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-executor6:23509 blocked for more than 120 seconds. Not tainted 4.16.0+ #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor6 D22808 23509 22854 0x80000002 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 unregister_netdevice_notifier+0x98/0x520 net/core/dev.c:1698 bcm_release+0x93/0x5c0 net/can/bcm.c:1507 sock_release+0x96/0x1b0 net/socket.c:594 sock_close+0x16/0x20 net/socket.c:1149 __fput+0x34d/0x890 fs/file_table.c:209 ____fput+0x15/0x20 fs/file_table.c:243 task_work_run+0x1e4/0x290 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x1aee/0x2730 kernel/exit.c:865 do_group_exit+0x16f/0x430 kernel/exit.c:968 SYSC_exit_group kernel/exit.c:979 [inline] SyS_exit_group+0x1d/0x20 kernel/exit.c:977 do_syscall_64+0x29e/0x9d0 arch/x86/entry/common.c:287 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x455259 RSP: 002b:00007fff938fb428 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 000000000000000f RCX: 0000000000455259 RDX: 0000000000000000 RSI: 00000000007319c8 RDI: 0000000000000000 RBP: 0000000000000013 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000013 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000001380 Showing all locks held in the system: 2 locks held by khungtaskd/882: #0: 000000007866c173 (rcu_read_lock){....}, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: 000000007866c173 (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249 #1: 00000000558219f4 (tasklist_lock){.+.+}, at: debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470 1 lock held by rsyslogd/4359: #0: 00000000eefa2b68 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0x1a9/0x1e0 fs/file.c:766 2 locks held by getty/4450: #0: 0000000053be69e5 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000027c6adc (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4451: #0: 000000000d2b616a (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 0000000041bb8199 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4452: #0: 00000000cd01dc5c (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000c7e674ce (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4453: #0: 00000000764816ee (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 000000000a6335da (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4454: #0: 000000003f26d900 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000ae6323d7 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 2 locks held by getty/4455: #0: 0000000034656c37 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000b6646cdd (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 3 locks held by kworker/u4:5/6754: #0: 00000000ed2f9874 ((wq_completion)"%s""netns"){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline] #0: 00000000ed2f9874 ((wq_completion)"%s""netns"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] #0: 00000000ed2f9874 ((wq_completion)"%s""netns"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline] #0: 00000000ed2f9874 ((wq_completion)"%s""netns"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline] #0: 00000000ed2f9874 ((wq_completion)"%s""netns"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline] #0: 00000000ed2f9874 ((wq_completion)"%s""netns"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline] #0: 00000000ed2f9874 ((wq_completion)"%s""netns"){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116 #1: 000000005b40ec25 (net_cleanup_work){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120 #2: 000000005fa1942b (pernet_ops_rwsem){++++}, at: cleanup_net+0x11a/0xb20 net/core/net_namespace.c:490 2 locks held by getty/19297: #0: 00000000adb1fd0c (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: 00000000c8cacf4d (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131 1 lock held by syz-executor6/23509: #0: 000000005fa1942b (pernet_ops_rwsem){++++}, at: unregister_netdevice_notifier+0x98/0x520 net/core/dev.c:1698 1 lock held by syz-executor6/23535: #0: 000000005fa1942b (pernet_ops_rwsem){++++}, at: copy_net_ns+0x297/0x4c0 net/core/net_namespace.c:432 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 882 Comm: khungtaskd Not tainted 4.16.0+ #4 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: NMI backtrace for cpu 1 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.16.0+ #4 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:lock_acquire+0x1c4/0x520 kernel/locking/lockdep.c:3920 RSP: 0018:ffff8801db1079c8 EFLAGS: 00000002 RAX: 0000000000000000 RBX: 1ffff1003b620f42 RCX: 0000000000000002 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff88a0da08 RBP: ffff8801db107ad8 R08: 0000000000000001 R09: 0000000000000001 R10: ffffed0043fff009 R11: ffff88021fff8057 R12: 0000000000000000 R13: 0000000000000002 R14: 0000000000000001 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8801db100000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000001557000 CR3: 00000001b2db2000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: seqcount_lockdep_reader_access include/linux/seqlock.h:81 [inline] read_seqcount_begin include/linux/seqlock.h:164 [inline] read_seqbegin include/linux/seqlock.h:433 [inline] tick_nohz_stop_sched_tick kernel/time/tick-sched.c:666 [inline] __tick_nohz_idle_enter+0x320/0x1710 kernel/time/tick-sched.c:918 tick_nohz_irq_exit+0x66/0x80 kernel/time/tick-sched.c:971 tick_irq_exit kernel/softirq.c:387 [inline] irq_exit+0x1bb/0x200 kernel/softirq.c:407 scheduler_ipi+0x52b/0xa30 kernel/sched/core.c:1778 smp_reschedule_interrupt+0xed/0x660 arch/x86/kernel/smp.c:277 reschedule_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:886 RIP: 0010:native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54 RSP: 0018:ffff8801d9ed7cb0 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff02 RAX: dffffc0000000000 RBX: 1ffff1003b3daf99 RCX: 0000000000000000 RDX: 1ffffffff1162e58 RSI: 0000000000000001 RDI: ffffffff88b172c0 RBP: ffff8801d9ed7cb0 R08: ffff8801d9ec8340 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001 R13: ffff8801d9ed7d68 R14: ffffffff88b172b0 R15: 0000000000000000 arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline] default_idle+0xc2/0x440 arch/x86/kernel/process.c:354 arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:345 default_idle_call+0x6d/0x90 kernel/sched/idle.c:93 cpuidle_idle_call kernel/sched/idle.c:151 [inline] do_idle+0x2f4/0x3c0 kernel/sched/idle.c:241 cpu_startup_entry+0x104/0x120 kernel/sched/idle.c:346 start_secondary+0x426/0x5b0 arch/x86/kernel/smpboot.c:267 secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:242 Code: 02 00 00 4c 8b 8d 20 ff ff ff 6a 00 44 89 e2 45 89 f0 6a 00 44 89 e9 ff 75 10 49 c1 e9 09 41 57 49 83 f1 01 48 8b bd 30 ff ff ff <8b> b5 2c ff ff ff 41 83 e1 01 65 4c 8b 24 25 c0 ed 01 00 e8 24