netdev - Re: INFO: rcu detected stall in corrupted

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Date:   Wed, 23 May 2018 20:13:40 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        syzbot+f116bc1994efe725d51b@...kaller.appspotmail.com,
        kuznet@....inr.ac.ru, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        yoshfuji@...ux-ipv6.org, dsahern@...nel.org,
        roopa@...ulusnetworks.com, linux-sctp@...r.kernel.org,
        Xin Long <lucien.xin@...il.com>
Subject: Re: INFO: rcu detected stall in corrupted

On Mon, May 21, 2018 at 11:13:46AM -0700, Eric Dumazet wrote:
> 
> 
> On 05/21/2018 11:09 AM, David Miller wrote:
> > From: syzbot <syzbot+f116bc1994efe725d51b@...kaller.appspotmail.com>
> > Date: Mon, 21 May 2018 11:05:02 -0700
> > 
> >>  find_match+0x244/0x13a0 net/ipv6/route.c:691
> >>  find_rr_leaf net/ipv6/route.c:729 [inline]
> >>  rt6_select net/ipv6/route.c:779 [inline]
> > 
> > Hmmm, endless loop in find_rr_leaf or similar?
> > 
> 
> 
> I do not think so, this really looks like SCTP specific 
> , we now have dozens of traces all sharing :
> 
>  sctp_transport_route+0xad/0x450 net/sctp/transport.c:293
>  sctp_packet_config+0xb89/0xfd0 net/sctp/output.c:123
>  sctp_outq_flush+0x79c/0x4370 net/sctp/outqueue.c:894
>  sctp_outq_uncork+0x6a/0x80 net/sctp/outqueue.c:776
>  sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1820 [inline]
>  sctp_side_effects net/sctp/sm_sideeffect.c:1220 [inline]
>  sctp_do_sm+0x596/0x7160 net/sctp/sm_sideeffect.c:1191
>  sctp_generate_heartbeat_event+0x218/0x450 net/sctp/sm_sideeffect.c:406
>  call_timer_fn+0x230/0x940 kernel/time/timer.c:1326 
> 
> 
> Some kind of infinite loop.
> 
> When the hrtimer fires, it can point to any code that sits below but does not necessarily have a bug.

Agreed. Xin Long identified the root cause. syzkaller is setting too
aggressive parameters to SCTP RTO, leading to issues with the
heartbeat timer.