unregister_netdevice: waiting for lo to become free. Usage count = 3 INFO: task syz-executor2:31118 blocked for more than 120 seconds. Not tainted 4.15.0+ #296 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor2 D23552 31118 13675 0x00000004 Call Trace: context_switch kernel/sched/core.c:2845 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3421 schedule+0xf5/0x430 kernel/sched/core.c:3480 io_schedule+0x1c/0x70 kernel/sched/core.c:5096 wait_on_page_bit_common+0x4b3/0x770 mm/filemap.c:1099 wait_on_page_bit mm/filemap.c:1132 [inline] wait_on_page_writeback include/linux/pagemap.h:546 [inline] __filemap_fdatawait_range+0x282/0x430 mm/filemap.c:533 filemap_fdatawait_keep_errors+0x2a/0xb0 mm/filemap.c:600 fdatawait_one_bdev+0x50/0x70 fs/sync.c:95 iterate_bdevs+0x109/0x260 fs/block_dev.c:2147 sys_sync+0x120/0x1c0 fs/sync.c:117 entry_SYSCALL_64_fastpath+0x29/0xa0 RIP: 0033:0x453299 RSP: 002b:00007f1040c9fc58 EFLAGS: 00000212 ORIG_RAX: 00000000000000a2 RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000453299 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 000000000000006d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006efad8 R13: 00000000ffffffff R14: 00007f1040ca06d4 R15: 0000000000000000 Showing all locks held in the system: 2 locks held by khungtaskd/758: #0: (rcu_read_lock){....}, at: [<00000000cf09bc2f>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000cf09bc2f>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<0000000039301df7>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470 1 lock held by rsyslogd/4018: #0: (&f->f_pos_lock){+.+.}, at: [<0000000027573138>] __fdget_pos+0x12b/0x190 fs/file.c:765 2 locks held by getty/4139: #0: (&tty->ldisc_sem){++++}, at: [<000000001b218c39>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000251f3545>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4140: #0: (&tty->ldisc_sem){++++}, at: [<000000001b218c39>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000251f3545>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4141: #0: (&tty->ldisc_sem){++++}, at: [<000000001b218c39>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000251f3545>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4142: #0: (&tty->ldisc_sem){++++}, at: [<000000001b218c39>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000251f3545>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4143: #0: (&tty->ldisc_sem){++++}, at: [<000000001b218c39>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000251f3545>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4144: #0: (&tty->ldisc_sem){++++}, at: [<000000001b218c39>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000251f3545>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4145: #0: (&tty->ldisc_sem){++++}, at: [<000000001b218c39>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000251f3545>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 3 locks held by kworker/u4:6/7705: #0: ((wq_completion)"writeback"){+.+.}, at: [<00000000d2829d14>] process_one_work+0xaaf/0x1af0 kernel/workqueue.c:2084 #1: ((work_completion)(&(&wb->dwork)->work)){+.+.}, at: [<00000000597c6c27>] process_one_work+0xb01/0x1af0 kernel/workqueue.c:2088 #2: (&type->s_umount_key#27){.+.+}, at: [<00000000cd137a19>] trylock_super+0x20/0x100 fs/super.c:395 4 locks held by kworker/u4:11/11490: #0: ((wq_completion)"%s""netns"){+.+.}, at: [<00000000d2829d14>] process_one_work+0xaaf/0x1af0 kernel/workqueue.c:2084 #1: (net_cleanup_work){+.+.}, at: [<00000000597c6c27>] process_one_work+0xb01/0x1af0 kernel/workqueue.c:2088 #2: (net_mutex){+.+.}, at: [<0000000077ee2958>] cleanup_net+0x242/0xcc0 net/core/net_namespace.c:484 #3: (rcu_sched_state.barrier_mutex){+.+.}, at: [<0000000027d0a2ea>] _rcu_barrier+0x142/0x750 kernel/rcu/tree.c:3517 1 lock held by blkid/31022: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000d45addd4>] blkdev_put+0x2a/0x4f0 fs/block_dev.c:1793 1 lock held by syz-executor2/31118: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000ba49cf49>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:2145 1 lock held by syz-executor2/31133: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000ba49cf49>] iterate_bdevs+0xc8/0x260 fs/block_dev.c:2145 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 758 Comm: khungtaskd Not tainted 4.15.0+ #296 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+0x194/0x257 lib/dump_stack.c:53 nmi_cpu_backtrace+0x1d2/0x210 lib/nmi_backtrace.c:103 nmi_trigger_cpumask_backtrace+0x122/0x180 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:542 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