INFO: task hung in cleanup

INFO: task hung in cleanup_net
Status: auto-closed as invalid on 2019/10/18 21:44
Reported-by: syzbot+f3ac9e1a2fbff3875adb@syzkaller.appspotmail.com
First crash: 596d, last: 228d

similar bugs (7):
Kernel	Title	Repro	Count	Last	Reported	Patched	Status
upstream	INFO: task hung in cleanup_net (2)		2	224d	224d	0/16	closed as invalid on 2019/05/08 13:05
android-44	INFO: task hung in cleanup_net		10	178d	220d	0/2	auto-closed as invalid on 2019/10/25 08:38
upstream	INFO: task hung in cleanup_net		1	729d	717d	3/16	fixed on 2018/01/03 02:35
linux-4.14	INFO: task hung in cleanup_net	C	11	33d	237d	0/1	upstream: reported C repro on 2019/04/13 10:16
upstream	INFO: task hung in cleanup_net (3)		1	158d	158d	0/16	auto-closed as invalid on 2019/10/25 14:21
android-414	INFO: task hung in cleanup_net	C	45	96d	239d	0/1	public: reported C repro on 2019/04/11 00:00
android-49	INFO: task hung in cleanup_net (2)		1	12d	12d	0/3	public: reported on 2019/11/24 03:35

Sample crash report:

INFO: task kworker/u4:0:6 blocked for more than 120 seconds.
      Not tainted 4.9.94-g8683408 #3
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:0    D26648     6      2 0x00000000
Workqueue: netns cleanup_net
 ffff8801d9b40000 ffff8801cc1c9f80 ffff8801a5326a00 ffff8801cd818000
 ffff8801db321b98 ffff8801d9b4f9d8 ffffffff838c040d ffff8801d9b408c8
 ffffed003b368118 ffff8801d9b40000 00fffc0000000000 ffff8801db322468
Call Trace:
 [<ffffffff838c1a0f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3557
 [<ffffffff838c2393>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3590
 [<ffffffff838c6816>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff838c6816>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff82f3596f>] cleanup_net+0x13f/0x630 net/core/net_namespace.c:439
 [<ffffffff8118ae01>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118bbf6>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119ad2d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838d14dc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373

Showing all locks held in the system:
3 locks held by kworker/u4:0/6:
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118ad0e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118ad0e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118ad0e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118ad0e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  (net_cleanup_work){+.+.+.}, at: [<ffffffff8118ad48>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff82f3596f>] cleanup_net+0x13f/0x630 net/core/net_namespace.c:439
3 locks held by kworker/0:1/25:
 #0:  ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118ad0e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118ad0e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118ad0e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("%s"("ipv6_addrconf")){.+.+..}, at: [<ffffffff8118ad0e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((addr_chk_work).work){+.+...}, at: [<ffffffff8118ad48>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f8e6a7>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
2 locks held by khungtaskd/515:
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646bc>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff813646bc>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff81423bb0>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
3 locks held by kworker/1:3/1812:
 #0:  ("events_power_efficient"){.+.+.+}, at: [<ffffffff8118ad0e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("events_power_efficient"){.+.+.+}, at: [<ffffffff8118ad0e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("events_power_efficient"){.+.+.+}, at: [<ffffffff8118ad0e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("events_power_efficient"){.+.+.+}, at: [<ffffffff8118ad0e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  ((reg_check_chans).work){+.+...}, at: [<ffffffff8118ad48>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f8e6a7>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
1 lock held by rsyslogd/3650:
 #0:  (&f->f_pos_lock){+.+.+.}, at: [<ffffffff815d565c>] __fdget_pos+0xac/0xd0 fs/file.c:781
2 locks held by getty/3747:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff838cf4b2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff82007082>] n_tty_read+0x202/0x16b0 drivers/tty/n_tty.c:2133
2 locks held by syz-executor1/8437:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff82f35fb5>] copy_net_ns+0x155/0x290 net/core/net_namespace.c:406
 #1:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f8e6a7>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
1 lock held by syz-executor1/8620:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff82f35fb5>] copy_net_ns+0x155/0x290 net/core/net_namespace.c:406
2 locks held by syz-executor7/8461:
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f8e6a7>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 #1:  (ipvs->sync_mutex){+.+.+.}, at: [<ffffffff831bc58d>] do_ip_vs_set_ctl+0x90d/0xbd0 net/netfilter/ipvs/ip_vs_ctl.c:2397
1 lock held by syz-executor7/8472:
 #0:  (ipvs->sync_mutex){+.+.+.}, at: [<ffffffff831bc2c5>] do_ip_vs_set_ctl+0x645/0xbd0 net/netfilter/ipvs/ip_vs_ctl.c:2402
1 lock held by ipvs-b:3:0/8469:
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82f8e6a7>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 515 Comm: khungtaskd Not tainted 4.9.94-g8683408 #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d84b7d08 ffffffff81d9b509 0000000000000000 0000000000000001
 0000000000000001 0000000000000001 ffffffff810b7d60 ffff8801d84b7d40
 ffffffff81da6837 0000000000000001 0000000000000000 0000000000000002
Call Trace:
 [<ffffffff81d9b509>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81d9b509>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81da6837>] nmi_cpu_backtrace.cold.2+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81da67ca>] nmi_trigger_cpumask_backtrace+0x12a/0x14f lib/nmi_backtrace.c:60
 [<ffffffff810b7e64>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff81364c54>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff81364c54>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff81364c54>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff81364c54>] watchdog+0x6b4/0xa20 kernel/hung_task.c:239
 [<ffffffff8119ad2d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff838d14dc>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at pc 0xffffffff838cff16

Crashes (4):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Maintainers
ci-android-49-kasan-gce	2018/04/18 20:10	https://android.googlesource.com/kernel/common android-4.9	8683408f	829f0234	.config	log	report	davem@davemloft.net, ebiederm@xmission.com, edumazet@google.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, nicolas.dichtel@6wind.com, roman.kapl@sysgo.com
ci-android-49-kasan-gce-root	2019/04/21 21:43	https://android.googlesource.com/kernel/common android-4.9	1ef64dae	b0e8efcb	.config	log	report	davem@davemloft.net, edumazet@google.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org
ci-android-49-kasan-gce-root	2019/04/19 06:42	https://android.googlesource.com/kernel/common android-4.9	5d68df32	b0e8efcb	.config	log	report	davem@davemloft.net, edumazet@google.com, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org
ci-android-49-kasan-gce-root	2019/01/04 03:41	https://android.googlesource.com/kernel/common android-4.9	043c92bd	7da23925	.config	log	report	alexander.levin@microsoft.com, davem@davemloft.net, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, roman.kapl@sysgo.com