Date:   Sat, 31 Mar 2018 17:44:49 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+5093dde0c59c3c1f74e8@...kaller.appspotmail.com>
Cc:     Christian Brauner <christian.brauner@...ntu.com>,
        David Miller <davem@...emloft.net>,
        David Ahern <dsahern@...il.com>,
        Florian Westphal <fw@...len.de>, Jiri Benc <jbenc@...hat.com>,
        Kirill Tkhai <ktkhai@...tuozzo.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Xin Long <lucien.xin@...il.com>,
        netdev <netdev@...r.kernel.org>, syzkaller-bugs@...glegroups.com,
        Vladislav Yasevich <vyasevich@...il.com>
Subject: Re: INFO: task hung in tunnel_key_exit_net

#syz dup: INFO: task hung in netdev_run_todo

On Sat, Mar 31, 2018 at 5:43 PM, syzbot
<syzbot+5093dde0c59c3c1f74e8@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on net-next commit
> 18845557fd6fc1998f2d0d8c30467f86db587529 (Thu Mar 29 20:24:06 2018 +0000)
> Merge tag 'wireless-drivers-next-for-davem-2018-03-29' of
> git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers-next
> syzbot dashboard link:
> https://syzkaller.appspot.com/bug?extid=5093dde0c59c3c1f74e8
>
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=5957616438083584
> Kernel config: https://syzkaller.appspot.com/x/.config?id=-37309782588693906
> compiler: gcc (GCC) 7.1.1 20170620
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+5093dde0c59c3c1f74e8@...kaller.appspotmail.com
> It will help syzbot understand when the bug is fixed. See footer for
> details.
> If you forward the report, please keep this part and the footer.
>
> IPVS: sync thread started: state = BACKUP, mcast_ifn = lo, syncid = 4, id =
> 0
> IPVS: stopping backup sync thread 24307 ...
> INFO: task kworker/u4:10:9047 blocked for more than 120 seconds.
>       Not tainted 4.16.0-rc6+ #286
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> kworker/u4:10   D21104  9047      2 0x80000000
> Workqueue: netns cleanup_net
> Call Trace:
>  context_switch kernel/sched/core.c:2862 [inline]
>  __schedule+0x8fb/0x1ec0 kernel/sched/core.c:3440
>  schedule+0xf5/0x430 kernel/sched/core.c:3499
>  schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3557
>  __mutex_lock_common kernel/locking/mutex.c:833 [inline]
>  __mutex_lock+0xaad/0x1a80 kernel/locking/mutex.c:893
>  mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
>  rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
>  tc_action_net_exit include/net/act_api.h:132 [inline]
>  tunnel_key_exit_net+0x7a/0x3b0 net/sched/act_tunnel_key.c:334
>  ops_exit_list.isra.6+0x100/0x150 net/core/net_namespace.c:154
>  cleanup_net+0x4d8/0xa90 net/core/net_namespace.c:522
>  process_one_work+0xc47/0x1bb0 kernel/workqueue.c:2113
>  worker_thread+0x223/0x1990 kernel/workqueue.c:2247
>  kthread+0x33c/0x400 kernel/kthread.c:238
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406
> INFO: lockdep is turned off.
> NMI backtrace for cpu 0
> CPU: 0 PID: 869 Comm: khungtaskd Not tainted 4.16.0-rc6+ #286
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x24d lib/dump_stack.c:53
>  nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103
>  nmi_trigger_cpumask_backtrace+0x123/0x180 lib/nmi_backtrace.c:62
>  arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
>  trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline]
>  check_hung_task kernel/hung_task.c:132 [inline]
>  check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
>  watchdog+0x90c/0xd60 kernel/hung_task.c:249
>  kthread+0x33c/0x400 kernel/kthread.c:238
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406
> Sending NMI from CPU 0 to CPUs 1:
> NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10
> arch/x86/include/asm/irqflags.h:54
> Kernel panic - not syncing: hung_task: blocked tasks
> CPU: 0 PID: 869 Comm: khungtaskd Not tainted 4.16.0-rc6+ #286
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:17 [inline]
>  dump_stack+0x194/0x24d lib/dump_stack.c:53
>  panic+0x1e4/0x41c kernel/panic.c:183
>  check_hung_task kernel/hung_task.c:133 [inline]
>  check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
>  watchdog+0x91d/0xd60 kernel/hung_task.c:249
>  kthread+0x33c/0x400 kernel/kthread.c:238
>  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
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