INFO: task syz.9.3937:20305 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.9.3937      state:D stack:26832 pid:20305 ppid: 15494 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11c3/0x4350 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
 __mutex_lock_common+0xdf5/0x2400 kernel/locking/mutex.c:669
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 tty_release_struct+0xaa/0xd0 drivers/tty/tty_io.c:1718
 tty_release+0xc29/0x1630 drivers/tty/tty_io.c:1880
 __fput+0x212/0x8c0 fs/file_table.c:311
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0x635/0x2110 kernel/exit.c:890
 do_group_exit+0x12c/0x2f0 kernel/exit.c:1004
 get_signal+0x7eb/0x12e0 kernel/signal.c:2913
 arch_do_signal_or_restart+0xe6/0x12a0 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:157 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:217
 __syscall_exit_to_user_mode_work kernel/entry/common.c:299 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:310
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f1fd2c0c199
RSP: 002b:00007f1fd0e43028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffed RBX: 00007f1fd2e94090 RCX: 00007f1fd2c0c199
RDX: 00002000000000c0 RSI: 0000000000008923 RDI: 0000000000000008
RBP: 00007f1fd2ca3888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1fd2e94128 R14: 00007f1fd2e94090 R15: 00007ffc637620a8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
 #0: ffffffff8d11efa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3945:
 #0: ffff88802aaf2098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: ffffc90002cf62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x594/0x1a50 drivers/tty/n_tty.c:2158
4 locks held by kworker/u4:4/13007:
2 locks held by kworker/u4:8/19345:
1 lock held by syz.9.3937/20305:
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: tty_release_struct+0xaa/0xd0 drivers/tty/tty_io.c:1718
3 locks held by syz.7.3941/20311:
1 lock held by syz.2.3943/20329:
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd2/0x2c0 drivers/tty/pty.c:823
1 lock held by syz.5.3985/20585:
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd2/0x2c0 drivers/tty/pty.c:823
1 lock held by syz.1.3978/20690:
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd2/0x2c0 drivers/tty/pty.c:823
1 lock held by syz.4.4007/20789:
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2064 [inline]
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x20a/0xcd0 drivers/tty/tty_io.c:2148
1 lock held by syz.6.4067/21090:
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: ptmx_open+0xd2/0x2c0 drivers/tty/pty.c:823
1 lock held by syz-executor/21348:
1 lock held by syz.8.4137/21385:
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2064 [inline]
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x20a/0xcd0 drivers/tty/tty_io.c:2148
1 lock held by syz.9.4161/21490:
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2064 [inline]
 #0: ffffffff8d7f6648 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x20a/0xcd0 drivers/tty/tty_io.c:2148
6 locks held by syz.7.4424/22490:
 #0: ffffffff8e1bae68 (register_mutex#4){+.+.}-{3:3}, at: odev_release+0x4a/0x70 sound/core/seq/oss/seq_oss.c:143
 #1: ffff888061c9bcb8 (&mdev->open_mutex){+.+.}-{3:3}, at: snd_seq_oss_midi_close+0x193/0x6c0 sound/core/seq/oss/seq_oss_midi.c:404
 #2: ffff8880783b20f0 (&grp->list_mutex#2){+.+.}-{3:3}, at: delete_and_unsubscribe_port sound/core/seq/seq_ports.c:548 [inline]
 #2: ffff8880783b20f0 (&grp->list_mutex#2){+.+.}-{3:3}, at: snd_seq_port_disconnect+0x596/0x660 sound/core/seq/seq_ports.c:627
 #3: ffff88802004b168 (&rmidi->open_mutex){+.+.}-{3:3}, at: rawmidi_release_priv+0x43/0x170 sound/core/rawmidi.c:541
 #4: ffff888028144940 (&umidi->disc_rwsem){.+.+}-{3:3}, at: substream_open+0x70/0x730 sound/usb/midi.c:1157
 #5: ffff8880281449d0 (&umidi->mutex){+.+.}-{3:3}, at: substream_open+0xd7/0x730 sound/usb/midi.c:1163
1 lock held by sed/22500:

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

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
 watchdog+0xe1b/0xe60 kernel/hung_task.c:369
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>