unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 unregister_netdevice: waiting for lo to become free. Usage count = 1 INFO: task syz-executor0:17801 blocked for more than 120 seconds. Not tainted 4.16.0+ #16 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor0 D25096 17801 4527 0x00000004 Call Trace: context_switch kernel/sched/core.c:2848 [inline] __schedule+0x807/0x1e40 kernel/sched/core.c:3490 schedule+0xef/0x430 kernel/sched/core.c:3549 __rwsem_down_write_failed_common+0x919/0x15d0 kernel/locking/rwsem-xadd.c:566 rwsem_down_write_failed+0xe/0x10 kernel/locking/rwsem-xadd.c:595 call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117 __down_write arch/x86/include/asm/rwsem.h:142 [inline] down_write+0xa2/0x120 kernel/locking/rwsem.c:72 register_netdevice_notifier+0xb4/0x8f0 net/core/dev.c:1629 bcm_init+0x259/0x300 net/can/bcm.c:1484 can_create+0x28a/0x4b0 net/can/af_can.c:183 __sock_create+0x526/0x920 net/socket.c:1285 sock_create net/socket.c:1325 [inline] __sys_socket+0x100/0x250 net/socket.c:1355 SYSC_socket net/socket.c:1364 [inline] SyS_socket+0x24/0x30 net/socket.c:1362 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x455259 RSP: 002b:00007f53165aec68 EFLAGS: 00000246 ORIG_RAX: 0000000000000029 RAX: ffffffffffffffda RBX: 00007f53165af6d4 RCX: 0000000000455259 RDX: 0000000000000002 RSI: 0000000000000002 RDI: 000000000000001d RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 0000000000000613 R14: 00000000006fc268 R15: 0000000000000000 Showing all locks held in the system: 3 locks held by kworker/u4:4/250: #0: 00000000fa71b1e4 ((wq_completion)"%s""netns"){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline] #0: 00000000fa71b1e4 ((wq_completion)"%s""netns"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 00000000fa71b1e4 ((wq_completion)"%s""netns"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 00000000fa71b1e4 ((wq_completion)"%s""netns"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline] #0: 00000000fa71b1e4 ((wq_completion)"%s""netns"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 00000000fa71b1e4 ((wq_completion)"%s""netns"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 00000000fa71b1e4 ((wq_completion)"%s""netns"){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116 #1: 0000000046c099b2 (net_cleanup_work){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120 #2: 00000000b2cb578c (pernet_ops_rwsem){++++}, at: cleanup_net+0x11a/0xb20 net/core/net_namespace.c:490 2 locks held by khungtaskd/889: #0: 00000000713ef4c9 (rcu_read_lock){....}, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: 00000000713ef4c9 (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249 #1: 000000008bfdb2b8 (tasklist_lock){.+.+}, at: debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470 2 locks held by getty/4451: #0: 00000000e5a1adc2 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000989a71b5 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4452: #0: 0000000011a8fc85 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000d95be997 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4453: #0: 00000000e384f3d2 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000d06eb0c2 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4454: #0: 000000006ede3cf5 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000a0e15bfe (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4455: #0: 00000000a8aa7472 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000d57b6008 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4456: #0: 000000009cedb03a (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000ccc1aec7 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4457: #0: 000000009588eb83 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000ec14c1c2 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 1 lock held by syz-executor0/17801: #0: 00000000b2cb578c (pernet_ops_rwsem){++++}, at: register_netdevice_notifier+0xb4/0x8f0 net/core/dev.c:1629 1 lock held by syz-executor0/17832: #0: 00000000b2cb578c (pernet_ops_rwsem){++++}, at: register_netdevice_notifier+0xb4/0x8f0 net/core/dev.c:1629 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 889 Comm: khungtaskd Not tainted 4.16.0+ #16 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1b9/0x294 lib/dump_stack.c:113 nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x151/0x192 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+0xc10/0xf60 kernel/hung_task.c:249 kthread+0x345/0x410 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411 Sending NMI from CPU 0 to CPUs 1: unregister_netdevice: waiting for lo to become free. Usage count = 1 NMI backtrace for cpu 1 CPU: 1 PID: 250 Comm: kworker/u4:4 Not tainted 4.16.0+ #16 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: netns cleanup_net RIP: 0010:_find_next_bit lib/find_bit.c:43 [inline] RIP: 0010:find_next_bit+0x34/0x130 lib/find_bit.c:74 RSP: 0018:ffff8801db1078f8 EFLAGS: 00000006 RAX: ffff8801d905a340 RBX: 0000000000000016 RCX: ffffffff83348f46 RDX: 0000000000000100 RSI: ffffffff83348f54 RDI: 0000000000000006 RBP: ffff8801db107920 R08: ffff8801d905a340 R09: ffffed003b6246d0 R10: ffffed003b6246d0 R11: ffff8801db123683 R12: 0000000000000000 R13: 0000000000000040 R14: ffff8801db1236d8 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8801db100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000001846000 CR3: 00000001b24e9000 CR4: 00000000001406e0 DR0: 0000000000000035 DR1: 0000000000000000 DR2: 000000000000fd85 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: next_pending_bucket kernel/time/timer.c:1406 [inline] __next_timer_interrupt+0x120/0x1a0 kernel/time/timer.c:1426 collect_expired_timers kernel/time/timer.c:1599 [inline] __run_timers+0x243/0xc50 kernel/time/timer.c:1662 run_timer_softirq+0x4c/0x70 kernel/time/timer.c:1692 __do_softirq+0x2e0/0xaf5 kernel/softirq.c:285 invoke_softirq kernel/softirq.c:365 [inline] irq_exit+0x1d1/0x200 kernel/softirq.c:405 exiting_irq arch/x86/include/asm/apic.h:525 [inline] smp_apic_timer_interrupt+0x17e/0x710 arch/x86/kernel/apic/apic.c:1052 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:862 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:783 [inline] RIP: 0010:console_trylock_spinning kernel/printk/printk.c:1677 [inline] RIP: 0010:vprintk_emit+0xbd0/0xdd0 kernel/printk/printk.c:1905 RSP: 0018:ffff8801d906ed38 EFLAGS: 00000293 ORIG_RAX: ffffffffffffff13 RAX: ffff8801d905a340 RBX: 0000000000000200 RCX: 1ffff1003b20b585 RDX: 0000000000000000 RSI: ffffffff815f5707 RDI: 0000000000000293 RBP: ffff8801d906eec8 R08: ffff8801d905abb8 R09: 0000000000000006 R10: ffff8801d905a340 R11: 0000000000000000 R12: 1ffffffff1162f7d R13: 0000000000000044 R14: ffffed003b20ddc4 R15: ffffffff8a489220 vprintk_default+0x28/0x30 kernel/printk/printk.c:1946 vprintk_func+0x7a/0xe7 kernel/printk/printk_safe.c:379 printk+0x9e/0xba kernel/printk/printk.c:1979 netdev_wait_allrefs.cold.141+0x17/0x3f net/core/dev.c:8146 netdev_run_todo+0x41a/0xa50 net/core/dev.c:8205 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:114 default_device_exit_batch+0x456/0x540 net/core/dev.c:9006 ops_exit_list.isra.7+0x105/0x160 net/core/net_namespace.c:155 cleanup_net+0x51d/0xb20 net/core/net_namespace.c:523 process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145 worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279 kthread+0x345/0x410 kernel/kthread.c:238 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411 Code: 89 fe 41 55 49 89 f5 41 54 53 48 89 d3 e8 15 7e 42 fe 48 89 de 4c 89 ef e8 ba 7e 42 fe 49 39 dd 0f 86 d0 00 00 00 e8 fc 7d 42 fe <48> 89 d8 48 c1 e8 06 4d 8d 3c c6 48 b8 00 00 00 00 00 fc ff df INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.047 msecs