======================================================
WARNING: possible circular locking dependency detected
5.7.0-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/16850 is trying to acquire lock:
ffffffff892e6e60 (console_owner){-.-.}-{0:0}, at: console_trylock_spinning+0x121/0x380 kernel/printk/printk.c:1767

but task is already holding lock:
ffffffff8c0a8f90 (&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+0x169/0x480 kernel/locking/lockdep.c:4959
       __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:1828
       serial8250_handle_irq+0x2fd/0x3e0 drivers/tty/serial/8250/8250_port.c:1915
       serial8250_default_handle_irq+0xac/0x190 drivers/tty/serial/8250/8250_port.c:1931
       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:830
       generic_handle_irq_desc include/linux/irqdesc.h:156 [inline]
       do_IRQ+0xf6/0x1d0 arch/x86/kernel/irq.c:250
       ret_from_intr+0x0/0x2b
       arch_local_irq_restore arch/x86/include/asm/paravirt.h:765 [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:408 [inline]
       uart_write+0x7d3/0x9c0 drivers/tty/serial/serial_core.c:616
       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:718 [inline]
       do_iter_write+0x402/0x540 fs/read_write.c:1001
       vfs_writev fs/read_write.c:1072 [inline]
       do_writev+0x23f/0x4a0 fs/read_write.c:1115
       do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
       entry_SYSCALL_64_after_hwframe+0x49/0xb3

-> #1 (&port->lock){-.-.}-{2:2}:
       lock_acquire+0x169/0x480 kernel/locking/lockdep.c:4959
       __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/0xd50 drivers/tty/serial/8250/8250_port.c:3240
       call_console_drivers kernel/printk/printk.c:1825 [inline]
       console_unlock+0x90c/0xec0 kernel/printk/printk.c:2515
       vprintk_emit+0x1f8/0x3c0 kernel/printk/printk.c:2032
       printk+0x62/0x83 kernel/printk/printk.c:2092
       register_console+0x7ca/0xad0 kernel/printk/printk.c:2868
       univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:690
       console_init+0x52/0x97 kernel/printk/printk.c:2968
       start_kernel+0x426/0x777 init/main.c:969
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242

-> #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+0x1b09/0x8920 kernel/locking/lockdep.c:3218
       __lock_acquire+0x116c/0x2c30 kernel/locking/lockdep.c:4380
       lock_acquire+0x169/0x480 kernel/locking/lockdep.c:4959
       console_trylock_spinning+0x141/0x380 kernel/printk/printk.c:1784
       vprintk_emit+0x1db/0x3c0 kernel/printk/printk.c:2031
       printk+0x62/0x83 kernel/printk/printk.c:2092
       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+0x40a/0x1100 drivers/tty/tty_io.c:1679
       __fput+0x2ed/0x750 fs/file_table.c:281
       task_work_run+0x147/0x1d0 kernel/task_work.c:123
       tracehook_notify_resume include/linux/tracehook.h:188 [inline]
       exit_to_usermode_loop arch/x86/entry/common.c:165 [inline]
       prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:196
       entry_SYSCALL_64_after_hwframe+0x49/0xb3

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 ***

2 locks held by syz-executor.4/16850:
 #0: ffff8880a86fb1c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_release+0xb3/0x1100 drivers/tty/tty_io.c:1661
 #1: ffffffff8c0a8f90 (&port->lock#2){-.-.}-{2:2}, at: tty_port_close_start+0x58/0x550 drivers/tty/tty_port.c:567

stack backtrace:
CPU: 0 PID: 16850 Comm: syz-executor.4 Not tainted 5.7.0-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+0x1e9/0x30e 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+0x1b09/0x8920 kernel/locking/lockdep.c:3218
 __lock_acquire+0x116c/0x2c30 kernel/locking/lockdep.c:4380
 lock_acquire+0x169/0x480 kernel/locking/lockdep.c:4959
 console_trylock_spinning+0x141/0x380 kernel/printk/printk.c:1784
 vprintk_emit+0x1db/0x3c0 kernel/printk/printk.c:2031
 printk+0x62/0x83 kernel/printk/printk.c:2092
 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+0x40a/0x1100 drivers/tty/tty_io.c:1679
 __fput+0x2ed/0x750 fs/file_table.c:281
 task_work_run+0x147/0x1d0 kernel/task_work.c:123
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:165 [inline]
 prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:196
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x416651
Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 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:00007fffa43a67e0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 000000000000000a RCX: 0000000000416651
RDX: 0000000000000000 RSI: 0000000000000081 RDI: 0000000000000009
RBP: 0000000000000000 R08: 0000000000792928 R09: 0000000000000000
R10: 00007fffa43a68c0 R11: 0000000000000293 R12: 0000000000792930
R13: 0000000000000002 R14: ffffffffffffffff R15: 000000000078c04c