linux-kernel - Re: suspicious RCU usage at ./include/linux/inetdevice.h:LINE

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Date:   Thu, 2 Nov 2017 13:55:10 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Florian Westphal <fw@...len.de>
Cc:     syzbot 
        <bot+e52a2ae091b628f72765583c9faedc961c83b7e7@...kaller.appspotmail.com>,
        David Miller <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Subject: Re: suspicious RCU usage at ./include/linux/inetdevice.h:LINE

On Thu, Nov 2, 2017 at 12:06 PM, Florian Westphal <fw@...len.de> wrote:
> Cong Wang <xiyou.wangcong@...il.com> wrote:
>> > CPU: 0 PID: 23859 Comm: syz-executor2 Not tainted 4.14.0-rc5+ #140
>> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> > Google 01/01/2011
>> > Call Trace:
>> >  __dump_stack lib/dump_stack.c:16 [inline]
>> >  dump_stack+0x194/0x257 lib/dump_stack.c:52
>> >  lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4665
>> >  __in_dev_get_rtnl include/linux/inetdevice.h:230 [inline]
>> >  fib_dump_info+0x1136/0x13d0 net/ipv4/fib_semantics.c:1377
>> >  inet_rtm_getroute+0xf97/0x2d70 net/ipv4/route.c:2785
>>
>> This is introduced by:
>>
>> commit 394f51abb3d04f33fb798f04b16ae6b0491ea4ec
>> Author: Florian Westphal <fw@...len.de>
>> Date:   Tue Aug 15 16:34:44 2017 +0200
>>
>>     ipv4: route: set ipv4 RTM_GETROUTE to not use rtnl
>>
>>     Signed-off-by: Florian Westphal <fw@...len.de>
>>     Signed-off-by: David S. Miller <davem@...emloft.net>
>>
>> Looks like we need a wrapper for rcu_dereference_protected(dev->ip_ptr).
>
> Yes, thats the alternative to
> https://patchwork.ozlabs.org/patch/833401/
>
> which switches to _rcu version.

Yeah, that works too.