INFO: task syz-executor4:14734 blocked for more than 140 seconds. Not tainted 4.9.128+ #41 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor4 D28504 14734 2105 0x00000004 ffff8801c7b54740 ffff8801a5135280 ffff8801a5135280 ffff8801d5e9c740 ffff8801db621018 ffff8801caaf7bd8 ffffffff8277ee02 0000000000000000 ffff8801c7b54ff0 ffffed0038f6a9fd 00ff8801c7b54740 ffff8801db6218f0 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3553 [] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586 [] __mutex_lock_common kernel/locking/mutex.c:582 [inline] [] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621 [] copy_net_ns+0x155/0x290 net/core/net_namespace.c:406 [] create_new_namespaces+0x501/0x760 kernel/nsproxy.c:106 [] unshare_nsproxy_namespaces+0xa5/0x1d0 kernel/nsproxy.c:205 [] SYSC_unshare kernel/fork.c:2263 [inline] [] SyS_unshare+0x319/0x710 kernel/fork.c:2213 [] do_syscall_64+0x19f/0x480 arch/x86/entry/common.c:282 [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb Showing all locks held in the system: 2 locks held by khungtaskd/24: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x11c/0xa20 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336 2 locks held by getty/2020: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+...}, at: [] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142 2 locks held by syz-executor2/9541: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+...}, at: [] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142 1 lock held by syz-executor4/14734: #0: (net_mutex){+.+.+.}, at: [] copy_net_ns+0x155/0x290 net/core/net_namespace.c:406 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 24 Comm: khungtaskd Not tainted 4.9.128+ #41 ffff8801d9907d08 ffffffff81af2469 0000000000000000 0000000000000000 0000000000000000 0000000000000001 ffffffff810967d0 ffff8801d9907d40 ffffffff81afd1c9 0000000000000000 0000000000000000 0000000000000003 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] nmi_cpu_backtrace.cold.0+0x48/0x87 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x12c/0x151 lib/nmi_backtrace.c:60 [] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog+0x6ad/0xa20 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff8278cb16