From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: INFO: rcu detected stall in kfree_skbmem
Date: Fri, 11 May 2018 12:08:33 -0700
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Cc: syzbot <syzbot+fc78715ba3b3257caf6a@syzkaller.appspotmail.com>,
        Vladislav Yasevich <vyasevich@gmail.com>,
        Neil Horman <nhorman@tuxdriver.com>,
        linux-sctp@vger.kernel.org, Andrei Vagin <avagin@virtuozzo.com>,
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To: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>
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On 05/11/2018 11:41 AM, Marcelo Ricardo Leitner wrote:

> But calling ip6_xmit with rcu_read_lock is expected. tcp stack also
> does it.
> Thus I think this is more of an issue with IPv6 stack. If a host has
> an extensive ip6tables ruleset, it probably generates this more
> easily.
> 
>>>  sctp_v6_xmit+0x4a5/0x6b0 net/sctp/ipv6.c:225
>>>  sctp_packet_transmit+0x26f6/0x3ba0 net/sctp/output.c:650
>>>  sctp_outq_flush+0x1373/0x4370 net/sctp/outqueue.c:1197
>>>  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
>>>  expire_timers kernel/time/timer.c:1363 [inline]
> 
> Having this call from a timer means it wasn't processing sctp stack
> for too long.
>

I feel the problem is that this part is looping, in some infinite loop.

I have seen this stack traces in other reports.

Maybe some kind of list corruption.