syzbot

INFO: task syz.0.17:6097 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:26728 pid:6097  tgid:6097  ppid:6001   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x16f3/0x4c20 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7026
 schedule_timeout+0x9a/0x270 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:100 [inline]
 __wait_for_common kernel/sched/completion.c:121 [inline]
 wait_for_common kernel/sched/completion.c:132 [inline]
 wait_for_completion+0x2bf/0x5d0 kernel/sched/completion.c:153
 __vhost_worker_flush+0x148/0x1e0 drivers/vhost/vhost.c:296
 vhost_worker_flush drivers/vhost/vhost.c:303 [inline]
 vhost_dev_flush+0xb2/0x130 drivers/vhost/vhost.c:313
 vhost_vsock_flush drivers/vhost/vsock.c:698 [inline]
 vhost_vsock_dev_release+0x22b/0x450 drivers/vhost/vsock.c:750
 __fput+0x45b/0xa80 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop+0xe9/0x130 kernel/entry/common.c:43
 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/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9258c9efc9
RSP: 002b:00007ffc47c13e48 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f9258ef7da0 RCX: 00007f9258c9efc9
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f9258ef7da0 R08: 0000000000000000 R09: 0000000847c1413f
R10: 00007f9258ef7cb0 R11: 0000000000000246 R12: 00000000000350f6
R13: 00007ffc47c13f40 R14: ffffffffffffffff R15: 00007ffc47c13f60
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/38:
 #0: ffffffff8d5aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8d5aa4c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #0: ffffffff8d5aa4c0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
6 locks held by kworker/u9:0/61:
2 locks held by getty/5563:
 #0: ffff88823bf3a0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003e8b2e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x444/0x1400 drivers/tty/n_tty.c:2222

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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:332 [inline]
 watchdog+0xf60/0xfa0 kernel/hung_task.c:495
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 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: 61 Comm: kworker/u9:0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: hci2 hci_conn_timeout
RIP: 0010:__bfs kernel/locking/lockdep.c:1815 [inline]
RIP: 0010:__bfs_backwards kernel/locking/lockdep.c:1860 [inline]
RIP: 0010:check_irq_usage kernel/locking/lockdep.c:2796 [inline]
RIP: 0010:check_prev_add kernel/locking/lockdep.c:3169 [inline]
RIP: 0010:check_prevs_add kernel/locking/lockdep.c:3284 [inline]
RIP: 0010:validate_chain+0xfd7/0x2140 kernel/locking/lockdep.c:3908
Code: 25 ff 0f 00 00 39 05 14 a4 0d 11 73 06 89 05 0c a4 0d 11 49 8b 04 24 48 89 de 48 39 e8 0f 84 33 fe ff ff 4c 89 68 30 48 8b 00 <48> 39 e8 75 f4 48 89 de e9 1f fe ff ff 48 c7 c7 f0 a7 47 8d 48 89
RSP: 0018:ffffc9000127f348 EFLAGS: 00000002
RAX: ffffffff95473168 RBX: 00000000000003cd RCX: 0000000000000212
RDX: 0000000000000008 RSI: 00000000000003cd RDI: ffff888019729e00
RBP: ffffffff924b41c8 R08: ffffc9000127f310 R09: 0000000000000020
R10: dffffc0000000000 R11: ffffffff819c5eb0 R12: ffffffff952d9c78
R13: ffffffff952e6698 R14: ffff88801972aa78 R15: 0000000000000211
FS:  0000000000000000(0000) GS:ffff888126efc000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005647ee4f1168 CR3: 0000000037ada000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5237
 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5868
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
 update_cfs_rq_load_avg kernel/sched/fair.c:4569 [inline]
 update_load_avg+0x219/0x1880 kernel/sched/fair.c:4728
 enqueue_entity kernel/sched/fair.c:5261 [inline]
 enqueue_task_fair+0x2d2/0x27f0 kernel/sched/fair.c:6976
 enqueue_task+0x75/0x420 kernel/sched/core.c:2092
 activate_task kernel/sched/core.c:2134 [inline]
 ttwu_do_activate+0x1f3/0x870 kernel/sched/core.c:3706
 ttwu_queue kernel/sched/core.c:3969 [inline]
 try_to_wake_up+0x721/0x12b0 kernel/sched/core.c:4293
 kick_pool+0x47d/0x640 kernel/workqueue.c:1285
 __queue_work+0xd70/0x1010 kernel/workqueue.c:2342
 queue_work_on+0x181/0x270 kernel/workqueue.c:2392
 queue_work include/linux/workqueue.h:669 [inline]
 hci_cmd_sync_submit+0x285/0x2b0 net/bluetooth/hci_sync.c:727
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>