Freezing user space processes
------------[ cut here ]------------
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.5.25/6015 is trying to acquire lock:
ffffffff8eaf4160 (console_owner){....}-{0:0}, at: console_lock_spinning_enable+0x61/0x80 kernel/printk/printk.c:1902

but task is already holding lock:
ffff88802ad76790 (&p->pi_lock){-.-.}-{2:2}, at: task_call_func+0x8b/0x380 kernel/sched/core.c:4476

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&p->pi_lock){-.-.}-{2:2}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
       _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:166
       class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:571 [inline]
       try_to_wake_up+0xbd/0x1c90 kernel/sched/core.c:4292
       create_worker+0x346/0x750 kernel/workqueue.c:2893
       workqueue_init+0x768/0x930 kernel/workqueue.c:8169
       kernel_init_freeable+0x3d4/0x7b0 init/main.c:1643
       kernel_init+0x1f/0x1e0 init/main.c:1548
       ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
       ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (&pool->lock){-.-.}-{2:2}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __raw_spin_lock include/linux/spinlock_api_smp.h:158 [inline]
       _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:158
       __queue_work+0x5d4/0x12b0 kernel/workqueue.c:2347
       queue_work_on+0x1a9/0x1e0 kernel/workqueue.c:2452
       queue_work include/linux/workqueue.h:699 [inline]
       schedule_work include/linux/workqueue.h:760 [inline]
       hci_uart_tx_wakeup+0x224/0x540 drivers/bluetooth/hci_ldisc.c:138
       hci_uart_tty_wakeup+0x169/0x1b0 drivers/bluetooth/hci_ldisc.c:626
       tty_wakeup+0xe8/0x120 drivers/tty/tty_io.c:515
       tty_port_default_wakeup+0x47/0x60 drivers/tty/tty_port.c:67
       serial8250_tx_chars+0x68f/0x860 drivers/tty/serial/8250/8250_port.c:1723
       serial8250_handle_irq_locked+0x770/0x9a0 drivers/tty/serial/8250/8250_port.c:1837
       serial8250_handle_irq.part.0+0xb4/0x530 drivers/tty/serial/8250/8250_port.c:1853
       serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1849 [inline]
       serial8250_default_handle_irq+0xc2/0x280 drivers/tty/serial/8250/8250_port.c:1867
       serial8250_interrupt+0xf8/0x1b0 drivers/tty/serial/8250/8250_core.c:86
       __handle_irq_event_percpu+0x232/0x880 kernel/irq/handle.c:209
       handle_irq_event_percpu kernel/irq/handle.c:246 [inline]
       handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:263
       handle_edge_irq+0x34c/0x950 kernel/irq/chip.c:859
       generic_handle_irq_desc include/linux/irqdesc.h:188 [inline]
       handle_irq arch/x86/kernel/irq.c:209 [inline]
       call_irq_handler arch/x86/kernel/irq.c:265 [inline]
       __common_interrupt+0xd8/0x2f0 arch/x86/kernel/irq.c:280
       common_interrupt+0xb9/0xe0 arch/x86/kernel/irq.c:273
       asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:665
       __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:188 [inline]
       _raw_spin_unlock_irq+0x29/0x50 kernel/locking/spinlock.c:206
       spin_unlock_irq include/linux/spinlock.h:402 [inline]
       uart_port_unlock_irq include/linux/serial_core.h:779 [inline]
       class_uart_port_lock_irq_destructor include/linux/serial_core.h:796 [inline]
       uart_resume_port+0xcea/0x2000 drivers/tty/serial/serial_core.c:2439
       serial_pnp_resume+0x30/0x40 drivers/tty/serial/8250/8250_pnp.c:512
       pnp_bus_resume+0x1ce/0x2d0 drivers/pnp/driver.c:252
       dpm_run_callback+0x10f/0x210 drivers/base/power/main.c:510
       device_resume+0x49c/0x840 drivers/base/power/main.c:1178
       dpm_resume+0x47d/0x560 drivers/base/power/main.c:1243
       dpm_resume_end+0x13/0x20 drivers/base/power/main.c:1359
       suspend_devices_and_enter+0x441/0x10f0 kernel/power/suspend.c:538
       enter_state kernel/power/suspend.c:618 [inline]
       pm_suspend kernel/power/suspend.c:644 [inline]
       pm_suspend+0x400/0x7b0 kernel/power/suspend.c:636
       state_store+0x101/0x240 kernel/power/main.c:819
       kobj_attr_store+0x58/0x80 lib/kobject.c:840
       sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
       kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x6ac/0x1050 fs/read_write.c:687
       ksys_write+0x12a/0x250 fs/read_write.c:739
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&port_lock_key){-.-.}-{3:3}:
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
       _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:166
       uart_port_lock_irqsave include/linux/serial_core.h:719 [inline]
       serial8250_console_write+0x177/0x1a50 drivers/tty/serial/8250/8250_port.c:3344
       console_emit_next_record kernel/printk/printk.c:3183 [inline]
       console_flush_one_record+0x790/0xe50 kernel/printk/printk.c:3269
       console_flush_all kernel/printk/printk.c:3343 [inline]
       __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
       console_unlock+0x103/0x260 kernel/printk/printk.c:3413
       vprintk_emit+0x407/0x6b0 kernel/printk/printk.c:2479
       _printk+0xcf/0x110 kernel/printk/printk.c:2504
       register_console.cold+0xc0/0x248 kernel/printk/printk.c:4208
       univ8250_console_init+0x6f/0x80 drivers/tty/serial/8250/8250_core.c:515
       console_init+0x3d5/0x5b0 kernel/printk/printk.c:4407
       start_kernel+0x314/0x490 init/main.c:1112
       x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
       x86_64_start_kernel+0x12b/0x130 arch/x86/kernel/head64.c:291
       common_startup_64+0x13e/0x158

-> #0 (console_owner){....}-{0:0}:
       check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
       lock_acquire kernel/locking/lockdep.c:5868 [inline]
       lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
       console_lock_spinning_enable+0x72/0x80 kernel/printk/printk.c:1902
       console_emit_next_record kernel/printk/printk.c:3177 [inline]
       console_flush_one_record+0x739/0xe50 kernel/printk/printk.c:3269
       console_flush_all kernel/printk/printk.c:3343 [inline]
       __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
       console_unlock+0x103/0x260 kernel/printk/printk.c:3413
       vprintk_emit+0x407/0x6b0 kernel/printk/printk.c:2479
       _printk+0xcf/0x110 kernel/printk/printk.c:2504
       __report_bug.cold+0x34/0x141 lib/bug.c:248
       report_bug+0xb2/0x220 lib/bug.c:286
       handle_bug+0x16a/0x2a0 arch/x86/kernel/traps.c:436
       exc_invalid_op+0x17/0x50 arch/x86/kernel/traps.c:490
       asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:593
       __set_task_frozen+0x211/0x2e0 kernel/freezer.c:139
       task_call_func+0x169/0x380 kernel/sched/core.c:4495
       __freeze_task kernel/freezer.c:150 [inline]
       freeze_task+0x151/0x270 kernel/freezer.c:169
       try_to_freeze_tasks+0x243/0x680 kernel/power/process.c:54
       freeze_processes+0xf2/0x1f0 kernel/power/process.c:137
       hibernate.cold+0xf0/0x6a2 kernel/power/hibernate.c:801
       state_store+0x1ff/0x240 kernel/power/main.c:821
       kobj_attr_store+0x58/0x80 lib/kobject.c:840
       sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
       kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x6ac/0x1050 fs/read_write.c:687
       ksys_write+0x12a/0x250 fs/read_write.c:739
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  console_owner --> &pool->lock --> &p->pi_lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&p->pi_lock);
                               lock(&pool->lock);
                               lock(&p->pi_lock);
  lock(console_owner);

 *** DEADLOCK ***

10 locks held by syz.5.25/6015:
 #0: ffff88807c94d7b0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff88802ff5c450 (sb_writers#7){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739
 #2: ffff8880538eb880 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x2c2/0x5f0 fs/kernfs/file.c:336
 #3: ffff8880202a1968 (kn->active#64){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:73 [inline]
 #3: ffff8880202a1968 (kn->active#64){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x332/0x5f0 fs/kernfs/file.c:337
 #4: ffffffff8ea9fc80 (system_transition_mutex){+.+.}-{4:4}, at: lock_system_sleep+0x56/0x70 kernel/power/main.c:71
 #5: ffffffff8e80a098 (tasklist_lock){.+.+}-{3:3}, at: try_to_freeze_tasks+0x148/0x680 kernel/power/process.c:52
 #6: ffffffff8ec181f8 (freezer_lock){....}-{3:3}, at: freeze_task+0x71/0x270 kernel/freezer.c:168
 #7: ffff88802ad76790 (&p->pi_lock){-.-.}-{2:2}, at: task_call_func+0x8b/0x380 kernel/sched/core.c:4476
 #8: ffffffff8ebd45a0 (console_lock){+.+.}-{0:0}, at: _printk+0xcf/0x110 kernel/printk/printk.c:2504
 #9: ffffffff8ebd4618 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:305 [inline]
 #9: ffffffff8ebd4618 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:428 [inline]
 #9: ffffffff8ebd4618 (console_srcu){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:291 [inline]
 #9: ffffffff8ebd4618 (console_srcu){....}-{0:0}, at: console_flush_one_record+0xfd/0xe50 kernel/printk/printk.c:3246

stack backtrace:
CPU: 1 UID: 0 PID: 6015 Comm: syz.5.25 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
 check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
 console_lock_spinning_enable+0x72/0x80 kernel/printk/printk.c:1902
 console_emit_next_record kernel/printk/printk.c:3177 [inline]
 console_flush_one_record+0x739/0xe50 kernel/printk/printk.c:3269
 console_flush_all kernel/printk/printk.c:3343 [inline]
 __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
 console_unlock+0x103/0x260 kernel/printk/printk.c:3413
 vprintk_emit+0x407/0x6b0 kernel/printk/printk.c:2479
 _printk+0xcf/0x110 kernel/printk/printk.c:2504
 __report_bug.cold+0x34/0x141 lib/bug.c:248
 report_bug+0xb2/0x220 lib/bug.c:286
 handle_bug+0x16a/0x2a0 arch/x86/kernel/traps.c:436
 exc_invalid_op+0x17/0x50 arch/x86/kernel/traps.c:490
 asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:593
RIP: 0010:__set_task_frozen+0x211/0x2e0 kernel/freezer.c:139
Code: 0f b6 04 02 84 c0 74 09 3c 03 7f 05 e8 18 9a 85 00 8b ab 98 0b 00 00 31 ff 89 ee e8 29 02 16 00 85 ed 74 09 e8 b0 07 16 00 90 <0f> 0b 90 e8 a7 07 16 00 4c 89 e2 48 b8 00 00 00 00 00 fc ff df 48
RSP: 0018:ffffc90005a37990 EFLAGS: 00010087
RAX: 000000000001e00c RBX: ffff88802ad75d00 RCX: ffffc900049e1000
RDX: 0000000000080000 RSI: ffffffff81f44c10 RDI: ffff888027955d00
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000000 R12: ffff88802ad75d18
R13: 0000000000000002 R14: dffffc0000000000 R15: ffff88802ad76778
 task_call_func+0x169/0x380 kernel/sched/core.c:4495
 __freeze_task kernel/freezer.c:150 [inline]
 freeze_task+0x151/0x270 kernel/freezer.c:169
 try_to_freeze_tasks+0x243/0x680 kernel/power/process.c:54
 freeze_processes+0xf2/0x1f0 kernel/power/process.c:137
 hibernate.cold+0xf0/0x6a2 kernel/power/hibernate.c:801
 state_store+0x1ff/0x240 kernel/power/main.c:821
 kobj_attr_store+0x58/0x80 lib/kobject.c:840
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7faeed19e019
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007faeedfdd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007faeed425fa0 RCX: 00007faeed19e019
RDX: 0000000000000005 RSI: 00002000000001c0 RDI: 0000000000000005
RBP: 00007faeed23500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007faeed426038 R14: 00007faeed425fa0 R15: 00007ffc6ba11058
 </TASK>
debug_locks && p->lockdep_depth
WARNING: kernel/freezer.c:139 at __set_task_frozen+0x211/0x2e0 kernel/freezer.c:139, CPU#1: syz.5.25/6015
Modules linked in:
CPU: 1 UID: 0 PID: 6015 Comm: syz.5.25 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:__set_task_frozen+0x211/0x2e0 kernel/freezer.c:139
Code: 0f b6 04 02 84 c0 74 09 3c 03 7f 05 e8 18 9a 85 00 8b ab 98 0b 00 00 31 ff 89 ee e8 29 02 16 00 85 ed 74 09 e8 b0 07 16 00 90 <0f> 0b 90 e8 a7 07 16 00 4c 89 e2 48 b8 00 00 00 00 00 fc ff df 48
RSP: 0018:ffffc90005a37990 EFLAGS: 00010087
RAX: 000000000001e00c RBX: ffff88802ad75d00 RCX: ffffc900049e1000
RDX: 0000000000080000 RSI: ffffffff81f44c10 RDI: ffff888027955d00
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000000 R12: ffff88802ad75d18
R13: 0000000000000002 R14: dffffc0000000000 R15: ffff88802ad76778
FS:  00007faeedfdd6c0(0000) GS:ffff888123ed9000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0f219eb700 CR3: 0000000023add000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 task_call_func+0x169/0x380 kernel/sched/core.c:4495
 __freeze_task kernel/freezer.c:150 [inline]
 freeze_task+0x151/0x270 kernel/freezer.c:169
 try_to_freeze_tasks+0x243/0x680 kernel/power/process.c:54
 freeze_processes+0xf2/0x1f0 kernel/power/process.c:137
 hibernate.cold+0xf0/0x6a2 kernel/power/hibernate.c:801
 state_store+0x1ff/0x240 kernel/power/main.c:821
 kobj_attr_store+0x58/0x80 lib/kobject.c:840
 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145
 kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6ac/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7faeed19e019
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007faeedfdd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007faeed425fa0 RCX: 00007faeed19e019
RDX: 0000000000000005 RSI: 00002000000001c0 RDI: 0000000000000005
RBP: 00007faeed23500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007faeed426038 R14: 00007faeed425fa0 R15: 00007ffc6ba11058
 </TASK>