhai <ktkhai@...tuozzo.com> wrote:
>>> sk_diag_dump_icons() dumps only sockets in TCP_LISTEN state.
>>> TCP_LISTEN state may be assigned in only place in net/unix/af_unix.c:
>>> it's unix_listen(). The function is applied to stream and seqpacket
>>> socket types.
>>>
>>> It can't be stream because of the second stack, and seqpacket also can't,
>>> as I don't think it's possible for gcc to inline unix_seqpacket_sendmsg()
>>> in the way, we don't see it in the stack.
>>>
>>> So, this is looks like false positive result for me.
>>>
>>> Kirill
>>
>> Do you mean that these &(&u->lock)->rlock/1 referenced in 2 stacks are
>> always different?
>
> In these 2 particular stacks they have to be different.

So actually my patch could fix this false positive? I thought it couldn't.
https://patchwork.ozlabs.org/patch/894342/