unregister_netdevice: waiting for lo to become free. Usage count = 3 INFO: task syz-executor0:28819 blocked for more than 120 seconds. Not tainted 4.15.0+ #295 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor0 D20096 28819 4214 0x80000006 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_range mm/filemap.c:558 [inline] filemap_fdatawait include/linux/fs.h:2590 [inline] filemap_write_and_wait+0x7a/0xd0 mm/filemap.c:624 __sync_blockdev fs/block_dev.c:448 [inline] sync_blockdev.part.28+0x50/0x70 fs/block_dev.c:457 sync_blockdev fs/block_dev.c:444 [inline] __blkdev_put+0x18b/0x7f0 fs/block_dev.c:1763 blkdev_put+0x85/0x4f0 fs/block_dev.c:1835 blkdev_close+0x8b/0xb0 fs/block_dev.c:1842 __fput+0x327/0x7e0 fs/file_table.c:209 ____fput+0x15/0x20 fs/file_table.c:243 task_work_run+0x199/0x270 kernel/task_work.c:113 exit_task_work include/linux/task_work.h:22 [inline] do_exit+0x9bb/0x1ad0 kernel/exit.c:865 do_group_exit+0x149/0x400 kernel/exit.c:968 get_signal+0x73a/0x16d0 kernel/signal.c:2469 do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809 exit_to_usermode_loop+0x258/0x2f0 arch/x86/entry/common.c:161 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264 entry_SYSCALL_64_fastpath+0x9e/0xa0 RIP: 0033:0x453299 RSP: 002b:00007f483ac14c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000028 RAX: 0000000000011000 RBX: 000000000071bea0 RCX: 0000000000453299 RDX: 00000000200ddff8 RSI: 0000000000000014 RDI: 0000000000000013 RBP: 00000000000004a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000100000001 R11: 0000000000000212 R12: 00000000006f5fa0 R13: 00000000ffffffff R14: 00007f483ac156d4 R15: 0000000000000000 Showing all locks held in the system: 3 locks held by kworker/u4:0/5: #0: ((wq_completion)"%s""netns"){+.+.}, at: [<000000000ecfc269>] process_one_work+0xaaf/0x1af0 kernel/workqueue.c:2084 #1: (net_cleanup_work){+.+.}, at: [<00000000005d1117>] process_one_work+0xb01/0x1af0 kernel/workqueue.c:2088 #2: (net_mutex){+.+.}, at: [<000000007e1f1b1f>] cleanup_net+0x242/0xcc0 net/core/net_namespace.c:484 3 locks held by kworker/u4:5/594: #0: ((wq_completion)"writeback"){+.+.}, at: [<000000000ecfc269>] process_one_work+0xaaf/0x1af0 kernel/workqueue.c:2084 #1: ((work_completion)(&(&wb->dwork)->work)){+.+.}, at: [<00000000005d1117>] process_one_work+0xb01/0x1af0 kernel/workqueue.c:2088 #2: (&type->s_umount_key#27){.+.+}, at: [<000000009cbaa930>] trylock_super+0x20/0x100 fs/super.c:395 2 locks held by khungtaskd/758: #0: (rcu_read_lock){....}, at: [<00000000a20347e9>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000a20347e9>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<00000000127b6f52>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4470 2 locks held by getty/4141: #0: (&tty->ldisc_sem){++++}, at: [<00000000dfb80beb>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008a78da2f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4142: #0: (&tty->ldisc_sem){++++}, at: [<00000000dfb80beb>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008a78da2f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4143: #0: (&tty->ldisc_sem){++++}, at: [<00000000dfb80beb>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008a78da2f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4144: #0: (&tty->ldisc_sem){++++}, at: [<00000000dfb80beb>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008a78da2f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4145: #0: (&tty->ldisc_sem){++++}, at: [<00000000dfb80beb>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008a78da2f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4146: #0: (&tty->ldisc_sem){++++}, at: [<00000000dfb80beb>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008a78da2f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4147: #0: (&tty->ldisc_sem){++++}, at: [<00000000dfb80beb>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<000000008a78da2f>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 1 lock held by syz-executor0/28819: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000bd206432>] __blkdev_put+0xbc/0x7f0 fs/block_dev.c:1757 1 lock held by blkid/28872: #0: (&bdev->bd_mutex){+.+.}, at: [<000000002536d58e>] __blkdev_get+0x158/0x10e0 fs/block_dev.c:1439 1 lock held by syz-executor0/28904: #0: (net_mutex){+.+.}, at: [<00000000fb9f3465>] copy_net_ns+0x1f5/0x580 net/core/net_namespace.c:417 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 758 Comm: khungtaskd Not tainted 4.15.0+ #295 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 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:54