======================================================
WARNING: possible circular locking dependency detected
5.8.0-rc3-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.4/18750 is trying to acquire lock:
ffffffff892e7940 (console_owner){-.-.}-{0:0}, at: console_trylock_spinning+0x11a/0x380 kernel/printk/printk.c:1756

but task is already holding lock:
ffff8880a1736158 (&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+0x160/0x720 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:1831
       serial8250_handle_irq+0x2fd/0x3e0 drivers/tty/serial/8250/8250_port.c:1918
       serial8250_default_handle_irq+0xac/0x190 drivers/tty/serial/8250/8250_port.c:1934
       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
       asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
       __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+0x155/0x260 arch/x86/kernel/irq.c:239
       asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:587
       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+0x767/0x8f0 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+0x73/0xe0 arch/x86/entry/common.c:359
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #1 (&port->lock){-.-.}-{2:2}:
       lock_acquire+0x160/0x720 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/0xd60 drivers/tty/serial/8250/8250_port.c:3245
       call_console_drivers kernel/printk/printk.c:1814 [inline]
       console_unlock+0x90c/0xec0 kernel/printk/printk.c:2493
       vprintk_emit+0x1f8/0x3c0 kernel/printk/printk.c:2021
       printk+0x62/0x83 kernel/printk/printk.c:2070
       register_console+0x7ca/0xad0 kernel/printk/printk.c:2846
       univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:690
       console_init+0x52/0x97 kernel/printk/printk.c:2946
       start_kernel+0x426/0x777 init/main.c:970
       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/0x8920 kernel/locking/lockdep.c:3218
       __lock_acquire+0x116c/0x2c30 kernel/locking/lockdep.c:4380
       lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959
       console_trylock_spinning+0x13a/0x380 kernel/printk/printk.c:1773
       vprintk_emit+0x1db/0x3c0 kernel/printk/printk.c:2020
       printk+0x62/0x83 kernel/printk/printk.c:2070
       fail_dump lib/fault-inject.c:45 [inline]
       should_fail+0x36c/0x4e0 lib/fault-inject.c:146
       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
       process_output_block drivers/tty/n_tty.c:595 [inline]
       n_tty_write+0xcbf/0x1170 drivers/tty/n_tty.c:2333
       do_tty_write drivers/tty/tty_io.c:962 [inline]
       tty_write+0x593/0x940 drivers/tty/tty_io.c:1046
       __vfs_write+0x9c/0x6e0 fs/read_write.c:495
       vfs_write+0x274/0x580 fs/read_write.c:559
       ksys_write+0x11b/0x220 fs/read_write.c:612
       do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:359
       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 ***

5 locks held by syz-executor.4/18750:
 #0: ffff88802b333098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:267
 #1: ffff88802b333130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:888 [inline]
 #1: ffff88802b333130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: do_tty_write drivers/tty/tty_io.c:911 [inline]
 #1: ffff88802b333130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write+0x22c/0x940 drivers/tty/tty_io.c:1046
 #2: ffff88802b3332e8 (&o_tty->termios_rwsem/1){++++}-{3:3}, at: n_tty_write+0xf15/0x1170 drivers/tty/n_tty.c:2378
 #3: ffffc90000f30378 (&ldata->output_lock){+.+.}-{3:3}, at: process_output_block drivers/tty/n_tty.c:550 [inline]
 #3: ffffc90000f30378 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_write+0x613/0x1170 drivers/tty/n_tty.c:2333
 #4: ffff8880a1736158 (&port->lock#2){-.-.}-{2:2}, at: pty_write+0xb6/0x180 drivers/tty/pty.c:120

stack backtrace:
CPU: 0 PID: 18750 Comm: syz-executor.4 Not tainted 5.8.0-rc3-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/0x8920 kernel/locking/lockdep.c:3218
 __lock_acquire+0x116c/0x2c30 kernel/locking/lockdep.c:4380
 lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959
 console_trylock_spinning+0x13a/0x380 kernel/printk/printk.c:1773
 vprintk_emit+0x1db/0x3c0 kernel/printk/printk.c:2020
 printk+0x62/0x83 kernel/printk/printk.c:2070
 fail_dump lib/fault-inject.c:45 [inline]
 should_fail+0x36c/0x4e0 lib/fault-inject.c:146
 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
 process_output_block drivers/tty/n_tty.c:595 [inline]
 n_tty_write+0xcbf/0x1170 drivers/tty/n_tty.c:2333
 do_tty_write drivers/tty/tty_io.c:962 [inline]
 tty_write+0x593/0x940 drivers/tty/tty_io.c:1046
 __vfs_write+0x9c/0x6e0 fs/read_write.c:495
 vfs_write+0x274/0x580 fs/read_write.c:559
 ksys_write+0x11b/0x220 fs/read_write.c:612
 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45cb29
Code: Bad RIP value.
RSP: 002b:00007faa65126c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000050cd20 RCX: 000000000045cb29
RDX: 00000000ffffffde RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 000000000078bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000000a
R13: 0000000000000cda R14: 00000000004cf3a8 R15: 00007faa651276d4