ttyS ttyS3: tty_port_close_start: tty->count = 1 port count = 2 ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.7.2403/16381 is trying to acquire lock: ffffffff8e2d19a0 (console_owner){-.-.}-{0:0}, at: console_lock_spinning_enable+0x61/0x80 kernel/printk/printk.c:1897 but task is already holding lock: ffff8880256d8d40 (&port->lock#2){-.-.}-{3:3}, at: class_spinlock_irqsave_constructor include/linux/spinlock.h:585 [inline] ffff8880256d8d40 (&port->lock#2){-.-.}-{3:3}, at: tty_port_close_start+0x69/0x5a0 drivers/tty/tty_port.c:599 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&port->lock#2){-.-.}-{3:3}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162 class_spinlock_irqsave_constructor include/linux/spinlock.h:585 [inline] tty_port_tty_get+0x21/0x120 drivers/tty/tty_port.c:301 class_tty_port_tty_constructor include/linux/tty_port.h:280 [inline] tty_port_default_wakeup+0x15/0x60 drivers/tty/tty_port.c:66 serial8250_tx_chars+0x68e/0x860 drivers/tty/serial/8250/8250_port.c:1719 serial8250_handle_irq+0x761/0xcb0 drivers/tty/serial/8250/8250_port.c:1827 serial8250_default_handle_irq+0x9e/0x270 drivers/tty/serial/8250/8250_port.c:1846 serial8250_interrupt+0xf8/0x1d0 drivers/tty/serial/8250/8250_core.c:82 __handle_irq_event_percpu+0x236/0x920 kernel/irq/handle.c:203 handle_irq_event_percpu kernel/irq/handle.c:240 [inline] handle_irq_event+0xab/0x1e0 kernel/irq/handle.c:257 handle_edge_irq+0x3ca/0x9e0 kernel/irq/chip.c:855 generic_handle_irq_desc include/linux/irqdesc.h:173 [inline] handle_irq arch/x86/kernel/irq.c:254 [inline] call_irq_handler arch/x86/kernel/irq.c:310 [inline] __common_interrupt+0xd0/0x2f0 arch/x86/kernel/irq.c:325 common_interrupt+0xba/0xe0 arch/x86/kernel/irq.c:318 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:688 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline] _raw_spin_unlock_irqrestore+0x31/0x80 kernel/locking/spinlock.c:194 spin_unlock_irqrestore include/linux/spinlock.h:406 [inline] uart_port_unlock_irqrestore include/linux/serial_core.h:788 [inline] uart_port_unlock_deref drivers/tty/serial/serial_core.c:91 [inline] uart_port_unlock_deref drivers/tty/serial/serial_core.c:88 [inline] uart_write+0x2a4/0xb30 drivers/tty/serial/serial_core.c:634 process_output_block drivers/tty/n_tty.c:561 [inline] n_tty_write+0x41e/0x11e0 drivers/tty/n_tty.c:2377 iterate_tty_write drivers/tty/tty_io.c:1006 [inline] file_tty_write.constprop.0+0x503/0x9b0 drivers/tty/tty_io.c:1081 tty_write drivers/tty/tty_io.c:1102 [inline] redirected_tty_write drivers/tty/tty_io.c:1125 [inline] redirected_tty_write+0xd4/0x150 drivers/tty/tty_io.c:1105 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x7d3/0x11d0 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 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:110 [inline] _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:162 uart_port_lock_irqsave include/linux/serial_core.h:717 [inline] serial8250_console_write+0x181/0x1890 drivers/tty/serial/8250/8250_port.c:3301 console_emit_next_record kernel/printk/printk.c:3111 [inline] console_flush_all+0x801/0xc60 kernel/printk/printk.c:3199 __console_flush_and_unlock kernel/printk/printk.c:3258 [inline] console_unlock+0xd8/0x210 kernel/printk/printk.c:3298 vprintk_emit+0x3d7/0x680 kernel/printk/printk.c:2423 _printk+0xc7/0x100 kernel/printk/printk.c:2448 register_console+0xc2d/0x11b0 kernel/printk/printk.c:4099 univ8250_console_init+0x5f/0x90 drivers/tty/serial/8250/8250_core.c:511 console_init+0x152/0x680 kernel/printk/printk.c:4298 start_kernel+0x29f/0x4e0 init/main.c:1048 x86_64_start_reservations+0x18/0x30 arch/x86/kernel/head64.c:310 x86_64_start_kernel+0x130/0x190 arch/x86/kernel/head64.c:291 common_startup_64+0x13e/0x148 -> #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+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 console_lock_spinning_enable+0x72/0x80 kernel/printk/printk.c:1897 console_emit_next_record kernel/printk/printk.c:3105 [inline] console_flush_all+0x7aa/0xc60 kernel/printk/printk.c:3199 __console_flush_and_unlock kernel/printk/printk.c:3258 [inline] console_unlock+0xd8/0x210 kernel/printk/printk.c:3298 vprintk_emit+0x3d7/0x680 kernel/printk/printk.c:2423 _printk+0xc7/0x100 kernel/printk/printk.c:2448 tty_port_close_start+0x1e8/0x5a0 drivers/tty/tty_port.c:601 tty_port_close+0x26/0x190 drivers/tty/tty_port.c:682 uart_close+0x7b/0x220 drivers/tty/serial/serial_core.c:1740 tty_release+0x3af/0x1430 drivers/tty/tty_io.c:1745 __fput+0x402/0xb70 fs/file_table.c:468 task_work_run+0x150/0x240 kernel/task_work.c:227 exit_task_work include/linux/task_work.h:40 [inline] do_exit+0x86f/0x2bf0 kernel/exit.c:966 do_group_exit+0xd3/0x2a0 kernel/exit.c:1107 __do_sys_exit_group kernel/exit.c:1118 [inline] __se_sys_exit_group kernel/exit.c:1116 [inline] __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1116 x64_sys_call+0x150b/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 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 --> &port_lock_key --> &port->lock#2 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&port->lock#2); lock(&port_lock_key); lock(&port->lock#2); lock(console_owner); *** DEADLOCK *** 4 locks held by syz.7.2403/16381: #0: ffff8880601d91c0 (&tty->legacy_mutex){+.+.}-{4:4}, at: tty_release+0x86/0x1430 drivers/tty/tty_io.c:1727 #1: ffff8880256d8d40 (&port->lock#2){-.-.}-{3:3}, at: class_spinlock_irqsave_constructor include/linux/spinlock.h:585 [inline] #1: ffff8880256d8d40 (&port->lock#2){-.-.}-{3:3}, at: tty_port_close_start+0x69/0x5a0 drivers/tty/tty_port.c:599 #2: ffffffff8e3b1de0 (console_lock){+.+.}-{0:0}, at: _printk+0xc7/0x100 kernel/printk/printk.c:2448 #3: ffffffff8e3b1e50 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:336 [inline] #3: ffffffff8e3b1e50 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:335 [inline] #3: ffffffff8e3b1e50 (console_srcu){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:289 [inline] #3: ffffffff8e3b1e50 (console_srcu){....}-{0:0}, at: console_flush_all+0x158/0xc60 kernel/printk/printk.c:3176 stack backtrace: CPU: 1 UID: 0 PID: 16381 Comm: syz.7.2403 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2043 check_noncircular+0x14c/0x170 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+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 console_lock_spinning_enable+0x72/0x80 kernel/printk/printk.c:1897 console_emit_next_record kernel/printk/printk.c:3105 [inline] console_flush_all+0x7aa/0xc60 kernel/printk/printk.c:3199 __console_flush_and_unlock kernel/printk/printk.c:3258 [inline] console_unlock+0xd8/0x210 kernel/printk/printk.c:3298 vprintk_emit+0x3d7/0x680 kernel/printk/printk.c:2423 _printk+0xc7/0x100 kernel/printk/printk.c:2448 tty_port_close_start+0x1e8/0x5a0 drivers/tty/tty_port.c:601 tty_port_close+0x26/0x190 drivers/tty/tty_port.c:682 uart_close+0x7b/0x220 drivers/tty/serial/serial_core.c:1740 tty_release+0x3af/0x1430 drivers/tty/tty_io.c:1745 __fput+0x402/0xb70 fs/file_table.c:468 task_work_run+0x150/0x240 kernel/task_work.c:227 exit_task_work include/linux/task_work.h:40 [inline] do_exit+0x86f/0x2bf0 kernel/exit.c:966 do_group_exit+0xd3/0x2a0 kernel/exit.c:1107 __do_sys_exit_group kernel/exit.c:1118 [inline] __se_sys_exit_group kernel/exit.c:1116 [inline] __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1116 x64_sys_call+0x150b/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fad1cf8f749 Code: Unable to access opcode bytes at 0x7fad1cf8f71f. RSP: 002b:00007fff406dc9b8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fad1cf8f749 RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 00007fff406dca1c R08: 0000001c406dcaaf R09: 00000000000927c0 R10: 00000000000384cc R11: 0000000000000246 R12: 00000000000000f3 R13: 00000000000927c0 R14: 0000000000107f2c R15: 00007fff406dca70