INFO: task syz.2.398:7189 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.2.398 state:D stack:25728 pid:7189 tgid:7177 ppid:5618 task_flags:0x400140 flags:0x00080002
Call Trace:
context_switch kernel/sched/core.c:5581 [inline]
__schedule+0x1b47/0x5b40 kernel/sched/core.c:7384
__schedule_loop kernel/sched/core.c:7461 [inline]
schedule+0x164/0x2b0 kernel/sched/core.c:7476
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7533
__mutex_lock_common kernel/locking/mutex.c:726 [inline]
__mutex_lock+0x7c4/0x15a0 kernel/locking/mutex.c:821
nbd_start_device_ioctl drivers/block/nbd.c:1604 [inline]
__nbd_ioctl drivers/block/nbd.c:1664 [inline]
nbd_ioctl+0xae0/0xe50 drivers/block/nbd.c:1704
blkdev_ioctl+0x5e3/0x740 block/ioctl.c:798
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fde2899e159
RSP: 002b:00007fde29801028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fde28c26090 RCX: 00007fde2899e159
RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003
RBP: 00007fde28a3506b R08: 0000000000000000 R09: 0000000000000000
RBP: 00007fde28a3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fde28c26128 R14: 00007fde28c26090 R15: 00007ffef01319f8
INFO: task syz.2.398:7195 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.2.398 state:D stack:28808 pid:7195 tgid:7177 ppid:5618 task_flags:0x480140 flags:0x00080002
Call Trace:
context_switch kernel/sched/core.c:5581 [inline]
__schedule+0x1b47/0x5b40 kernel/sched/core.c:7384
__schedule_loop kernel/sched/core.c:7461 [inline]
schedule+0x164/0x2b0 kernel/sched/core.c:7476
blk_mq_freeze_queue_wait+0xfc/0x180 block/blk-mq.c:191
blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline]
queue_limits_commit_update_frozen+0x55/0xd0 block/blk-settings.c:598
nbd_set_size+0x4c5/0x7d0 drivers/block/nbd.c:383
__nbd_ioctl drivers/block/nbd.c:-1 [inline]
nbd_ioctl+0x635/0xe50 drivers/block/nbd.c:1704
blkdev_ioctl+0x5e3/0x740 block/ioctl.c:798
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:597 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fde2899e159
RSP: 002b:00007fde297e0028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fde28c26180 RCX: 00007fde2899e159
RDX: 000000000000007f RSI: 000000000000ab02 RDI: 0000000000000003
RBP: 00007fde28a3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fde28c26218 R14: 00007fde28c26180 R15: 00007ffef01319f8
Showing all locks held in the system:
locks held by khungtaskd/34: 1, last CPU#0:
#0: ffffffff8f15c520 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#0: ffffffff8f15c520 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#0: ffffffff8f15c520 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6871
locks held by kworker/1:2/1560: 5, on CPU#1:
#0: ffff888022ac5d48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#0: ffff888022ac5d48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#0: ffff888022ac5d48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3460 [inline]
#0: ffff888022ac5d48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3578
#1: ffffc90006077c40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#1: ffffc90006077c40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#1: ffffc90006077c40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3460 [inline]
#1: ffffc90006077c40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3578
#2: ffff8880290b21d8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1104 [inline]
#2: ffff8880290b21d8 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4d30 drivers/usb/core/hub.c:5917
#3: ffff88807ec921d8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1104 [inline]
#3: ffff88807ec921d8 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x450 drivers/base/dd.c:1073
#4: ffff8880325431a0 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1104 [inline]
#4: ffff8880325431a0 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x450 drivers/base/dd.c:1073
locks held by getty/5368: 2, on CPU#1:
#0: ffff8880332dc0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc900032332e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 drivers/tty/n_tty.c:2211
locks held by udevd/5616: 1, on CPU#0:
#0: ffff888026c7d350 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0xde/0xd70 block/bdev.c:990
locks held by kworker/1:4/5691: 6, on CPU#1:
#0: ffff888022ac5d48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#0: ffff888022ac5d48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#0: ffff888022ac5d48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3460 [inline]
#0: ffff888022ac5d48 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3578
#1: ffffc9000475fc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#1: ffffc9000475fc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#1: ffffc9000475fc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3460 [inline]
#1: ffffc9000475fc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3578
#2: ffff8880299ca1d8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1104 [inline]
#2: ffff8880299ca1d8 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4d30 drivers/usb/core/hub.c:5917
#3: ffff888029db3568 (&port_dev->status_lock){+.+.}-{4:4}, at: usb_lock_port drivers/usb/core/hub.c:3270 [inline]
#3: ffff888029db3568 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_port_connect drivers/usb/core/hub.c:5482 [inline]
#3: ffff888029db3568 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_port_connect_change drivers/usb/core/hub.c:5725 [inline]
#3: ffff888029db3568 (&port_dev->status_lock){+.+.}-{4:4}, at: port_event drivers/usb/core/hub.c:5889 [inline]
#3: ffff888029db3568 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_event+0x20a1/0x4d30 drivers/usb/core/hub.c:5971
#4: ffff8880292eba60 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_port_connect drivers/usb/core/hub.c:5483 [inline]
#4: ffff8880292eba60 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_port_connect_change drivers/usb/core/hub.c:5725 [inline]
#4: ffff8880292eba60 (hcd->address0_mutex){+.+.}-{4:4}, at: port_event drivers/usb/core/hub.c:5889 [inline]
#4: ffff8880292eba60 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_event+0x20c9/0x4d30 drivers/usb/core/hub.c:5971
#5: ffffffff8ff1b588 (ehci_cf_port_reset_rwsem){.+.+}-{4:4}, at: hub_port_reset+0x14d/0x1810 drivers/usb/core/hub.c:3085
locks held by kworker/0:5/5719: 2, last CPU#0:
#0: ffff88813fe09d48 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#0: ffff88813fe09d48 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#0: ffff88813fe09d48 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3460 [inline]
#0: ffff88813fe09d48 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3578
#1: ffffc90004cffc40 ((work_completion)(&(&tbl->gc_work)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
#1: ffffc90004cffc40 ((work_completion)(&(&tbl->gc_work)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#1: ffffc90004cffc40 ((work_completion)(&(&tbl->gc_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3460 [inline]
#1: ffffc90004cffc40 ((work_completion)(&(&tbl->gc_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3578
locks held by syz.2.398/7189: 1, on CPU#1:
#0: ffff888026c67a60 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_start_device_ioctl drivers/block/nbd.c:1604 [inline]
#0: ffff888026c67a60 (&nbd->config_lock){+.+.}-{4:4}, at: __nbd_ioctl drivers/block/nbd.c:1664 [inline]
#0: ffff888026c67a60 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_ioctl+0xae0/0xe50 drivers/block/nbd.c:1704
locks held by syz.2.398/7195: 4, on CPU#1:
#0: ffff888026c67a60 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_ioctl+0x133/0xe50 drivers/block/nbd.c:1697
#1: ffff88802673b528 (&q->limits_lock){+.+.}-{4:4}, at: queue_limits_start_update include/linux/blkdev.h:1104 [inline]
#1: ffff88802673b528 (&q->limits_lock){+.+.}-{4:4}, at: nbd_set_size+0x284/0x7d0 drivers/block/nbd.c:375
#2: ffff88802673aef0 (&q->q_usage_counter(io)#51){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline]
#2: ffff88802673aef0 (&q->q_usage_counter(io)#51){++++}-{0:0}, at: queue_limits_commit_update_frozen+0x55/0xd0 block/blk-settings.c:598
#3: ffff88802673af28 (&q->q_usage_counter(queue)#35){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline]
#3: ffff88802673af28 (&q->q_usage_counter(queue)#35){+.+.}-{0:0}, at: queue_limits_commit_update_frozen+0x55/0xd0 block/blk-settings.c:598
locks held by syz.0.787/8711: 1, on CPU#0:
#0: ffff888026c7d350 (&disk->open_mutex
){+.+.}-{4:4}, at: sync_bdevs+0x276/0x470 block/bdev.c:1369
locks held by syz.3.1269/10316: 1, last CPU#1:
#0: ffff88813fe33440 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock_killable include/linux/mmap_lock.h:548 [inline]
#0: ffff88813fe33440 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x1dd/0x4e0 mm/util.c:579
=============================================
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 34 Comm: khungtaskd Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:123
nmi_trigger_cpumask_backtrace+0x17d/0x390 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+0x135/0x170 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:377 [inline]
watchdog+0x1058/0x10d0 kernel/hung_task.c:598
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 16 Comm: pr/ttyS0 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:io_serial_in+0x77/0xc0 drivers/tty/serial/8250/8250_port.c:425
Code: e8 ce a5 46 fc 44 89 f9 d3 e3 49 83 c6 40 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 df 72 b8 fc 41 03 1e 89 da ec <0f> b6 c0 5b 41 5c 41 5e 41 5f c3 cc cc cc cc cc 44 89 f9 80 e1 07
RSP: 0018:ffffc900001578b8 EFLAGS: 00000002
RAX: 1ffffffff363d600 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000000 RDI: 0000000000000020
RBP: dffffc0000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: ffffffff85828b30 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff9b1eb0c0 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff888124623000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000002000 CR3: 00000000498d4000 CR4: 00000000003526f0
DR0: 000000000000000c DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
serial_in drivers/tty/serial/8250/8250.h:134 [inline]
serial_lsr_in drivers/tty/serial/8250/8250.h:156 [inline]
wait_for_lsr+0x184/0x2f0 drivers/tty/serial/8250/8250_port.c:2027
serial8250_fifo_wait_for_lsr_thre drivers/tty/serial/8250/8250_port.c:3285 [inline]
__serial8250_console_fifo_write+0xcd/0x3e0 drivers/tty/serial/8250/8250_port.c:3360
serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3393 [inline]
__serial8250_console_write drivers/tty/serial/8250/8250_port.c:3444 [inline]
serial8250_console_write+0xaa1/0x1200 drivers/tty/serial/8250/8250_port.c:3508
nbcon_emit_next_record+0xef5/0x1a90 kernel/printk/nbcon.c:-1
nbcon_emit_one kernel/printk/nbcon.c:1157 [inline]
nbcon_kthread_func+0x6d9/0x8d0 kernel/printk/nbcon.c:1271
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245