unregister_netdevice: waiting for lo to become free. Usage count = 5 INFO: task syz-executor1:24413 blocked for more than 120 seconds. Not tainted 4.15.0+ #285 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor1 D19344 24413 13867 0x80000006 Call Trace: context_switch kernel/sched/core.c:2799 [inline] __schedule+0x8eb/0x2060 kernel/sched/core.c:3375 schedule+0xf5/0x430 kernel/sched/core.c:3434 io_schedule+0x1c/0x70 kernel/sched/core.c:5042 wait_on_page_bit_common+0x4b3/0x770 mm/filemap.c:1100 wait_on_page_bit mm/filemap.c:1133 [inline] wait_on_page_writeback include/linux/pagemap.h:546 [inline] __filemap_fdatawait_range+0x27a/0x420 mm/filemap.c:534 filemap_fdatawait_range mm/filemap.c:559 [inline] filemap_fdatawait include/linux/fs.h:2596 [inline] filemap_write_and_wait+0x7a/0xd0 mm/filemap.c:625 __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:210 ____fput+0x15/0x20 fs/file_table.c:244 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+0x73f/0x16c0 kernel/signal.c:2335 do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809 exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158 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:00007f6bfc845c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000028 RAX: 0000000000011000 RBX: 000000000071bea0 RCX: 0000000000453299 RDX: 00000000200ddff8 RSI: 0000000000000015 RDI: 0000000000000014 RBP: 000000000000049b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000102000001 R11: 0000000000000212 R12: 00000000006f5f28 R13: 00000000ffffffff R14: 00007f6bfc8466d4 R15: 0000000000000000 Showing all locks held in the system: 3 locks held by kworker/u4:1/21: #0: ((wq_completion)"writeback"){+.+.}, at: [<00000000c2296a7c>] process_one_work+0xaaf/0x1b10 kernel/workqueue.c:2084 #1: ((work_completion)(&(&wb->dwork)->work)){+.+.}, at: [<00000000db74b262>] process_one_work+0xb01/0x1b10 kernel/workqueue.c:2088 #2: (&type->s_umount_key#27){.+.+}, at: [<00000000fdd45bb0>] trylock_super+0x20/0x100 fs/super.c:395 2 locks held by khungtaskd/759: #0: (rcu_read_lock){....}, at: [<00000000dc0481e4>] check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline] #0: (rcu_read_lock){....}, at: [<00000000dc0481e4>] watchdog+0x1c5/0xd60 kernel/hung_task.c:249 #1: (tasklist_lock){.+.+}, at: [<000000002b142a64>] debug_show_all_locks+0xd3/0x3d0 kernel/locking/lockdep.c:4465 4 locks held by kworker/u4:4/1629: #0: ((wq_completion)"%s""netns"){+.+.}, at: [<00000000c2296a7c>] process_one_work+0xaaf/0x1b10 kernel/workqueue.c:2084 #1: (net_cleanup_work){+.+.}, at: [<00000000db74b262>] process_one_work+0xb01/0x1b10 kernel/workqueue.c:2088 #2: (net_mutex){+.+.}, at: [<000000008e1f53a1>] cleanup_net+0x247/0xb50 net/core/net_namespace.c:450 #3: (rcu_sched_state.barrier_mutex){+.+.}, at: [<000000009219e73f>] _rcu_barrier+0x142/0x750 kernel/rcu/tree.c:3596 2 locks held by getty/4135: #0: (&tty->ldisc_sem){++++}, at: [<000000004f3674f1>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000288d7132>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4136: #0: (&tty->ldisc_sem){++++}, at: [<000000004f3674f1>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000288d7132>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4137: #0: (&tty->ldisc_sem){++++}, at: [<000000004f3674f1>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000288d7132>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4138: #0: (&tty->ldisc_sem){++++}, at: [<000000004f3674f1>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000288d7132>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4139: #0: (&tty->ldisc_sem){++++}, at: [<000000004f3674f1>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000288d7132>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4140: #0: (&tty->ldisc_sem){++++}, at: [<000000004f3674f1>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000288d7132>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 2 locks held by getty/4141: #0: (&tty->ldisc_sem){++++}, at: [<000000004f3674f1>] ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365 #1: (&ldata->atomic_read_lock){+.+.}, at: [<00000000288d7132>] n_tty_read+0x2ef/0x1a00 drivers/tty/n_tty.c:2131 1 lock held by syz-executor1/24413: #0: (&bdev->bd_mutex){+.+.}, at: [<00000000ed53f9c3>] __blkdev_put+0xbc/0x7f0 fs/block_dev.c:1757 1 lock held by blkid/24469: #0: (&bdev->bd_mutex){+.+.}, at: [<000000006dfaf329>] __blkdev_get+0x158/0x10e0 fs/block_dev.c:1439 1 lock held by syz-executor1/24473: #0: (net_mutex){+.+.}, at: [<0000000062beb432>] copy_net_ns+0x239/0x580 net/core/net_namespace.c:410 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 759 Comm: khungtaskd Not tainted 4.15.0+ #285 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:541 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