INFO: task kworker/u4:0:5 blocked for more than 140 seconds. Not tainted 4.14.68+ #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u4:0 D26128 5 2 0x80000000 Workqueue: netns cleanup_net Call Trace: schedule+0x7f/0x1b0 kernel/sched/core.c:3490 schedule_timeout+0x710/0xe60 kernel/time/timer.c:1718 do_wait_for_common kernel/sched/completion.c:91 [inline] __wait_for_common kernel/sched/completion.c:112 [inline] wait_for_common+0x3bc/0x4e0 kernel/sched/completion.c:123 _rcu_barrier+0x27b/0x3f0 kernel/rcu/tree.c:3594 cleanup_net+0x4be/0x880 net/core/net_namespace.c:494 process_one_work+0x86e/0x15c0 kernel/workqueue.c:2114 worker_thread+0xdc/0x1000 kernel/workqueue.c:2248 kthread+0x348/0x420 kernel/kthread.c:232 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:402 INFO: task syz-executor3:1856 blocked for more than 140 seconds. Not tainted 4.14.68+ #4 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor3 D27144 1856 1 0x00000004 Call Trace: schedule+0x7f/0x1b0 kernel/sched/core.c:3490 schedule_timeout+0x710/0xe60 kernel/time/timer.c:1718 do_wait_for_common kernel/sched/completion.c:91 [inline] __wait_for_common kernel/sched/completion.c:112 [inline] wait_for_common+0x3bc/0x4e0 kernel/sched/completion.c:123 __wait_rcu_gp+0x250/0x3a0 kernel/rcu/update.c:413 synchronize_rcu.part.43+0xd2/0xe0 kernel/rcu/tree_plugin.h:764 namespace_unlock+0xef/0x110 fs/namespace.c:1466 do_umount fs/namespace.c:1662 [inline] SYSC_umount fs/namespace.c:1757 [inline] SyS_umount+0x5e1/0xc10 fs/namespace.c:1726 do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x459aa7 RSP: 002b:00007ffdc6152248 EFLAGS: 00000206 ORIG_RAX: 00000000000000a6 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000459aa7 RDX: 0000000000408450 RSI: 0000000000000002 RDI: 00007ffdc61522f0 RBP: 0000000000000435 R08: 0000000000000000 R09: 000000000000000b R10: 0000000000000005 R11: 0000000000000206 R12: 00007ffdc6153350 R13: 0000000001cae940 R14: 0000000000000000 R15: badc0ffeebadface Showing all locks held in the system: 3 locks held by kworker/u4:0/5: #0: ("%s""netns"){+.+.}, at: [] process_one_work+0x787/0x15c0 kernel/workqueue.c:2085 #1: (net_cleanup_work){+.+.}, at: [] process_one_work+0x7bf/0x15c0 kernel/workqueue.c:2089 #2: (rcu_preempt_state.barrier_mutex){+.+.}, at: [] _rcu_barrier+0x5b/0x3f0 kernel/rcu/tree.c:3529 1 lock held by khungtaskd/23: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x74/0x20f kernel/locking/lockdep.c:4541 2 locks held by getty/1763: #0: (&tty->ldisc_sem){++++}, at: [] tty_ldisc_ref_wait+0x20/0x80 drivers/tty/tty_ldisc.c:275 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1ff/0x15e0 drivers/tty/n_tty.c:2142 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 23 Comm: khungtaskd Not tainted 4.14.68+ #4 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xb9/0x11b lib/dump_stack.c:53 nmi_cpu_backtrace.cold.0+0x47/0x85 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x121/0x146 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:196 [inline] watchdog+0x574/0xa70 kernel/hung_task.c:252 kthread+0x348/0x420 kernel/kthread.c:232 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:402 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 14381 Comm: syz-executor6 Not tainted 4.14.68+ #4 task: ffff8801a0355e00 task.stack: ffff88019f358000 RIP: 0033:0x4023cb RSP: 002b:00007f613b802690 EFLAGS: 00000206 RAX: 0000000004a7b081 RBX: 0000000000000007 RCX: 0000000000457099 RDX: 0000000000000000 RSI: 00007f613b8026c0 RDI: 0000000000000007 RBP: 00000000009300a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000004d7008 R14: 00000000004ca112 R15: 0000000000000000 FS: 00007f613b803700(0000) GS:ffff8801dba00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f9c40ae9518 CR3: 00000001d6f00004 CR4: 00000000001606b0 DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600