syzbot

INFO: task kworker/u8:10:1307 blocked for more than 144 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this mes[ 1342.146675][   T38] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:10   state:D stack:21280 pid:1307  tgid:1307  ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: netns cleanup_net
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5298 [inline]
 __schedule+0x1553/0x5240 kernel/sched/core.c:6911
 __schedule_loop kernel/sched/core.c:6993 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7008
 rxrpc_destroy_all_calls+0x44e/0x570 net/rxrpc/call_object.c:752
 rxrpc_exit_net+0x6f/0xc0 net/rxrpc/net_ns.c:112
 ops_exit_list net/core/net_namespace.c:199 [inline]
 ops_undo_list+0x49f/0x940 net/core/net_namespace.c:252
 cleanup_net+0x56e/0x800 net/core/net_namespace.c:702
 process_one_work kernel/workqueue.c:3288 [inline]
 process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3371
 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3452
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/1:0/31:
1 lock held by khungtaskd/38:
 #0: ffffffff8ddcb980 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #0: ffffffff8ddcb980 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #0: ffffffff8ddcb980 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
3 locks held by kworker/u8:10/1307:
 #0: ffff88801aee1138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3263 [inline]
 #0: ffff88801aee1138 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3371
 #1: ffffc90005f37c40 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3264 [inline]
 #1: ffffc90005f37c40 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0 kernel/workqueue.c:3371
 #2: ffffffff8f14ede0 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf4/0x800 net/core/net_namespace.c:673
2 locks held by getty/5556:
 #0: ffff8880376200a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003e762e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x462/0x13c0 drivers/tty/n_tty.c:2211
6 locks held by kworker/1:6/5873:
 #0: ffff8880222c6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3263 [inline]
 #0: ffff8880222c6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3371
 #1: ffffc90004e5fc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3264 [inline]
 #1: ffffc90004e5fc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0 kernel/workqueue.c:3371
 #2: ffff888029e6a210 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:949 [inline]
 #2: ffff888029e6a210 (&dev->mutex){....}-{4:4}, at: hub_event+0x17c/0x4f60 drivers/usb/core/hub.c:5899
 #3: ffff888062470210 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:949 [inline]
 #3: ffff888062470210 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x450 drivers/base/dd.c:1068
 #4: ffff888060e431d8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:949 [inline]
 #4: ffff888060e431d8 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x450 drivers/base/dd.c:1068
 #5: ffff8880445a0f78 (&d->usb_mutex){+.+.}-{4:4}, at: az6027_usb_out_op drivers/media/usb/dvb-usb/az6027.c:340 [inline]
 #5: ffff8880445a0f78 (&d->usb_mutex){+.+.}-{4:4}, at: az6027_frontend_poweron drivers/media/usb/dvb-usb/az6027.c:834 [inline]
 #5: ffff8880445a0f78 (&d->usb_mutex){+.+.}-{4:4}, at: az6027_frontend_attach+0x4b/0x560 drivers/media/usb/dvb-usb/az6027.c:907
6 locks held by kworker/1:4/21667:
 #0: ffff8880222c6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3263 [inline]
 #0: ffff8880222c6138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3371
 #1: ffffc90007abfc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3264 [inline]
 #1: ffffc90007abfc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0 kernel/workqueue.c:3371
 #2: ffff888029db2210 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:949 [inline]
 #2: ffff888029db2210 (&dev->mutex){....}-{4:4}, at: hub_event+0x17c/0x4f60 drivers/usb/core/hub.c:5899
 #3: ffff888029db9640 (&port_dev->status_lock){+.+.}-{4:4}, at: usb_lock_port drivers/usb/core/hub.c:3252 [inline]
 #3: ffff888029db9640 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_port_connect drivers/usb/core/hub.c:5464 [inline]
 #3: ffff888029db9640 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 #3: ffff888029db9640 (&port_dev->status_lock){+.+.}-{4:4}, at: port_event drivers/usb/core/hub.c:5871 [inline]
 #3: ffff888029db9640 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_event+0x21b0/0x4f60 drivers/usb/core/hub.c:5953
 #4: ffff888024be4f58 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_port_connect drivers/usb/core/hub.c:5465 [inline]
 #4: ffff888024be4f58 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 #4: ffff888024be4f58 (hcd->address0_mutex){+.+.}-{4:4}, at: port_event drivers/usb/core/hub.c:5871 [inline]
 #4: ffff888024be4f58 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_event+0x21e0/0x4f60 drivers/usb/core/hub.c:5953
 #5: ffffffff8e9fcaa0 (ehci_cf_port_reset_rwsem){.+.+}-{4:4}, at: hub_port_reset+0x14e/0x1820 drivers/usb/core/hub.c:3067
4 locks held by syz.1.3644/29119:
5 locks held by syz.5.3653/29174:
4 locks held by syz.4.3657/29170:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 38 Comm: khungtaskd Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:161 [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:346 [inline]
 watchdog+0xfd9/0x1030 kernel/hung_task.c:515
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 17 Comm: pr/legacy Tainted: G             L      syzkaller #0 PREEMPT_{RT,(full)} 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:io_serial_in+0x77/0xc0 drivers/tty/serial/8250/8250_port.c:401
Code: e8 ae f5 93 fc 44 89 f9 d3 e3 49 83 ee 80 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 ef 19 fa fc 41 03 1e 89 da ec <0f> b6 c0 5b 41 5c 41 5e 41 5f e9 5a 82 f7 05 cc 44 89 f9 80 e1 07
RSP: 0000:ffffc900001679d0 EFLAGS: 00000202
RAX: 1ffffffff332bb00 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffffff9995dd10 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffffff85308fc0 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff9995da80 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888126432000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000004b000 CR3: 000000000dbba000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 serial_in drivers/tty/serial/8250/8250.h:128 [inline]
 serial_lsr_in drivers/tty/serial/8250/8250.h:150 [inline]
 wait_for_lsr+0x1aa/0x2f0 drivers/tty/serial/8250/8250_port.c:1970
 serial8250_fifo_wait_for_lsr_thre drivers/tty/serial/8250/8250_port.c:3207 [inline]
 serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3272 [inline]
 serial8250_console_write+0x120d/0x1b90 drivers/tty/serial/8250/8250_port.c:3357
 console_emit_next_record kernel/printk/printk.c:3163 [inline]
 console_flush_one_record+0x68b/0xb90 kernel/printk/printk.c:3269
 legacy_kthread_func+0x1b6/0x250 kernel/printk/printk.c:3712
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>