======================================================
WARNING: possible circular locking dependency detected
5.9.0-rc2-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor978/8231 is trying to acquire lock:
ffffffff894fc9c0 (console_owner){-.-.}-{0:0}, at: console_lock_spinning_enable+0x2d/0x60 kernel/printk/printk.c:1687

but task is already holding lock:
ffffffff8c3277a0 (&port->lock#2){-.-.}-{2:2}, at: tty_port_close_start+0x58/0x550 drivers/tty/tty_port.c:567

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&port->lock#2){-.-.}-{2:2}:
       lock_acquire+0x160/0x730 kernel/locking/lockdep.c:5005
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x9e/0xc0 kernel/locking/spinlock.c:159
       tty_port_tty_get+0x21/0xe0 drivers/tty/tty_port.c:288
       tty_port_default_wakeup+0x11/0x40 drivers/tty/tty_port.c:47
       serial8250_tx_chars+0x5ea/0x800 drivers/tty/serial/8250/8250_port.c:1832
       serial8250_handle_irq+0x2fd/0x3e0 drivers/tty/serial/8250/8250_port.c:1919
       serial8250_default_handle_irq+0xac/0x190 drivers/tty/serial/8250/8250_port.c:1935
       serial8250_interrupt+0x93/0x180 drivers/tty/serial/8250/8250_core.c:126
       __handle_irq_event_percpu+0x1b7/0x610 kernel/irq/handle.c:156
       handle_irq_event_percpu kernel/irq/handle.c:196 [inline]
       handle_irq_event+0xbd/0x280 kernel/irq/handle.c:213
       handle_edge_irq+0x245/0xbf0 kernel/irq/chip.c:819
       asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706
       __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
       run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
       handle_irq arch/x86/kernel/irq.c:230 [inline]
       __common_interrupt arch/x86/kernel/irq.c:249 [inline]
       common_interrupt+0x13c/0x230 arch/x86/kernel/irq.c:239
       asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:572
       arch_local_irq_restore arch/x86/include/asm/paravirt.h:770 [inline]
       __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline]
       _raw_spin_unlock_irqrestore+0xa5/0xd0 kernel/locking/spinlock.c:191
       spin_unlock_irqrestore include/linux/spinlock.h:409 [inline]
       uart_write+0x767/0x8f0 drivers/tty/serial/serial_core.c:615
       do_output_char+0x63b/0x940 drivers/tty/n_tty.c:447
       process_output drivers/tty/n_tty.c:514 [inline]
       n_tty_write+0xd5c/0x1170 drivers/tty/n_tty.c:2345
       do_tty_write drivers/tty/tty_io.c:962 [inline]
       tty_write+0x593/0x940 drivers/tty/tty_io.c:1046
       do_loop_readv_writev fs/read_write.c:737 [inline]
       do_iter_write+0x441/0x610 fs/read_write.c:1020
       vfs_writev fs/read_write.c:1091 [inline]
       do_writev+0x23f/0x4a0 fs/read_write.c:1134
       do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #1 (&port->lock){-.-.}-{2:2}:
       lock_acquire+0x160/0x730 kernel/locking/lockdep.c:5005
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x9e/0xc0 kernel/locking/spinlock.c:159
       serial8250_console_write+0x13e/0xd60 drivers/tty/serial/8250/8250_port.c:3286
       call_console_drivers kernel/printk/printk.c:1822 [inline]
       console_unlock+0x90c/0xec0 kernel/printk/printk.c:2501
       vprintk_emit+0x1f8/0x3c0 kernel/printk/printk.c:2029
       printk+0x62/0x83 kernel/printk/printk.c:2078
       register_console+0x7ca/0xad0 kernel/printk/printk.c:2854
       univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:690
       console_init+0x52/0x97 kernel/printk/printk.c:2954
       start_kernel+0x2db/0x4f0 init/main.c:975
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #0 (console_owner){-.-.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:2496 [inline]
       check_prevs_add kernel/locking/lockdep.c:2601 [inline]
       validate_chain+0x1b0c/0x88a0 kernel/locking/lockdep.c:3218
       __lock_acquire+0x1161/0x2ab0 kernel/locking/lockdep.c:4426
       lock_acquire+0x160/0x730 kernel/locking/lockdep.c:5005
       console_lock_spinning_enable+0x52/0x60 kernel/printk/printk.c:1690
       console_unlock+0x73f/0xec0 kernel/printk/printk.c:2498
       vprintk_emit+0x1f8/0x3c0 kernel/printk/printk.c:2029
       printk+0x62/0x83 kernel/printk/printk.c:2078
       tty_port_close_start+0x3c8/0x550 drivers/tty/tty_port.c:569
       tty_port_close+0x25/0x140 drivers/tty/tty_port.c:634
       tty_release+0x378/0xf90 drivers/tty/tty_io.c:1679
       __fput+0x34f/0x7b0 fs/file_table.c:281
       task_work_run+0x137/0x1c0 kernel/task_work.c:141
       tracehook_notify_resume include/linux/tracehook.h:188 [inline]
       exit_to_user_mode_loop kernel/entry/common.c:140 [inline]
       exit_to_user_mode_prepare+0xfa/0x1b0 kernel/entry/common.c:167
       syscall_exit_to_user_mode+0x5e/0x1a0 kernel/entry/common.c:242
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

other info that might help us debug this:

Chain exists of:
  console_owner --> &port->lock --> &port->lock#2

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&port->lock#2);
                               lock(&port->lock);
                               lock(&port->lock#2);
  lock(console_owner);

 *** DEADLOCK ***

3 locks held by syz-executor978/8231:
 #0: ffff8880a89321c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_release+0xa5/0xf90 drivers/tty/tty_io.c:1661
 #1: ffffffff8c3277a0 (&port->lock#2){-.-.}-{2:2}, at: tty_port_close_start+0x58/0x550 drivers/tty/tty_port.c:567
 #2: ffffffff894fc8a0 (console_lock){+.+.}-{0:0}, at: vprintk_emit+0x1db/0x3c0 kernel/printk/printk.c:2028

stack backtrace:
CPU: 0 PID: 8231 Comm: syz-executor978 Not tainted 5.9.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1f0/0x31e lib/dump_stack.c:118
 print_circular_bug+0xc72/0xea0 kernel/locking/lockdep.c:1703
 check_noncircular+0x1fb/0x3a0 kernel/locking/lockdep.c:1827
 check_prev_add kernel/locking/lockdep.c:2496 [inline]
 check_prevs_add kernel/locking/lockdep.c:2601 [inline]
 validate_chain+0x1b0c/0x88a0 kernel/locking/lockdep.c:3218
 __lock_acquire+0x1161/0x2ab0 kernel/locking/lockdep.c:4426
 lock_acquire+0x160/0x730 kernel/locking/lockdep.c:5005
 console_lock_spinning_enable+0x52/0x60 kernel/printk/printk.c:1690
 console_unlock+0x73f/0xec0 kernel/printk/printk.c:2498
 vprintk_emit+0x1f8/0x3c0 kernel/printk/printk.c:2029
 printk+0x62/0x83 kernel/printk/printk.c:2078
 tty_port_close_start+0x3c8/0x550 drivers/tty/tty_port.c:569
 tty_port_close+0x25/0x140 drivers/tty/tty_port.c:634
 tty_release+0x378/0xf90 drivers/tty/tty_io.c:1679
 __fput+0x34f/0x7b0 fs/file_table.c:281
 task_work_run+0x137/0x1c0 kernel/task_work.c:141
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:140 [inline]
 exit_to_user_mode_prepare+0xfa/0x1b0 kernel/entry/common.c:167
 syscall_exit_to_user_mode+0x5e/0x1a0 kernel/entry/common.c:242
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x408c51
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 24 1a 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007ffc09d66720 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000408c51
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000006e0c30 R08: 00000000004b2ad2 R09: 00000000004b2ad2
R10: 00007ffc09d66740 R11: 0000000000000293 R12: 00000000006e0c3c
R13: 0000000000000001 R14: 000000000000002d R15: 20c49ba5e353f7cf