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:
 [<ffffffff8278032f>] schedule+0x7f/0x1b0 kernel/sched/core.c:3553
 [<ffffffff82780cb3>] schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3586
 [<ffffffff82782936>] __mutex_lock_common kernel/locking/mutex.c:582 [inline]
 [<ffffffff82782936>] mutex_lock_nested+0x326/0x870 kernel/locking/mutex.c:621
 [<ffffffff8226b0d5>] copy_net_ns+0x155/0x290 net/core/net_namespace.c:406
 [<ffffffff81141491>] create_new_namespaces+0x501/0x760 kernel/nsproxy.c:106
 [<ffffffff81141c85>] unshare_nsproxy_namespaces+0xa5/0x1d0 kernel/nsproxy.c:205
 [<ffffffff810d8509>] SYSC_unshare kernel/fork.c:2263 [inline]
 [<ffffffff810d8509>] SyS_unshare+0x319/0x710 kernel/fork.c:2213
 [<ffffffff8100554f>] do_syscall_64+0x19f/0x480 arch/x86/entry/common.c:282
 [<ffffffff8278df13>] 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: [<ffffffff8130a0ac>] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline]
 #0:  (rcu_read_lock){......}, at: [<ffffffff8130a0ac>] watchdog+0x11c/0xa20 kernel/hung_task.c:239
 #1:  (tasklist_lock){.+.+..}, at: [<ffffffff813e71ec>] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4336
2 locks held by getty/2020:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8278bfd2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81cdee72>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
2 locks held by syz-executor2/9541:
 #0:  (&tty->ldisc_sem){++++++}, at: [<ffffffff8278bfd2>] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367
 #1:  (&ldata->atomic_read_lock){+.+...}, at: [<ffffffff81cdee72>] n_tty_read+0x202/0x16e0 drivers/tty/n_tty.c:2142
1 lock held by syz-executor4/14734:
 #0:  (net_mutex){+.+.+.}, at: [<ffffffff8226b0d5>] 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:
 [<ffffffff81af2469>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81af2469>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81afd1c9>] nmi_cpu_backtrace.cold.0+0x48/0x87 lib/nmi_backtrace.c:99
 [<ffffffff81afd15c>] nmi_trigger_cpumask_backtrace+0x12c/0x151 lib/nmi_backtrace.c:60
 [<ffffffff810968d4>] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37
 [<ffffffff8130a63d>] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline]
 [<ffffffff8130a63d>] check_hung_task kernel/hung_task.c:125 [inline]
 [<ffffffff8130a63d>] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline]
 [<ffffffff8130a63d>] watchdog+0x6ad/0xa20 kernel/hung_task.c:239
 [<ffffffff8113e00d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff8278e0dc>] 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