syzbot

INFO: task [ 1759.196310][   T38] INFO: task syz.5.1809:13941 blocked for more than 143 seconds.
      Not tainted syzkaller #0
      Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.1809      state:D stack:25448 pid:13941 tgid:13940 ppid:11823  task_flags:0x40044c flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x16f3/0x4c20 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 rt_mutex_schedule+0x77/0xf0 kernel/sched/core.c:7339
 rt_mutex_slowlock_block+0x5ba/0x6d0 kernel/locking/rtmutex.c:1647
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1721 [inline]
 __rt_mutex_slowlock_locked kernel/locking/rtmutex.c:1760 [inline]
 rt_mutex_slowlock+0x2b1/0x6e0 kernel/locking/rtmutex.c:1800
 __rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
 __mutex_lock_common kernel/locking/rtmutex_api.c:536 [inline]
 mutex_lock_nested+0x16a/0x1d0 kernel/locking/rtmutex_api.c:547
 device_lock include/linux/device.h:911 [inline]
 usbdev_release+0x7f/0x740 drivers/usb/core/devio.c:1099
 __fput+0x458/0xa80 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x6b5/0x2300 kernel/exit.c:961
 do_group_exit+0x21c/0x2d0 kernel/exit.c:1102
 get_signal+0x125e/0x1310 kernel/signal.c:3034
 arch_do_signal_or_restart+0x9a/0x750 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x75/0x110 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x2bd/0x3b0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4f0ea4d510
RSP: 002b:00007f4f0ccb5b70 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
RAX: 0000000000000003 RBX: 0000000000101301 RCX: 00007f4f0ea4d510
RDX: 0000000000101301 RSI: 00007f4f0ccb5c10 RDI: 00000000ffffff9c
RBP: 00007f4f0ccb5c10 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: cccccccccccccccd
R13: 00007f4f0ec96038 R14: 00007f4f0ec95fa0 R15: 00007ffc69845658
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/38:
 #0: ffffffff8d9a8d80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8d9a8d80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8d9a8d80 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
4 locks held by kworker/u8:3/57:
 #0: ffff88801a6f4138 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
 #0: ffff88801a6f4138 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3319
 #1: ffffc9000123fbc0 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
 #1: ffffc9000123fbc0 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3319
 #2: ffffffff8ecc6840 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xf7/0x800 net/core/net_namespace.c:658
 #3: ffffffff8d9ae730 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x4c/0x570 kernel/rcu/tree.c:3815
5 locks held by kworker/u8:5/70:
5 locks held by kworker/u8:6/160:
6 locks held by kworker/0:2/1229:
 #0: ffff888141291138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
 #0: ffff888141291138 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3319
 #1: ffffc90005097bc0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
 #1: ffffc90005097bc0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3319
 #2: ffff888027b85188 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:911 [inline]
 #2: ffff888027b85188 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4a20 drivers/usb/core/hub.c:5898
 #3: ffff88806ba90188 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:911 [inline]
 #3: ffff88806ba90188 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x400 drivers/base/dd.c:1006
 #4: ffff888027b14150 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:911 [inline]
 #4: ffff888027b14150 (&dev->mutex){....}-{4:4}, at: __device_attach+0x88/0x400 drivers/base/dd.c:1006
 #5: ffffffff8d851160 (umhelper_sem){++++}-{4:4}, at: usermodehelper_read_trylock+0xf0/0x2b0 kernel/umh.c:214
5 locks held by kworker/u8:8/1441:
2 locks held by getty/5596:
 #0: ffff88823bf280a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003e832e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x444/0x1410 drivers/tty/n_tty.c:2222
3 locks held by kworker/0:8/8548:
 #0: ffff888019898538 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
 #0: ffff888019898538 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3319
 #1: ffffc900043ffbc0 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
 #1: ffffc900043ffbc0 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3319
 #2: ffff88805daad260 (&data->fib_lock){+.+.}-{4:4}, at: nsim_fib_event_work+0x2ac/0x31b0 drivers/net/netdevsim/fib.c:1490
5 locks held by kworker/u8:16/12697:
4 locks held by udevd/13386:
 #0: ffff88805cf9f608 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xb8/0xe10 fs/seq_file.c:182
 #1: ffff88803364cc78 (&of->mutex#2){+.+.}-{4:4}, at: kernfs_seq_start+0x5c/0x420 fs/kernfs/file.c:172
 #2: ffff88805d5ef698 (kn->active#19){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff88805d5ef698 (kn->active#19){.+.+}-{0:0}, at: kernfs_seq_start+0xb2/0x420 fs/kernfs/file.c:173
 #3: ffff88806ba90188 (&dev->mutex){....}-{4:4}, at: device_lock_interruptible include/linux/device.h:916 [inline]
 #3: ffff88806ba90188 (&dev->mutex){....}-{4:4}, at: manufacturer_show+0x26/0xa0 drivers/usb/core/sysfs.c:142
1 lock held by syz.5.1809/13941:
 #0: ffff888027b85188 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:911 [inline]
 #0: ffff888027b85188 (&dev->mutex){....}-{4:4}, at: usbdev_release+0x7f/0x740 drivers/usb/core/devio.c:1099
7 locks held by syz-executor/15083:
4 locks held by syz-executor/15107:
 #0: ffff888034d34488 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:3108 [inline]
 #0: ffff888034d34488 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x217/0xb40 fs/read_write.c:682
 #1: ffff888052071478 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1df/0x540 fs/kernfs/file.c:343
 #2: ffff888026503d28 (kn->active#52){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #2: ffff888026503d28 (kn->active#52){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x232/0x540 fs/kernfs/file.c:344
 #3: ffffffff8e542e78 (nsim_bus_dev_list_lock){+.+.}-{4:4}, at: del_device_store+0xd1/0x360 drivers/net/netdevsim/bus.c:234
3 locks held by syz-executor/15155:
 #0: ffffffff8f1d7ae8 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8f1d7ae8 (&ops->srcu#2){.+.+}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8f1d7ae8 (&ops->srcu#2){.+.+}-{0:0}, at: rtnl_link_ops_get+0x23/0x250 net/core/rtnetlink.c:570
 #1: ffffffff8ecd3738 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
 #1: ffffffff8ecd3738 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:341 [inline]
 #1: ffffffff8ecd3738 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0x8db/0x1c70 net/core/rtnetlink.c:4056
 #2: ffffffff8d852638 (wq_pool_mutex){+.+.}-{4:4}, at: apply_wqattrs_lock kernel/workqueue.c:5179 [inline]
 #2: ffffffff8d852638 (wq_pool_mutex){+.+.}-{4:4}, at: __alloc_workqueue+0x9ef/0x1b70 kernel/workqueue.c:5734
2 locks held by syz-executor/15207:
1 lock held by syz.7.2087/15212:

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:328 [inline]
 watchdog+0xf93/0xfe0 kernel/hung_task.c:491
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 17 Comm: pr/legacy Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:io_serial_out+0x7c/0xc0 drivers/tty/serial/8250/8250_port.c:407
Code: 3f 7f fc 44 89 f9 d3 e5 49 83 ee 80 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 3c 86 de fc 41 03 2e 89 d8 89 ea ee <5b> 41 5c 41 5e 41 5f 5d c3 cc cc cc cc cc 44 89 f9 80 e1 07 38 c1
RSP: 0018:ffffc900001678f0 EFLAGS: 00000202
RAX: 0000000000000038 RBX: 0000000000000038 RCX: 0000000000000000
RDX: 00000000000003f8 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00000000000003f8 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffffff853f2e20 R12: dffffc0000000000
R13: 0000000000000001 R14: ffffffff993ae620 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881268bc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000002ae030 CR3: 000000006ff1a000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 serial_port_out include/linux/serial_core.h:798 [inline]
 serial8250_console_putchar drivers/tty/serial/8250/8250_port.c:3246 [inline]
 serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:-1 [inline]
 serial8250_console_write+0x128e/0x1b40 drivers/tty/serial/8250/8250_port.c:3396
 console_emit_next_record kernel/printk/printk.c:3118 [inline]
 console_flush_all+0x695/0xcd0 kernel/printk/printk.c:3226
 __console_flush_and_unlock+0xa4/0x240 kernel/printk/printk.c:3285
 legacy_kthread_func+0x13b/0x1a0 kernel/printk/printk.c:3638
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>