INFO: task syz.2.1307:10163 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.2.1307 state:D stack:27912 pid:10163 ppid:5772 flags:0x00004004
Call Trace:
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: 0033:0x7f80a8b9e019
RSP: 002b:00007f80a9a3c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f80a8e25fa0 RCX: 00007f80a8b9e019
RDX: 0000000000000001 RSI: 0000200000000240 RDI: 0000000000000004
RBP: 00007f80a8c3500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f80a8e26038 R14: 00007f80a8e25fa0 R15: 00007ffc05172da8
Showing all locks held in the system:
1 lock held by khungtaskd/29:
#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 getty/5529:
#0: ffff888031aba0a0 (&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
3 locks held by syz.3.1197/9872:
#0: ffff88807d6e8ac8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff88805725c418 (sb_writers#16){.+.+}-{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.2.1307/10163:
#0: ffff888017cecac8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
#1: ffff88807c072418 (sb_writers#16){.+.+}-{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 kworker/0:4/10521:
#0: ffff8880196bb938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#0: ffff8880196bb938 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#1: ffffc9000ccefd00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:2632 [inline]
#1: ffffc9000ccefd00 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x975/0x1600 kernel/workqueue.c:2734
#2: ffff8880251801d8 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:1094 [inline]
#2: ffff8880251801d8 (&dev->mutex){....}-{3:3}, at: hub_event+0x188/0x4a80 drivers/usb/core/hub.c:5861
#3: ffff888025183558 (&port_dev->status_lock){+.+.}-{3:3}, at: usb_lock_port drivers/usb/core/hub.c:3215 [inline]
#3: ffff888025183558 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect drivers/usb/core/hub.c:5426 [inline]
#3: ffff888025183558 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_port_connect_change drivers/usb/core/hub.c:5669 [inline]
#3: ffff888025183558 (&port_dev->status_lock){+.+.}-{3:3}, at: port_event drivers/usb/core/hub.c:5833 [inline]
#3: ffff888025183558 (&port_dev->status_lock){+.+.}-{3:3}, at: hub_event+0x2270/0x4a80 drivers/usb/core/hub.c:5915
#4: ffff888024e34a68 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_port_connect drivers/usb/core/hub.c:5427 [inline]
#4: ffff888024e34a68 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_port_connect_change drivers/usb/core/hub.c:5669 [inline]
#4: ffff888024e34a68 (hcd->address0_mutex){+.+.}-{3:3}, at: port_event drivers/usb/core/hub.c:5833 [inline]
#4: ffff888024e34a68 (hcd->address0_mutex){+.+.}-{3:3}, at: hub_event+0x229b/0x4a80 drivers/usb/core/hub.c:5915
#5: ffffffff8dcde390 (ehci_cf_port_reset_rwsem){.+.+}-{3:3}, at: hub_port_reset+0x14d/0x15f0 drivers/usb/core/hub.c:3030
=============================================
NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Tainted: G S syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
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