From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: David Ahern <dsahern@gmail.com>,
syzbot
<bot+21b498fc12cf2041655f8e1eeae0733807d794b3@syzkaller.appspotmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
syzkaller-bugs@googlegroups.com,
David Miller <davem@davemloft.net>,
Florian Westphal <fw@strlen.de>,
Daniel Borkmann <daniel@iogearbox.net>,
Xin Long <lucien.xin@gmail.com>,
jakub.kicinski@netronome.com, mschiffer@universe-factory.net,
Vladislav Yasevich <vyasevich@gmail.com>,
Jiri Benc <jbenc@redhat.com>, netdev <netdev@vger.kernel.org>,
Neil Horman <nhorman@tuxdriver.com>,
linux-sctp@vger.kernel.org
Subject: Re: INFO: task hung in bpf_exit_net
Date: Fri, 22 Dec 2017 17:04:37 -0200 [thread overview]
Message-ID: <20171222190437.GC6123@localhost.localdomain> (raw)
In-Reply-To: <20171222182807.GC32765@localhost.localdomain>
On Fri, Dec 22, 2017 at 04:28:07PM -0200, Marcelo Ricardo Leitner wrote:
> On Fri, Dec 22, 2017 at 11:58:08AM +0100, Dmitry Vyukov wrote:
> ...
> > > Same with this one, perhaps related to / fixed by:
> > > http://patchwork.ozlabs.org/patch/850957/
> > >
> >
> >
> >
> > Looking at the log, this one seems to be an infinite loop in SCTP code
> > with console output in it. Kernel is busy printing gazilion of:
> >
> > [ 176.491099] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > low, using default minimum of 512
> > ** 110 printk messages dropped **
> > [ 176.503409] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > low, using default minimum of 512
> > ** 103 printk messages dropped **
> > ...
> > [ 246.742374] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > low, using default minimum of 512
> > [ 246.742484] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > low, using default minimum of 512
> > [ 246.742590] sctp: sctp_transport_update_pmtu: Reported pmtu 508 too
> > low, using default minimum of 512
> >
> > Looks like a different issue.
> >
>
> Oh. I guess this is caused by the interface having a MTU smaller than
> SCTP_DEFAULT_MINSEGMENT (512), as the icmp frag needed handler
> (sctp_icmp_frag_needed) will trigger an instant retransmission.
> But as the MTU is smaller, SCTP won't update it, but will issue the
> retransmission anyway.
>
> I will test this soon. Should be fairly easy to trigger it.
Reproduced it.
netns A veth0(1500) - veth1(1500) B veth2(508) - veth3(508) C
When A sends a sctp packet bigger than 508, it triggers the issue as B
will reply a icmp frag needed with a size that sctp won't accept but
will retransmit anyway.
Marcelo
next prev parent reply other threads:[~2017-12-22 19:04 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <001a1143fd00a8cc790560b0b552@google.com>
2017-12-19 12:47 ` INFO: task hung in bpf_exit_net Dmitry Vyukov
2017-12-19 16:21 ` Xin Long
2017-12-19 18:20 ` David Ahern
2017-12-22 10:58 ` Dmitry Vyukov
2017-12-22 11:16 ` Marcelo Ricardo Leitner
2017-12-22 11:24 ` Dmitry Vyukov
2017-12-22 18:28 ` Marcelo Ricardo Leitner
2017-12-22 19:04 ` Marcelo Ricardo Leitner [this message]
2018-02-02 23:39 ` Eric Biggers
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