INFO: task syz.9.5632:22527 blocked for more than 143 seconds.
      Tainted: G S                 syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.9.5632      state:D stack:25192 pid:22527 ppid:17205  flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:6834
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x673/0xc80 kernel/locking/mutex.c:747
 write_ports+0xb7/0xfa0 fs/nfsd/nfsctl.c:843
 nfsctl_transaction_write+0x10c/0x150 fs/nfsd/nfsctl.c:113
 vfs_write+0x299/0x9a0 fs/read_write.c:582
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f5f6359e019
RSP: 002b:00007f5f644a9028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f5f63825fa0 RCX: 00007f5f6359e019
RDX: 0000000000000002 RSI: 00002000000001c0 RDI: 0000000000000003
RBP: 00007f5f6363500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f5f63826038 R14: 00007f5f63825fa0 R15: 00007ffd99c0fef8
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/u4:1/12:
1 lock held by khungtaskd/28:
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
2 locks held by kworker/u4:6/1084:
 #0: ffff888017c71938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #0: ffff888017c71938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #1: ffffc900046cfd00 ((reaper_work).work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #1: ffffc900046cfd00 ((reaper_work).work){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
3 locks held by kworker/u4:7/1100:
3 locks held by udevd/5142:
2 locks held by getty/5533:
 #0: ffff888020c800a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x428/0x1370 drivers/tty/n_tty.c:2217
2 locks held by kworker/u5:3/5782:
 #0: ffff88802176a538 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #0: ffff88802176a538 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #1: ffffc9000466fd00 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #1: ffffc9000466fd00 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
2 locks held by kworker/u5:0/20314:
 #0: ffff88802176a538 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #0: ffff88802176a538 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
 #1: ffffc9000ba6fd00 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
 #1: ffffc9000ba6fd00 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
3 locks held by syz.8.5357/21621:
 #0: ffff888079a2cd48 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff8880586f2418 (sb_writers#34){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
 #2: ffffffff8d3e1728 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb7/0xfa0 fs/nfsd/nfsctl.c:843
3 locks held by syz.9.5632/22527:
 #0: ffff888020c165c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88806bfa4418 (sb_writers#34){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
 #2: ffffffff8d3e1728 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb7/0xfa0 fs/nfsd/nfsctl.c:843
6 locks held by syz.7.5743/22968:
4 locks held by syz.2.5773/23069:
 #0: ffff888030bb7080 (&iint_mutex_key[depth]){+.+.}-{3:3}, at: process_measurement+0x739/0x1d50 security/integrity/ima/ima_main.c:275
 #1: ffff8880306a0e80 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xa1/0xc50 fs/seq_file.c:182
 #2: ffff888140b93c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_seq_start+0x5d/0x410 fs/kernfs/file.c:172
 #3: ffff888141e58100 (kn->active#102){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #3: ffff888141e58100 (kn->active#102){.+.+}-{0:0}, at: kernfs_seq_start+0xb2/0x410 fs/kernfs/file.c:173
2 locks held by syz-executor/23183:
 #0: ffff88802d9aa0e0 (&type->s_umount_key#92){++++}-{3:3}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88802d9aa0e0 (&type->s_umount_key#92){++++}-{3:3}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88802d9aa0e0 (&type->s_umount_key#92){++++}-{3:3}, at: deactivate_super+0xa4/0xe0 fs/super.c:513
 #1: ffffffff8d3e1728 (nfsd_mutex){+.+.}-{3:3}, at: nfsd_shutdown_threads+0x53/0x1a0 fs/nfsd/nfssvc.c:638
2 locks held by syz.1.5898/23730:
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2044 [inline]
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xcc0 drivers/tty/tty_io.c:2127
 #1: ffff8880252ca1c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_init_dev+0x74/0x4c0 drivers/tty/tty_io.c:1413
1 lock held by syz.6.5922/23829:
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2044 [inline]
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xcc0 drivers/tty/tty_io.c:2127
1 lock held by syz.4.5952/24040:
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd0/0x2c0 drivers/tty/pty.c:823
1 lock held by syz.5.5959/24118:
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd0/0x2c0 drivers/tty/pty.c:823
3 locks held by syz.9.5981/24288:
 #0: ffff888030d325c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff8880246fc418 (sb_writers#34){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
 #2: ffffffff8d3e1728 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb7/0xfa0 fs/nfsd/nfsctl.c:843
1 lock held by syz.2.6008/24573:
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd0/0x2c0 drivers/tty/pty.c:823
1 lock held by syz.3.6041/24732:
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2044 [inline]
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xcc0 drivers/tty/tty_io.c:2127
3 locks held by syz.0.6055/24794:
 #0: ffff88807908f9c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88806c55a418 (sb_writers#34){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
 #2: ffffffff8d3e1728 (nfsd_mutex){+.+.}-{3:3}, at: write_ports+0xb7/0xfa0 fs/nfsd/nfsctl.c:843
1 lock held by syz.1.6081/25067:
 #0: ffff88802d9aa0e0 (&type->s_umount_key#92){++++}-{3:3}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff88802d9aa0e0 (&type->s_umount_key#92){++++}-{3:3}, at: super_lock+0x189/0x390 fs/super.c:117
4 locks held by syz-executor/25095:
1 lock held by syz.4.6125/25429:
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2044 [inline]
 #0: ffffffff8d8b7948 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x211/0xcc0 drivers/tty/tty_io.c:2127

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 28 Comm: khungtaskd Tainted: G S                 syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a6/0x3e0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xf59/0xfa0 kernel/hung_task.c:379
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>