INFO: task syz-executor:5596 blocked for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:22168 pid:5596  tgid:5596  ppid:1      task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5533 [inline]
 __schedule+0x1259/0x6920 kernel/sched/core.c:7284
 __schedule_loop kernel/sched/core.c:7361 [inline]
 schedule+0xdd/0x2c0 kernel/sched/core.c:7376
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7433
 __mutex_lock_common kernel/locking/mutex.c:726 [inline]
 __mutex_lock+0xccb/0x1bd0 kernel/locking/mutex.c:821
 nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:582
 nfsd_umount+0x3b/0x60 fs/nfsd/nfsctl.c:1372
 deactivate_locked_super+0xbd/0x130 fs/super.c:586
 deactivate_super fs/super.c:614 [inline]
 deactivate_super+0xea/0x110 fs/super.c:610
 cleanup_mnt+0xb7/0x160 fs/namespace.c:1392
 task_work_run+0x150/0x240 kernel/task_work.c:233
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 __exit_to_user_mode_loop kernel/entry/common.c:70 [inline]
 exit_to_user_mode_loop+0x1d8/0x700 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:343 [inline]
 do_syscall_64+0x661/0x790 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9eaf99f417
RSP: 002b:00007ffe83f36ca8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f9eafa34ccb RCX: 00007f9eaf99f417
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffe83f36d60
RBP: 00007ffe83f36d60 R08: 00007ffe83f37d60 R09: 00000000ffffffff
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe83f37df0
R13: 00007f9eafa34ccb R14: 000000000008102b R15: 00007ffe83f37e30
 </TASK>

Showing all locks held in the system:
locks held by khungtaskd/32: 1, last CPU#0:
 #0: ffffffff8fdec5a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffffffff8fdec5a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8fdec5a0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6871
locks held by getty/5360: 2, on CPU#0:
 #0: ffff88802a07e0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc900032432e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x14e0 drivers/tty/n_tty.c:2211
locks held by syz-executor/5596: 2, on CPU#0:
 #0: ffff8880373920e8 (&type->s_umount_key#89){+.+.}-{4:4}, at: __super_lock fs/super.c:60 [inline]
 #0: ffff8880373920e8 (&type->s_umount_key#89){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:75 [inline]
 #0: ffff8880373920e8 (&type->s_umount_key#89){+.+.}-{4:4}, at: deactivate_super fs/super.c:613 [inline]
 #0: ffff8880373920e8 (&type->s_umount_key#89){+.+.}-{4:4}, at: deactivate_super+0xe2/0x110 fs/super.c:610
 #1: ffffffff90289ca0 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:582
locks held by syz.2.5683/19048: 3, on CPU#0:
 #0: ffff888076aa5b30 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff888029d3a460 (sb_writers#25){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739
 #2: ffffffff90289ca0 (nfsd_mutex){+.+.}-{4:4}, at: write_ports+0xa5/0xcc0 fs/nfsd/nfsctl.c:867

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 32 Comm: khungtaskd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:123
 nmi_trigger_cpumask_backtrace+0x21f/0x2a0 lib/nmi_backtrace.c:66
 trigger_all_cpu_backtrace include/linux/nmi.h:164 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x141/0x190 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xcb1/0x1030 kernel/hung_task.c:561
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>