Re: INFO: task hung in fib6_rules_net_exit

From: Dmitry Vyukov
Date: Sat Mar 31 2018 - 12:17:08 EST


#syz dup: INFO: task hung in netdev_run_todo

On Sat, Mar 31, 2018 at 6:14 PM, syzbot
<syzbot+69bf48842d5035daa7a6@xxxxxxxxxxxxxxxxxxxxxxxxx> 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=69bf48842d5035daa7a6
>
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output:
> https://syzkaller.appspot.com/x/log.txt?id=5281628851011584
> 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+69bf48842d5035daa7a6@xxxxxxxxxxxxxxxxxxxxxxxxx
> 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.
>
> netlink: 8 bytes leftover after parsing attributes in process
> `syz-executor5'.
> IPVS: stopping backup sync thread 7398 ...
> INFO: task kworker/u4:3:163 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/u4:3 D19440 163 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
> fib6_rules_net_exit+0x12/0x50 net/ipv6/fib6_rules.c:392
> ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:151
> 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 1
> CPU: 1 PID: 868 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 1 to CPUs 0:
> NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10
> arch/x86/include/asm/irqflags.h:54
> Kernel panic - not syncing: hung_task: blocked tasks
> CPU: 1 PID: 868 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..
>
>
> ---
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