Freezing user space processes
------------[ cut here ]------------
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.4.2382/16363 is trying to acquire lock:
ffffffff8eb4bf40 (console_owner){..-.}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:305 [inline]
ffffffff8eb4bf40 (console_owner){..-.}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:428 [inline]
ffffffff8eb4bf40 (console_owner){..-.}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:291 [inline]
ffffffff8eb4bf40 (console_owner){..-.}-{0:0}, at: console_flush_one_record kernel/printk/printk.c:3246 [inline]
ffffffff8eb4bf40 (console_owner){..-.}-{0:0}, at: console_flush_all+0x123/0xaf0 kernel/printk/printk.c:3343

but task is already holding lock:
ffff88803177c890 (&p->pi_lock){-.-.}-{2:2}, at: task_call_func+0x42/0x260 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}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
       _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:166
       class_raw_spinlock_irqsave_constructor include/linux/spinlock.h:572 [inline]
       try_to_wake_up+0x67/0x14d0 kernel/sched/core.c:4292
       autoremove_wake_function+0x17/0x100 kernel/sched/wait.c:403
       __wake_up_common kernel/sched/wait.c:108 [inline]
       __wake_up_common_lock+0x13a/0x1f0 kernel/sched/wait.c:125
       tty_port_default_wakeup+0xc8/0x100 drivers/tty/tty_port.c:67
       serial8250_tx_chars+0x70e/0x950 drivers/tty/serial/8250/8250_port.c:1723
       serial8250_handle_irq+0x166/0x550 drivers/tty/serial/8250/8250_port.c:1853
       serial8250_default_handle_irq+0xbf/0x1e0 drivers/tty/serial/8250/8250_port.c:1867
       serial8250_interrupt+0x8d/0x160 drivers/tty/serial/8250/8250_core.c:86
       __handle_irq_event_percpu+0x216/0x9a0 kernel/irq/handle.c:209
       handle_irq_event_percpu kernel/irq/handle.c:246 [inline]
       handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:263
       handle_edge_irq+0x1f4/0x8a0 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:-1 [inline]
       __common_interrupt+0x141/0x1f0 arch/x86/kernel/irq.c:280
       common_interrupt+0xb6/0xe0 arch/x86/kernel/irq.c:273
       asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:665
       ____sys_recvmsg+0x1e6/0x4a0 net/socket.c:2904
       ___sys_recvmsg+0x213/0x5a0 net/socket.c:2946
       do_recvmmsg+0x31a/0x7f0 net/socket.c:3041
       __sys_recvmmsg net/socket.c:3115 [inline]
       __do_sys_recvmmsg net/socket.c:3138 [inline]
       __se_sys_recvmmsg net/socket.c:3131 [inline]
       __x64_sys_recvmmsg+0x198/0x250 net/socket.c:3131
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&tty->write_wait){-...}-{3:3}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
       _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:166
       __wake_up_common_lock+0x30/0x1f0 kernel/sched/wait.c:124
       tty_port_default_wakeup+0xc8/0x100 drivers/tty/tty_port.c:67
       serial8250_tx_chars+0x70e/0x950 drivers/tty/serial/8250/8250_port.c:1723
       serial8250_handle_irq+0x166/0x550 drivers/tty/serial/8250/8250_port.c:1853
       serial8250_default_handle_irq+0xbf/0x1e0 drivers/tty/serial/8250/8250_port.c:1867
       serial8250_interrupt+0x8d/0x160 drivers/tty/serial/8250/8250_core.c:86
       __handle_irq_event_percpu+0x216/0x9a0 kernel/irq/handle.c:209
       handle_irq_event_percpu kernel/irq/handle.c:246 [inline]
       handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:263
       handle_edge_irq+0x1f4/0x8a0 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:-1 [inline]
       __common_interrupt+0x141/0x1f0 arch/x86/kernel/irq.c:280
       common_interrupt+0xb6/0xe0 arch/x86/kernel/irq.c:273
       asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:665
       __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline]
       _raw_spin_unlock_irqrestore+0x47/0x80 kernel/locking/spinlock.c:198
       spin_unlock_irqrestore include/linux/spinlock.h:408 [inline]
       uart_port_unlock_irqrestore include/linux/serial_core.h:790 [inline]
       uart_port_unlock_deref drivers/tty/serial/serial_core.c:91 [inline]
       uart_write+0x3c0/0x9f0 drivers/tty/serial/serial_core.c:630
       process_output_block drivers/tty/n_tty.c:557 [inline]
       n_tty_write+0xd49/0x11e0 drivers/tty/n_tty.c:2366
       iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
       file_tty_write+0x509/0x9c0 drivers/tty/tty_io.c:1081
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x612/0xba0 fs/read_write.c:687
       ksys_write+0x150/0x270 fs/read_write.c:739
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&port_lock_key){-.-.}-{3:3}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
       _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:166
       uart_port_lock_irqsave include/linux/serial_core.h:719 [inline]
       serial8250_console_write+0x153/0x1ba0 drivers/tty/serial/8250/8250_port.c:3344
       console_emit_next_record kernel/printk/printk.c:3183 [inline]
       console_flush_one_record kernel/printk/printk.c:3269 [inline]
       console_flush_all+0x6ea/0xaf0 kernel/printk/printk.c:3343
       __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
       console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413
       vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479
       _printk+0xdd/0x130 kernel/printk/printk.c:2504
       register_console+0xbc3/0xfc0 kernel/printk/printk.c:4208
       univ8250_console_init+0x3a/0x70 drivers/tty/serial/8250/8250_core.c:515
       console_init+0x10b/0x4a0 kernel/printk/printk.c:4407
       start_kernel+0x238/0x3e0 init/main.c:1112
       x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
       x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291
       common_startup_64+0x13e/0x157

-> #0 (console_owner){..-.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:3165 [inline]
       check_prevs_add kernel/locking/lockdep.c:3284 [inline]
       validate_chain kernel/locking/lockdep.c:3908 [inline]
       __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
       lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
       console_lock_spinning_enable kernel/printk/printk.c:1902 [inline]
       console_emit_next_record kernel/printk/printk.c:3177 [inline]
       console_flush_one_record kernel/printk/printk.c:3269 [inline]
       console_flush_all+0x693/0xaf0 kernel/printk/printk.c:3343
       __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
       console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413
       vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479
       _printk+0xdd/0x130 kernel/printk/printk.c:2504
       __report_bug+0x349/0x570 lib/bug.c:248
       report_bug+0x16a/0x220 lib/bug.c:286
       handle_bug+0x9c/0x200 arch/x86/kernel/traps.c:436
       exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:490
       asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:593
       __set_task_frozen+0x260/0x340 kernel/freezer.c:139
       task_call_func+0x1aa/0x260 kernel/sched/core.c:4495
       __freeze_task kernel/freezer.c:150 [inline]
       freeze_task+0x229/0x3b0 kernel/freezer.c:169
       try_to_freeze_tasks+0x190/0x620 kernel/power/process.c:54
       freeze_processes+0xce/0x1e0 kernel/power/process.c:137
       suspend_freeze_processes kernel/power/power.h:281 [inline]
       suspend_prepare kernel/power/suspend.c:387 [inline]
       enter_state kernel/power/suspend.c:609 [inline]
       pm_suspend+0x2f1/0x760 kernel/power/suspend.c:644
       state_store+0x206/0x290 kernel/power/main.c:819
       kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
       new_sync_write fs/read_write.c:595 [inline]
       vfs_write+0x612/0xba0 fs/read_write.c:687
       ksys_write+0x150/0x270 fs/read_write.c:739
       do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
       do_syscall_64+0x174/0x580 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 --> &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 ***

10 locks held by syz.4.2382/16363:
 #0: ffff888077adbcf0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320 fs/file.c:1259
 #1: ffff88802c4cc450 (sb_writers#7){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2733 [inline]
 #1: ffff88802c4cc450 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0 fs/read_write.c:683
 #2: ffff888051d80080 (&of->mutex){+.+.}-{4:4}, at: kernfs_fop_write_iter+0x1d8/0x540 fs/kernfs/file.c:336
 #3: ffff88801f28e968 (kn->active#92){.+.+}-{0:0}, at: kernfs_get_active_of fs/kernfs/file.c:73 [inline]
 #3: ffff88801f28e968 (kn->active#92){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x22b/0x540 fs/kernfs/file.c:337
 #4: ffffffff8ea02160 (system_transition_mutex){+.+.}-{4:4}, at: enter_state kernel/power/suspend.c:591 [inline]
 #4: ffffffff8ea02160 (system_transition_mutex){+.+.}-{4:4}, at: pm_suspend+0x3c7/0x760 kernel/power/suspend.c:644
 #5: ffffffff8e80a058 (tasklist_lock){.+.+}-{3:3}, at: try_to_freeze_tasks+0xe5/0x620 kernel/power/process.c:52
 #6: ffffffff8eb7b7b8 (freezer_lock){....}-{3:3}, at: freeze_task+0x7e/0x3b0 kernel/freezer.c:168
 #7: ffff88803177c890 (&p->pi_lock){-.-.}-{2:2}, at: task_call_func+0x42/0x260 kernel/sched/core.c:4476
 #8: ffffffff8eb4bfa0 (console_lock){+.+.}-{0:0}, at: _printk+0xdd/0x130 kernel/printk/printk.c:2504
 #9: ffffffff8ea33838 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:305 [inline]
 #9: ffffffff8ea33838 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:428 [inline]
 #9: ffffffff8ea33838 (console_srcu){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:291 [inline]
 #9: ffffffff8ea33838 (console_srcu){....}-{0:0}, at: console_flush_one_record kernel/printk/printk.c:3246 [inline]
 #9: ffffffff8ea33838 (console_srcu){....}-{0:0}, at: console_flush_all+0x123/0xaf0 kernel/printk/printk.c:3343

stack backtrace:
CPU: 0 UID: 0 PID: 16363 Comm: syz.4.2382 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
 check_prev_add kernel/locking/lockdep.c:3165 [inline]
 check_prevs_add kernel/locking/lockdep.c:3284 [inline]
 validate_chain kernel/locking/lockdep.c:3908 [inline]
 __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
 console_lock_spinning_enable kernel/printk/printk.c:1902 [inline]
 console_emit_next_record kernel/printk/printk.c:3177 [inline]
 console_flush_one_record kernel/printk/printk.c:3269 [inline]
 console_flush_all+0x693/0xaf0 kernel/printk/printk.c:3343
 __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
 console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413
 vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479
 _printk+0xdd/0x130 kernel/printk/printk.c:2504
 __report_bug+0x349/0x570 lib/bug.c:248
 report_bug+0x16a/0x220 lib/bug.c:286
 handle_bug+0x9c/0x200 arch/x86/kernel/traps.c:436
 exc_invalid_op+0x1a/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+0x260/0x340 kernel/freezer.c:139
Code: 00 80 00 00 89 e8 5b 41 5c 41 5d 41 5e 41 5f 5d e9 20 43 5e ff cc e8 9f 14 15 00 90 0f 0b 90 e9 f7 fe ff ff e8 91 14 15 00 90 <0f> 0b 90 eb 93 44 89 e1 80 e1 07 80 c1 03 38 c1 0f 8c c3 fd ff ff
RSP: 0018:ffffc900052d79f0 EFLAGS: 00010083
RAX: ffffffff81b1fdff RBX: ffff88803177be00 RCX: 0000000000080000
RDX: ffffc90005f69000 RSI: 00000000000518cc RDI: 00000000000518cd
RBP: 0000000000000003 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: ffffffff81b1fba0 R12: ffff88803177be18
R13: 1ffff110062ef7c3 R14: 0000000000000000 R15: ffff88803177c998
 task_call_func+0x1aa/0x260 kernel/sched/core.c:4495
 __freeze_task kernel/freezer.c:150 [inline]
 freeze_task+0x229/0x3b0 kernel/freezer.c:169
 try_to_freeze_tasks+0x190/0x620 kernel/power/process.c:54
 freeze_processes+0xce/0x1e0 kernel/power/process.c:137
 suspend_freeze_processes kernel/power/power.h:281 [inline]
 suspend_prepare kernel/power/suspend.c:387 [inline]
 enter_state kernel/power/suspend.c:609 [inline]
 pm_suspend+0x2f1/0x760 kernel/power/suspend.c:644
 state_store+0x206/0x290 kernel/power/main.c:819
 kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:687
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fecb819e019
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:00007fecb8f9c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fecb8425fa0 RCX: 00007fecb819e019
RDX: 0000000000000004 RSI: 0000200000000200 RDI: 0000000000000005
RBP: 00007fecb823500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fecb8426038 R14: 00007fecb8425fa0 R15: 00007ffdee22dc58
 </TASK>
debug_locks && p->lockdep_depth
WARNING: kernel/freezer.c:139 at __set_task_frozen+0x260/0x340 kernel/freezer.c:139, CPU#0: syz.4.2382/16363
Modules linked in:
CPU: 0 UID: 0 PID: 16363 Comm: syz.4.2382 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
RIP: 0010:__set_task_frozen+0x260/0x340 kernel/freezer.c:139
Code: 00 80 00 00 89 e8 5b 41 5c 41 5d 41 5e 41 5f 5d e9 20 43 5e ff cc e8 9f 14 15 00 90 0f 0b 90 e9 f7 fe ff ff e8 91 14 15 00 90 <0f> 0b 90 eb 93 44 89 e1 80 e1 07 80 c1 03 38 c1 0f 8c c3 fd ff ff
RSP: 0018:ffffc900052d79f0 EFLAGS: 00010083
RAX: ffffffff81b1fdff RBX: ffff88803177be00 RCX: 0000000000080000
RDX: ffffc90005f69000 RSI: 00000000000518cc RDI: 00000000000518cd
RBP: 0000000000000003 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: ffffffff81b1fba0 R12: ffff88803177be18
R13: 1ffff110062ef7c3 R14: 0000000000000000 R15: ffff88803177c998
FS:  00007fecb8f9c6c0(0000) GS:ffff888124f4b000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe9dd755000 CR3: 00000000564b3000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 task_call_func+0x1aa/0x260 kernel/sched/core.c:4495
 __freeze_task kernel/freezer.c:150 [inline]
 freeze_task+0x229/0x3b0 kernel/freezer.c:169
 try_to_freeze_tasks+0x190/0x620 kernel/power/process.c:54
 freeze_processes+0xce/0x1e0 kernel/power/process.c:137
 suspend_freeze_processes kernel/power/power.h:281 [inline]
 suspend_prepare kernel/power/suspend.c:387 [inline]
 enter_state kernel/power/suspend.c:609 [inline]
 pm_suspend+0x2f1/0x760 kernel/power/suspend.c:644
 state_store+0x206/0x290 kernel/power/main.c:819
 kernfs_fop_write_iter+0x3a4/0x540 fs/kernfs/file.c:345
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:687
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fecb819e019
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:00007fecb8f9c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fecb8425fa0 RCX: 00007fecb819e019
RDX: 0000000000000004 RSI: 0000200000000200 RDI: 0000000000000005
RBP: 00007fecb823500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fecb8426038 R14: 00007fecb8425fa0 R15: 00007ffdee22dc58
 </TASK>