Freezing user space processes
------------[ cut here ]------------
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.116/6359 is trying to acquire lock:
ffffffff8d1260a0 (console_owner){....}-{0:0}, at: console_trylock_spinning kernel/printk/printk.c:1995 [inline]
ffffffff8d1260a0 (console_owner){....}-{0:0}, at: vprintk_emit+0x30b/0x610 kernel/printk/printk.c:2340

but task is already holding lock:
ffff8880240ca818 (&p->pi_lock){-.-.}-{2:2}, at: task_call_func+0x43/0x260 kernel/sched/core.c:4412

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&p->pi_lock){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xb4/0x100 kernel/locking/spinlock.c:162
       class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:523 [inline]
       try_to_wake_up+0x5b/0x10e0 kernel/sched/core.c:4233
       __wake_up_common+0x28e/0x4d0 kernel/sched/wait.c:107
       __wake_up_common_lock kernel/sched/wait.c:138 [inline]
       __wake_up+0x125/0x1a0 kernel/sched/wait.c:160
       tty_port_default_wakeup+0xa2/0xf0 drivers/tty/tty_port.c:69
       serial8250_tx_chars+0x6a2/0x8b0 drivers/tty/serial/8250/8250_port.c:1837
       serial8250_handle_irq+0x567/0x730 drivers/tty/serial/8250/8250_port.c:1944
       serial8250_default_handle_irq+0xb8/0x1a0 drivers/tty/serial/8250/8250_port.c:1964
       serial8250_interrupt+0x9f/0x1c0 drivers/tty/serial/8250/8250_core.c:127
       __handle_irq_event_percpu+0x271/0x940 kernel/irq/handle.c:158
       handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
       handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:210
       handle_edge_irq+0x246/0xb20 kernel/irq/chip.c:831
       generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
       handle_irq arch/x86/kernel/irq.c:240 [inline]
       __common_interrupt+0x13b/0x230 arch/x86/kernel/irq.c:259
       common_interrupt+0xb4/0xd0 arch/x86/kernel/irq.c:249
       asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:678
       native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
       pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:147
       arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
       default_idle+0x13/0x20 arch/x86/kernel/process.c:753
       default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
       cpuidle_idle_call kernel/sched/idle.c:178 [inline]
       do_idle+0x334/0x5c0 kernel/sched/idle.c:302
       cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:401
       start_secondary+0xee/0xf0 arch/x86/kernel/smpboot.c:323
       secondary_startup_64_no_verify+0x179/0x17b

-> #2 (&tty->write_wait){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xb4/0x100 kernel/locking/spinlock.c:162
       __wake_up_common_lock kernel/sched/wait.c:137 [inline]
       __wake_up+0x10b/0x1a0 kernel/sched/wait.c:160
       tty_port_default_wakeup+0xa2/0xf0 drivers/tty/tty_port.c:69
       serial8250_tx_chars+0x6a2/0x8b0 drivers/tty/serial/8250/8250_port.c:1837
       serial8250_handle_irq+0x567/0x730 drivers/tty/serial/8250/8250_port.c:1944
       serial8250_default_handle_irq+0xb8/0x1a0 drivers/tty/serial/8250/8250_port.c:1964
       serial8250_interrupt+0x9f/0x1c0 drivers/tty/serial/8250/8250_core.c:127
       __handle_irq_event_percpu+0x271/0x940 kernel/irq/handle.c:158
       handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
       handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:210
       handle_edge_irq+0x246/0xb20 kernel/irq/chip.c:831
       generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
       handle_irq arch/x86/kernel/irq.c:240 [inline]
       __common_interrupt+0x13b/0x230 arch/x86/kernel/irq.c:259
       common_interrupt+0xb4/0xd0 arch/x86/kernel/irq.c:249
       asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:678
       __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
       _raw_spin_unlock_irqrestore+0xc0/0x120 kernel/locking/spinlock.c:194
       spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
       uart_write+0x45b/0x5d0 drivers/tty/serial/serial_core.c:634
       process_output_block drivers/tty/n_tty.c:580 [inline]
       n_tty_write+0xd3d/0x11e0 drivers/tty/n_tty.c:2395
       iterate_tty_write drivers/tty/tty_io.c:1017 [inline]
       file_tty_write+0x529/0x960 drivers/tty/tty_io.c:1088
       call_write_iter include/linux/fs.h:2018 [inline]
       new_sync_write fs/read_write.c:491 [inline]
       vfs_write+0x474/0x9a0 fs/read_write.c:584
       ksys_write+0x151/0x260 fs/read_write.c:637
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&port_lock_key){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xb4/0x100 kernel/locking/spinlock.c:162
       serial8250_console_write+0x181/0x18b0 drivers/tty/serial/8250/8250_port.c:3439
       console_emit_next_record kernel/printk/printk.c:2944 [inline]
       console_flush_all+0x6ad/0xcf0 kernel/printk/printk.c:3000
       console_unlock+0xad/0x350 kernel/printk/printk.c:3069
       vprintk_emit+0x497/0x610 kernel/printk/printk.c:2341
       _printk+0xde/0x130 kernel/printk/printk.c:2366
       register_console+0xb96/0xf00 kernel/printk/printk.c:3583
       univ8250_console_init+0x45/0x50 drivers/tty/serial/8250/8250_core.c:717
       console_init+0x17b/0x5d0 kernel/printk/printk.c:3726
       start_kernel+0x2c8/0x4e0 init/main.c:982
       x86_64_start_reservations+0x2a/0x30 arch/x86/kernel/head64.c:555
       copy_bootdata+0x0/0xd0 arch/x86/kernel/head64.c:536
       secondary_startup_64_no_verify+0x179/0x17b

-> #0 (console_owner){....}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
       lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
       console_trylock_spinning kernel/printk/printk.c:1995 [inline]
       vprintk_emit+0x328/0x610 kernel/printk/printk.c:2340
       _printk+0xde/0x130 kernel/printk/printk.c:2366
       __report_bug lib/bug.c:195 [inline]
       report_bug+0x34e/0x4f0 lib/bug.c:219
       handle_bug+0xcf/0x120 arch/x86/kernel/traps.c:310
       exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:345
       asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:606
       __set_task_frozen+0x210/0x2d0 kernel/freezer.c:133
       task_call_func+0x1a2/0x260 kernel/sched/core.c:4427
       __freeze_task kernel/freezer.c:144 [inline]
       freeze_task+0x217/0x3a0 kernel/freezer.c:163
       try_to_freeze_tasks+0x190/0x620 kernel/power/process.c:54
       freeze_processes+0xc9/0x1e0 kernel/power/process.c:137
       hibernate+0x121/0x400 kernel/power/hibernate.c:754
       state_store+0x22f/0x290 kernel/power/main.c:710
       kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
       call_write_iter include/linux/fs.h:2018 [inline]
       new_sync_write fs/read_write.c:491 [inline]
       vfs_write+0x474/0x9a0 fs/read_write.c:584
       ksys_write+0x151/0x260 fs/read_write.c:637
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
  console_owner --> &tty->write_wait --> &p->pi_lock

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

8 locks held by syz.2.116/6359:
 #0: ffff8880304c40c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff88802c4cc418 (sb_writers#8){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
 #2: ffff8880778f0488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1dc/0x520 fs/kernfs/file.c:343
 #3: ffff88801d2569b8 (kn->active#64){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:80 [inline]
 #3: ffff88801d2569b8 (kn->active#64){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x236/0x520 fs/kernfs/file.c:344
 #4: ffffffff8cfe58a8 (system_transition_mutex){+.+.}-{3:3}, at: lock_system_sleep+0x49/0x70 kernel/power/main.c:56
 #5: ffffffff8ce0a058 (tasklist_lock){.+.+}-{2:2}, at: try_to_freeze_tasks+0xe5/0x620 kernel/power/process.c:52
 #6: ffffffff8d144ef8 (freezer_lock){....}-{2:2}, at: freeze_task+0x80/0x3a0 kernel/freezer.c:162
 #7: ffff8880240ca818 (&p->pi_lock){-.-.}-{2:2}, at: task_call_func+0x43/0x260 kernel/sched/core.c:4412

stack backtrace:
CPU: 0 PID: 6359 Comm: syz.2.116 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 console_trylock_spinning kernel/printk/printk.c:1995 [inline]
 vprintk_emit+0x328/0x610 kernel/printk/printk.c:2340
 _printk+0xde/0x130 kernel/printk/printk.c:2366
 __report_bug lib/bug.c:195 [inline]
 report_bug+0x34e/0x4f0 lib/bug.c:219
 handle_bug+0xcf/0x120 arch/x86/kernel/traps.c:310
 exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:345
 asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:606
RIP: 0010:__set_task_frozen+0x210/0x2d0 kernel/freezer.c:133
Code: 41 c7 06 00 80 00 00 bd 00 80 00 00 89 e8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 4c 8f 11 00 0f 0b e9 0a ff ff ff e8 40 8f 11 00 <0f> 0b eb 9d 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c 14 fe ff ff 4c
RSP: 0018:ffffc90006167a70 EFLAGS: 00010046
RAX: ffffffff8175e240 RBX: ffff8880240c9e00 RCX: 0000000000080000
RDX: ffffc9000ddbc000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: 0000000000000003 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000c2cf30 R12: 0000000000000000
R13: 1ffff110048193c3 R14: ffff8880240c9e18 R15: ffff8880240ca8d8
 task_call_func+0x1a2/0x260 kernel/sched/core.c:4427
 __freeze_task kernel/freezer.c:144 [inline]
 freeze_task+0x217/0x3a0 kernel/freezer.c:163
 try_to_freeze_tasks+0x190/0x620 kernel/power/process.c:54
 freeze_processes+0xc9/0x1e0 kernel/power/process.c:137
 hibernate+0x121/0x400 kernel/power/hibernate.c:754
 state_store+0x22f/0x290 kernel/power/main.c:710
 kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2018 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x474/0x9a0 fs/read_write.c:584
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fc87739e019
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:00007fc8782cd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc877625fa0 RCX: 00007fc87739e019
RDX: 0000000000000004 RSI: 0000200000000100 RDI: 0000000000000003
RBP: 00007fc87743500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc877626038 R14: 00007fc877625fa0 R15: 00007ffebee55778
 </TASK>
WARNING: CPU: 0 PID: 6359 at kernel/freezer.c:133 __set_task_frozen+0x210/0x2d0 kernel/freezer.c:133
Modules linked in:
CPU: 0 PID: 6359 Comm: syz.2.116 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:__set_task_frozen+0x210/0x2d0 kernel/freezer.c:133
Code: 41 c7 06 00 80 00 00 bd 00 80 00 00 89 e8 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 4c 8f 11 00 0f 0b e9 0a ff ff ff e8 40 8f 11 00 <0f> 0b eb 9d 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c 14 fe ff ff 4c
RSP: 0018:ffffc90006167a70 EFLAGS: 00010046
RAX: ffffffff8175e240 RBX: ffff8880240c9e00 RCX: 0000000000080000
RDX: ffffc9000ddbc000 RSI: 000000000007ffff RDI: 0000000000080000
RBP: 0000000000000003 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000c2cf30 R12: 0000000000000000
R13: 1ffff110048193c3 R14: ffff8880240c9e18 R15: ffff8880240ca8d8
FS:  00007fc8782cd6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fcb8f3556c8 CR3: 0000000056034000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 task_call_func+0x1a2/0x260 kernel/sched/core.c:4427
 __freeze_task kernel/freezer.c:144 [inline]
 freeze_task+0x217/0x3a0 kernel/freezer.c:163
 try_to_freeze_tasks+0x190/0x620 kernel/power/process.c:54
 freeze_processes+0xc9/0x1e0 kernel/power/process.c:137
 hibernate+0x121/0x400 kernel/power/hibernate.c:754
 state_store+0x22f/0x290 kernel/power/main.c:710
 kernfs_fop_write_iter+0x3a4/0x520 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2018 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x474/0x9a0 fs/read_write.c:584
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fc87739e019
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:00007fc8782cd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc877625fa0 RCX: 00007fc87739e019
RDX: 0000000000000004 RSI: 0000200000000100 RDI: 0000000000000003
RBP: 00007fc87743500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc877626038 R14: 00007fc877625fa0 R15: 00007ffebee55778
 </TASK>