From: Cong Wang <xiyou.wangcong@gmail.com>
To: Julian Anastasov <ja@ssi.bg>
Cc: syzbot+30209ea299c09d8785c9@syzkaller.appspotmail.com,
ddstreet@ieee.org, Dmitry Vyukov <dvyukov@google.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
syzkaller-bugs@googlegroups.com
Subject: Re: unregister_netdevice: waiting for DEV to become free (2)
Date: Mon, 20 Aug 2018 22:40:43 -0700 [thread overview]
Message-ID: <CAM_iQpVM4wHkW4RKMuDj_Jjof3XbJmAsN0SdSRfneaf94CL0cw@mail.gmail.com> (raw)
In-Reply-To: <alpine.LFD.2.20.1808201527230.2758@ja.home.ssi.bg>
On Mon, Aug 20, 2018 at 6:00 AM Julian Anastasov <ja@ssi.bg> wrote:
>
>
> Hello,
>
> On Sun, 19 Aug 2018, syzbot wrote:
>
> > syzbot has found a reproducer for the following crash on:
> >
> > HEAD commit: d7857ae43dcc Add linux-next specific files for 20180817
> > git tree: linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=13c72fce400000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=4b10cd1ea76bb092
> > dashboard link: https://syzkaller.appspot.com/bug?extid=30209ea299c09d8785c9
> > compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> > syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=15df679a400000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15242741400000
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+30209ea299c09d8785c9@syzkaller.appspotmail.com
> >
> > IPVS: stopping master sync thread 4657 ...
> > IPVS: stopping master sync thread 4663 ...
> > IPVS: sync thread started: state = MASTER, mcast_ifn = syz_tun, syncid = 0, id
> > IPVS: = 0
> > IPVS: sync thread started: state = MASTER, mcast_ifn = syz_tun, syncid = 0, id
> > IPVS: = 0
> > IPVS: stopping master sync thread 4664 ...
> > unregister_netdevice: waiting for lo to become free. Usage count = 1
>
> Well, only IPVS and tun in the game? But IPVS does not
> take any dev references for sync threads. Can it be a problem
> in tun? For example, a side effects from dst_cache_reset?
> May be dst_release is called too late? Here is what should happen
> on unregistration:
There are multiple similar bugs grouped together under this, perhaps
they are different, perhaps they are a same bug, too early to say.
For the one I look into, dst_cache doesn't matter, because the xmit
path doesn't even use tunnel dst_cache at all, and it is ip6tnl0 FB
device, unlike this one which is tun device.
>
> - NETDEV_UNREGISTER event: rt_flush_dev changes dst->dev with lo
> but dst is not released
>
> - ndo_uninit/ip_tunnel_uninit: dst_cache_reset is called which
> does nothing!?! May be dst_release call is needed here.
I think this makes sense, at least prior to the general dst_cache
introduction, dst refcnt was released in ndo_uninit() too, so it
is reasonable to move the dst_cache_destroy() to ndo_uninit().
>
> - no more references are expected here ...
>
> - netdev_run_todo -> netdev_wait_allrefs: loop here due to refcnt!=0
>
> - dev->priv_destructor (ip_tunnel_dev_free) calls dst_cache_destroy
> where dst_release is used but it is not reached because we loop in
> netdev_wait_allrefs above
>
> - dst_cache_destroy: really call dst_release
>
> In fact, after calling rt_flush_dev and replacing the
> dst->dev we should reach dev->priv_destructor (ip_tunnel_dev_free)
> for tun device where dst_release for lo should be called. But may be
> something prevents it, exit batching?
I can't see anything in netnns exit batch is any special here.
For the one I look into, it seems some fib6_info is not released for
some reason. It seems to be the one created by addrconf_prefix_route(),
which is supposed to be released by fib6_clean_tree() I think, but it
never happens.
Thanks.
next prev parent reply other threads:[~2018-08-21 5:40 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <00000000000056268e05737dcb95@google.com>
[not found] ` <000000000000c5b63005737f290d@google.com>
2018-08-15 20:41 ` unregister_netdevice: waiting for DEV to become free (2) Dmitry Vyukov
2018-08-20 4:31 ` syzbot
2018-08-20 12:55 ` Julian Anastasov
2018-08-21 5:40 ` Cong Wang [this message]
2018-08-22 4:11 ` Julian Anastasov
2019-04-15 13:36 ` Tetsuo Handa
2019-04-15 15:35 ` David Ahern
2019-04-21 20:41 ` Stephen Suryaputra
2019-04-22 14:58 ` David Ahern
2019-04-22 16:04 ` Eric Dumazet
2019-04-22 16:09 ` Eric Dumazet
2019-04-16 14:00 ` Tetsuo Handa
2019-04-26 13:43 ` Tetsuo Handa
2019-04-27 17:16 ` David Ahern
2019-04-27 22:33 ` Tetsuo Handa
2019-04-27 23:52 ` Eric Dumazet
2019-04-28 4:22 ` Tetsuo Handa
2019-04-28 15:04 ` Eric Dumazet
2019-04-29 18:34 ` David Ahern
2019-04-29 18:43 ` David Ahern
2019-05-01 13:38 ` Tetsuo Handa
2019-05-01 14:52 ` David Ahern
2019-05-01 16:16 ` Tetsuo Handa
2019-05-04 14:52 ` [PATCH] ipv4: Delete uncached routes upon unregistration of loopback device Tetsuo Handa
2019-05-04 15:56 ` Eric Dumazet
2019-05-04 17:09 ` Tetsuo Handa
2019-05-04 17:24 ` Eric Dumazet
2019-05-04 20:13 ` Julian Anastasov
2019-11-28 9:56 ` unregister_netdevice: waiting for DEV to become free (2) Tetsuo Handa
2019-11-29 5:54 ` Lukas Bulwahn
2019-11-29 6:51 ` Jouni Högander
2019-12-05 10:00 ` Jouni Högander
2019-12-05 11:00 ` Tetsuo Handa
2019-12-16 11:12 ` Tetsuo Handa
2019-12-17 7:08 ` Jouni Högander
2019-10-11 10:14 ` Tetsuo Handa
2019-10-11 15:12 ` Alexei Starovoitov
2019-10-16 10:34 ` Toke Høiland-Jørgensen
2019-11-15 9:43 ` Tetsuo Handa
2019-11-21 11:36 ` Toke Høiland-Jørgensen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAM_iQpVM4wHkW4RKMuDj_Jjof3XbJmAsN0SdSRfneaf94CL0cw@mail.gmail.com \
--to=xiyou.wangcong@gmail.com \
--cc=ddstreet@ieee.org \
--cc=dvyukov@google.com \
--cc=ja@ssi.bg \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=syzbot+30209ea299c09d8785c9@syzkaller.appspotmail.com \
--cc=syzkaller-bugs@googlegroups.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).