======================================================
WARNING: possible circular locking dependency detected
5.11.0-rc7-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.3/14360 is trying to acquire lock:
ffffffff8c706140 (console_owner){-...}-{0:0}, at: console_trylock_spinning+0x114/0x260 kernel/printk/printk.c:1782

but task is already holding lock:
ffff888023e11958 (&port->lock){-.-.}-{2:2}, at: pty_write+0xb6/0x170 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}:
       lock_acquire+0x114/0x5e0 kernel/locking/lockdep.c:5442
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x73/0xa0 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+0xaf/0x190 drivers/tty/serial/8250/8250_port.c:1935
       serial8250_interrupt+0xa3/0x1e0 drivers/tty/serial/8250/8250_core.c:126
       __handle_irq_event_percpu+0x1b7/0x620 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+0x245/0xbe0 kernel/irq/chip.c:819
       asm_call_irq_on_stack+0xf/0x20
       __run_irq_on_irqstack arch/x86/include/asm/irq_stack.h:48 [inline]
       run_irq_on_irqstack_cond arch/x86/include/asm/irq_stack.h:101 [inline]
       handle_irq arch/x86/kernel/irq.c:230 [inline]
       __common_interrupt arch/x86/kernel/irq.c:249 [inline]
       common_interrupt+0x147/0x230 arch/x86/kernel/irq.c:239
       asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:620
       native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline]
       arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline]
       acpi_safe_halt drivers/acpi/processor_idle.c:110 [inline]
       acpi_idle_do_entry drivers/acpi/processor_idle.c:516 [inline]
       acpi_idle_enter+0x3c9/0x700 drivers/acpi/processor_idle.c:647
       cpuidle_enter_state+0x486/0xd50 drivers/cpuidle/cpuidle.c:237
       cpuidle_enter+0x59/0x90 drivers/cpuidle/cpuidle.c:351
       call_cpuidle kernel/sched/idle.c:158 [inline]
       cpuidle_idle_call kernel/sched/idle.c:239 [inline]
       do_idle+0x315/0x530 kernel/sched/idle.c:299
       cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:396
       start_kernel+0x494/0x53a init/main.c:1061
       secondary_startup_64_no_verify+0xb0/0xbb

-> #1 (&port_lock_key){-.-.}-{2:2}:
       lock_acquire+0x114/0x5e0 kernel/locking/lockdep.c:5442
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x73/0xa0 kernel/locking/spinlock.c:159
       serial8250_console_write+0x108/0xcc0 drivers/tty/serial/8250/8250_port.c:3292
       call_console_drivers kernel/printk/printk.c:1852 [inline]
       console_unlock+0x960/0xcf0 kernel/printk/printk.c:2570
       vprintk_emit+0x15e/0x200 kernel/printk/printk.c:2092
       printk+0x62/0x83 kernel/printk/printk.c:2140
       register_console+0x781/0xa60 kernel/printk/printk.c:2921
       univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:690
       console_init+0x52/0x97 kernel/printk/printk.c:3021
       start_kernel+0x302/0x53a init/main.c:989
       secondary_startup_64_no_verify+0xb0/0xbb

-> #0 (console_owner){-...}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:2868 [inline]
       check_prevs_add+0x353/0x5280 kernel/locking/lockdep.c:2993
       validate_chain kernel/locking/lockdep.c:3608 [inline]
       __lock_acquire+0x4227/0x5e90 kernel/locking/lockdep.c:4832
       lock_acquire+0x114/0x5e0 kernel/locking/lockdep.c:5442
       console_trylock_spinning+0x134/0x260 kernel/printk/printk.c:1799
       vprintk_emit+0x145/0x200 kernel/printk/printk.c:2091
       printk+0x62/0x83 kernel/printk/printk.c:2140
       fail_dump lib/fault-inject.c:45 [inline]
       should_fail+0x366/0x4b0 lib/fault-inject.c:146
       should_failslab+0x5/0x20 mm/slab_common.c:1195
       slab_pre_alloc_hook mm/slab.h:495 [inline]
       slab_alloc_node mm/slub.c:2817 [inline]
       slab_alloc mm/slub.c:2900 [inline]
       __kmalloc+0x84/0x330 mm/slub.c:3981
       kmalloc include/linux/slab.h:557 [inline]
       tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline]
       __tty_buffer_request_room+0x1f0/0x540 drivers/tty/tty_buffer.c:273
       tty_insert_flip_string_fixed_flag+0x92/0x2c0 drivers/tty/tty_buffer.c:318
       tty_insert_flip_string include/linux/tty_flip.h:37 [inline]
       pty_write+0xda/0x170 drivers/tty/pty.c:122
       n_hdlc_send_frames+0x34e/0xb20 drivers/tty/n_hdlc.c:289
       n_hdlc_tty_write+0x70f/0x850 drivers/tty/n_hdlc.c:540
       do_tty_write drivers/tty/tty_io.c:961 [inline]
       file_tty_write+0x5a6/0x950 drivers/tty/tty_io.c:1048
       call_write_iter include/linux/fs.h:1901 [inline]
       new_sync_write fs/read_write.c:518 [inline]
       vfs_write+0x896/0xab0 fs/read_write.c:605
       ksys_write+0x11b/0x220 fs/read_write.c:658
       do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

other info that might help us debug this:

Chain exists of:
  console_owner --> &port_lock_key --> &port->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&port->lock);
                               lock(&port_lock_key);
                               lock(&port->lock);
  lock(console_owner);

 *** DEADLOCK ***

3 locks held by syz-executor.3/14360:
 #0: ffff888075a58098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:266
 #1: ffff888075a58130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:885 [inline]
 #1: ffff888075a58130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: do_tty_write drivers/tty/tty_io.c:908 [inline]
 #1: ffff888075a58130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: file_tty_write+0x271/0x950 drivers/tty/tty_io.c:1048
 #2: ffff888023e11958 (&port->lock){-.-.}-{2:2}, at: pty_write+0xb6/0x170 drivers/tty/pty.c:120

stack backtrace:
CPU: 0 PID: 14360 Comm: syz-executor.3 Not tainted 5.11.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x137/0x1be lib/dump_stack.c:120
 print_circular_bug+0xadf/0xd80 kernel/locking/lockdep.c:1996
 check_noncircular+0x221/0x2d0 kernel/locking/lockdep.c:2117
 check_prev_add kernel/locking/lockdep.c:2868 [inline]
 check_prevs_add+0x353/0x5280 kernel/locking/lockdep.c:2993
 validate_chain kernel/locking/lockdep.c:3608 [inline]
 __lock_acquire+0x4227/0x5e90 kernel/locking/lockdep.c:4832
 lock_acquire+0x114/0x5e0 kernel/locking/lockdep.c:5442
 console_trylock_spinning+0x134/0x260 kernel/printk/printk.c:1799
 vprintk_emit+0x145/0x200 kernel/printk/printk.c:2091
 printk+0x62/0x83 kernel/printk/printk.c:2140
 fail_dump lib/fault-inject.c:45 [inline]
 should_fail+0x366/0x4b0 lib/fault-inject.c:146
 should_failslab+0x5/0x20 mm/slab_common.c:1195
 slab_pre_alloc_hook mm/slab.h:495 [inline]
 slab_alloc_node mm/slub.c:2817 [inline]
 slab_alloc mm/slub.c:2900 [inline]
 __kmalloc+0x84/0x330 mm/slub.c:3981
 kmalloc include/linux/slab.h:557 [inline]
 tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline]
 __tty_buffer_request_room+0x1f0/0x540 drivers/tty/tty_buffer.c:273
 tty_insert_flip_string_fixed_flag+0x92/0x2c0 drivers/tty/tty_buffer.c:318
 tty_insert_flip_string include/linux/tty_flip.h:37 [inline]
 pty_write+0xda/0x170 drivers/tty/pty.c:122
 n_hdlc_send_frames+0x34e/0xb20 drivers/tty/n_hdlc.c:289
 n_hdlc_tty_write+0x70f/0x850 drivers/tty/n_hdlc.c:540
 do_tty_write drivers/tty/tty_io.c:961 [inline]
 file_tty_write+0x5a6/0x950 drivers/tty/tty_io.c:1048
 call_write_iter include/linux/fs.h:1901 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x896/0xab0 fs/read_write.c:605
 ksys_write+0x11b/0x220 fs/read_write.c:658
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x465d99
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd35f86f188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465d99
RDX: 00000000fffffedf RSI: 0000000020000000 RDI: 0000000000000004
RBP: 00007fd35f86f1d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffdc23a7f7f R14: 00007fd35f86f300 R15: 0000000000022000