syzbot

INFO: task syz.1.18:6014 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.18        state:D stack:27400 pid:6014  tgid:6014  ppid:5979   task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x1709/0x5530 kernel/sched/core.c:7231
 __schedule_loop kernel/sched/core.c:7308 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7323
 cgroup_lock_and_drain_offline+0x51a/0x650 kernel/cgroup/cgroup.c:3275
 cgroup_lock_and_drain_offline+0x51a/0x650 kernel/cgroup/cgroup.c:3275
 cgroup_kn_lock_live+0x120/0x230 kernel/cgroup/cgroup.c:1715
 cgroup_subtree_control_write+0x4b5/0x1080 kernel/cgroup/cgroup.c:3577
 cgroup_file_write+0x331/0x8f0 kernel/cgroup/cgroup.c:4316
 kernfs_fop_write_iter+0x3a5/0x540 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x61e/0xbb0 fs/read_write.c:687
 ksys_write+0x156/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x17b/0x530 arch/x86/entry/syscall_64.c:85
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb10ae7de99
RSP: 002b:00007ffdf4bef248 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fb10b105fa0 RCX: 00007fb10ae7de99
RDX: 0000000000000005 RSI: 0000200000000040 RDI: 0000000000000005
RBP: 00007fb10af13eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb10b105fac R14: 00007fb10b105fa0 R15: 00007fb10b105fa0
 </TASK>

Showing all locks held in the system:
locks held by khungtaskd/39: 1, last CPU#1:
 #0: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6835
locks held by kworker/u9:0/60: 1, last CPU#0:
 #0: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: process_one_work+0x7fd/0x1480 kernel/workqueue.c:3344
locks held by kworker/u9:1/4916: 5, last CPU#0:
 #0: ffff88803bc7f938 ((wq_completion)hci3#2){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffff88803bc7f938 ((wq_completion)hci3#2){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffff88803bc7f938 ((wq_completion)hci3#2){+.+.}-{0:0}, at: process_one_work+0x7fd/0x1480 kernel/workqueue.c:3344
 #1: ffffc900079b7c60 ((work_completion)(&(&conn->disc_work)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #1: ffffc900079b7c60 ((work_completion)(&(&conn->disc_work)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #1: ffffc900079b7c60 ((work_completion)(&(&conn->disc_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7fd/0x1480 kernel/workqueue.c:3344
 #2: ffff88803ca40870 (&hdev->unregister_lock){+.+.}-{4:4}, at: hci_cmd_sync_submit+0x3c/0x2d0 net/bluetooth/hci_sync.c:708
 #3: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #3: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #3: ffffffff8e3c3880 (rcu_read_lock){....}-{1:3}, at: __queue_work+0x224/0x1120 kernel/workqueue.c:2356
 #4: ffff88802b790b00 (&p->pi_lock){-...}-{2:2}, at: class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:572 [inline]
 #4: ffff88802b790b00 (&p->pi_lock){-...}-{2:2}, at: try_to_wake_up+0x67/0x1430 kernel/sched/core.c:4292
locks held by getty/5357: 2, on CPU#0:
 #0: ffff88823bfde0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc900044cb2e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x460/0x1360 drivers/tty/n_tty.c:2211
locks held by syz.1.18/6014: 2, on CPU#1:
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline]
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683
 #1: ffff88803d11a478 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:336
locks held by syz.2.19/6054: 2, on CPU#0:
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline]
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683
 #1: ffff888045c34478 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:336
locks held by syz.3.20/6093: 2, on CPU#0:
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline]
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683
 #1: ffff88803bdf0878 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:336
locks held by syz.4.21/6138: 2, on CPU#0:
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline]
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683
 #1: ffff88803fe78078 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:336
locks held by syz.5.22/6180: 2, on CPU#0:
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline]
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683
 #1: ffff888045ecb478 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:336
locks held by syz.6.23/6229: 2, on CPU#0:
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline]
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683
 #1: ffff888034f05c78 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:336
locks held by syz.7.24/6272: 2, on CPU#1:
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline]
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683
 #1: ffff888041607078 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:336
locks held by syz.8.25/6316: 2, on CPU#0:
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline]
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683
 #1: ffff88803b9d1078 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:336
locks held by syz.9.26/6365: 2, on CPU#1:
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2731 [inline]
 #0: ffff888038526510 (sb_writers#9){.+.+}-{0:0}, at: vfs_write+0x231/0xbb0 fs/read_write.c:683
 #1: ffff888044639878 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d9/0x540 fs/kernfs/file.c:336

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 39 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:122
 nmi_trigger_cpumask_backtrace+0x17a/0x380 lib/nmi_backtrace.c:65
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [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:353 [inline]
 watchdog+0xfd7/0x1030 kernel/hung_task.c:561
 kthread+0x388/0x470 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
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 4916 Comm: kworker/u9:1 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
Workqueue: hci3 hci_cmd_sync_work
RIP: 0010:__bfs kernel/locking/lockdep.c:1831 [inline]
RIP: 0010:__bfs_backwards kernel/locking/lockdep.c:1876 [inline]
RIP: 0010:check_irq_usage kernel/locking/lockdep.c:2812 [inline]
RIP: 0010:check_prev_add kernel/locking/lockdep.c:3185 [inline]
RIP: 0010:check_prevs_add kernel/locking/lockdep.c:3300 [inline]
RIP: 0010:validate_chain kernel/locking/lockdep.c:3924 [inline]
RIP: 0010:__lock_acquire+0x19ea/0x2e40 kernel/locking/lockdep.c:5254
Code: 2c 7f 28 14 25 ff 0f 00 00 39 05 ed 7e 27 12 73 06 89 05 e5 7e 27 12 48 8b 02 49 89 d8 4c 39 e8 0f 84 30 fe ff ff 4c 89 78 30 <48> 8b 00 4c 39 e8 75 f4 49 89 d8 e9 1c fe ff ff 48 c7 c7 30 0b 29
RSP: 0018:ffffc900079b7338 EFLAGS: 00000006
RAX: ffffffff9665f4d8 RBX: 00000000000003cd RCX: 0000000000000020
RDX: ffffffff964c2cb8 RSI: ffff88803710ac20 RDI: ffff888037109f40
RBP: e219f84f4de569a1 R08: 00000000000003cd R09: 0000000000000020
R10: 0000000000000000 R11: ffffffff81a16ef0 R12: 000000000000001f
R13: ffffffff9369c2d8 R14: ffff88803710ac20 R15: ffffffff964dc088
FS:  0000000000000000(0000) GS:ffff8881259f2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000557fa624b970 CR3: 00000000449d6000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5906
 _raw_spin_lock_nested+0x32/0x50 kernel/locking/spinlock.c:382
 raw_spin_rq_lock_nested+0x2d/0x160 kernel/sched/core.c:667
 raw_spin_rq_lock kernel/sched/sched.h:1664 [inline]
 rq_lock kernel/sched/sched.h:2002 [inline]
 ttwu_queue kernel/sched/core.c:4075 [inline]
 try_to_wake_up+0x6df/0x1430 kernel/sched/core.c:4415
 __queue_work+0xc13/0x1120 kernel/workqueue.c:2446
 queue_work_on+0x106/0x1d0 kernel/workqueue.c:2489
 queue_work include/linux/workqueue.h:699 [inline]
 hci_req_sync_run net/bluetooth/hci_sync.c:143 [inline]
 __hci_cmd_sync_sk+0x50b/0xd50 net/bluetooth/hci_sync.c:172
 __hci_cmd_sync_status_sk net/bluetooth/hci_sync.c:263 [inline]
 hci_disconnect_sync+0x1ec/0x3c0 net/bluetooth/hci_sync.c:5645
 hci_abort_conn_sync+0x14d/0x1190 net/bluetooth/hci_sync.c:-1
 hci_cmd_sync_work+0x20b/0x3f0 net/bluetooth/hci_sync.c:332
 process_one_work+0xaaf/0x1480 kernel/workqueue.c:3379
 process_scheduled_works kernel/workqueue.c:3462 [inline]
 worker_thread+0xb05/0x10d0 kernel/workqueue.c:3543
 kthread+0x388/0x470 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
 </TASK>