======================================================
WARNING: possible circular locking dependency detected
5.7.0-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.5/402 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:
ffff8880888a1158 (&port->lock#2){-.-.}-{2:2}, at: pty_write+0xb6/0x180 drivers/tty/pty.c:120

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
       native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60
       arch_safe_halt arch/x86/include/asm/paravirt.h:150 [inline]
       acpi_safe_halt+0x87/0xe0 drivers/acpi/processor_idle.c:111
       acpi_idle_do_entry drivers/acpi/processor_idle.c:525 [inline]
       acpi_idle_enter+0x3f4/0xac0 drivers/acpi/processor_idle.c:651
       cpuidle_enter_state+0x2d7/0x7b0 drivers/cpuidle/cpuidle.c:234
       cpuidle_enter+0x59/0x90 drivers/cpuidle/cpuidle.c:345
       call_cpuidle kernel/sched/idle.c:117 [inline]
       cpuidle_idle_call kernel/sched/idle.c:207 [inline]
       do_idle+0x49c/0x650 kernel/sched/idle.c:269
       cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:365
       start_secondary+0x213/0x240 arch/x86/kernel/smpboot.c:268
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242

-> #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
       fail_dump lib/fault-inject.c:45 [inline]
       should_fail+0x414/0x5b0 lib/fault-inject.c:144
       should_failslab+0x5/0x20 mm/slab_common.c:1790
       slab_pre_alloc_hook mm/slab.h:569 [inline]
       slab_alloc mm/slab.c:3306 [inline]
       __do_kmalloc mm/slab.c:3654 [inline]
       __kmalloc+0x74/0x330 mm/slab.c:3665
       kmalloc include/linux/slab.h:560 [inline]
       tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline]
       __tty_buffer_request_room+0x1f3/0x540 drivers/tty/tty_buffer.c:273
       tty_insert_flip_string_fixed_flag+0x91/0x2c0 drivers/tty/tty_buffer.c:318
       tty_insert_flip_string include/linux/tty_flip.h:37 [inline]
       pty_write+0xda/0x180 drivers/tty/pty.c:122
       do_output_char+0x63b/0x940 drivers/tty/n_tty.c:447
       __process_echoes+0x2a3/0x930 drivers/tty/n_tty.c:739
       flush_echoes drivers/tty/n_tty.c:829 [inline]
       __receive_buf drivers/tty/n_tty.c:1648 [inline]
       n_tty_receive_buf_common+0x29fa/0x3100 drivers/tty/n_tty.c:1742
       tiocsti drivers/tty/tty_io.c:2196 [inline]
       tty_ioctl+0xd5b/0x15c0 drivers/tty/tty_io.c:2572
       vfs_ioctl fs/ioctl.c:47 [inline]
       ksys_ioctl fs/ioctl.c:771 [inline]
       __do_sys_ioctl fs/ioctl.c:780 [inline]
       __se_sys_ioctl+0xf9/0x160 fs/ioctl.c:778
       do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
       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 ***

4 locks held by syz-executor.5/402:
 #0: ffff88809ab44098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:267
 #1: ffff88809ab442e8 (&o_tty->termios_rwsem/1){++++}-{3:3}, at: n_tty_receive_buf_common+0x88/0x3100 drivers/tty/n_tty.c:1705
 #2: ffffc9000167b378 (&ldata->output_lock){+.+.}-{3:3}, at: flush_echoes drivers/tty/n_tty.c:827 [inline]
 #2: ffffc9000167b378 (&ldata->output_lock){+.+.}-{3:3}, at: __receive_buf drivers/tty/n_tty.c:1648 [inline]
 #2: ffffc9000167b378 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_receive_buf_common+0x29bb/0x3100 drivers/tty/n_tty.c:1742
 #3: ffff8880888a1158 (&port->lock#2){-.-.}-{2:2}, at: pty_write+0xb6/0x180 drivers/tty/pty.c:120

stack backtrace:
CPU: 1 PID: 402 Comm: syz-executor.5 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
 fail_dump lib/fault-inject.c:45 [inline]
 should_fail+0x414/0x5b0 lib/fault-inject.c:144
 should_failslab+0x5/0x20 mm/slab_common.c:1790
 slab_pre_alloc_hook mm/slab.h:569 [inline]
 slab_alloc mm/slab.c:3306 [inline]
 __do_kmalloc mm/slab.c:3654 [inline]
 __kmalloc+0x74/0x330 mm/slab.c:3665
 kmalloc include/linux/slab.h:560 [inline]
 tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline]
 __tty_buffer_request_room+0x1f3/0x540 drivers/tty/tty_buffer.c:273
 tty_insert_flip_string_fixed_flag+0x91/0x2c0 drivers/tty/tty_buffer.c:318
 tty_insert_flip_string include/linux/tty_flip.h:37 [inline]
 pty_write+0xda/0x180 drivers/tty/pty.c:122
 do_output_char+0x63b/0x940 drivers/tty/n_tty.c:447
 __process_echoes+0x2a3/0x930 drivers/tty/n_tty.c:739
 flush_echoes drivers/tty/n_tty.c:829 [inline]
 __receive_buf drivers/tty/n_tty.c:1648 [inline]
 n_tty_receive_buf_common+0x29fa/0x3100 drivers/tty/n_tty.c:1742
 tiocsti drivers/tty/tty_io.c:2196 [inline]
 tty_ioctl+0xd5b/0x15c0 drivers/tty/tty_io.c:2572
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl fs/ioctl.c:771 [inline]
 __do_sys_ioctl fs/ioctl.c:780 [inline]
 __se_sys_ioctl+0xf9/0x160 fs/ioctl.c:778
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45ca69
Code: 0d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f9fd11a3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004eea00 RCX: 000000000045ca69
RDX: 0000000020000100 RSI: 0000000000005412 RDI: 0000000000000004
RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000005
R13: 0000000000000560 R14: 00000000004c81ab R15: 00007f9fd11a46d4