======================================================
WARNING: possible circular locking dependency detected
5.11.0-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor100/8600 is trying to acquire lock:
ffffffff8bc82ca0 (console_owner){....}-{0:0}, at: console_unlock+0x2fb/0xbb0 kernel/printk/printk.c:2545

but task is already holding lock:
ffffffff906b3358 (&port->lock){-.-.}-{2:2}, at: tty_port_close_start.part.0+0x28/0x550 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}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
       tty_port_tty_get+0x1f/0x100 drivers/tty/tty_port.c:288
       tty_port_default_wakeup+0x11/0x40 drivers/tty/tty_port.c:47
       serial8250_tx_chars+0x487/0xa80 drivers/tty/serial/8250/8250_port.c:1832
       __start_tx drivers/tty/serial/8250/8250_port.c:1573 [inline]
       serial8250_start_tx+0x63a/0x9e0 drivers/tty/serial/8250/8250_port.c:1666
       __uart_start.isra.0+0x16d/0x1c0 drivers/tty/serial/serial_core.c:127
       uart_write+0x2fb/0x570 drivers/tty/serial/serial_core.c:614
       do_output_char+0x5de/0x850 drivers/tty/n_tty.c:448
       process_output drivers/tty/n_tty.c:515 [inline]
       n_tty_write+0x4c3/0xfd0 drivers/tty/n_tty.c:2344
       do_tty_write drivers/tty/tty_io.c:961 [inline]
       file_tty_write.constprop.0+0x521/0x8f0 drivers/tty/tty_io.c:1048
       redirected_tty_write+0xa1/0xc0 drivers/tty/tty_io.c:1055
       call_write_iter include/linux/fs.h:1901 [inline]
       do_iter_readv_writev+0x46f/0x740 fs/read_write.c:740
       do_iter_write+0x188/0x670 fs/read_write.c:866
       vfs_writev+0x1aa/0x620 fs/read_write.c:939
       do_writev+0x139/0x300 fs/read_write.c:982
       do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #1 (&port_lock_key){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:159
       serial8250_console_write+0x880/0xa90 drivers/tty/serial/8250/8250_port.c:3292
       call_console_drivers kernel/printk/printk.c:1856 [inline]
       console_unlock+0x841/0xbb0 kernel/printk/printk.c:2570
       vprintk_emit+0x189/0x490 kernel/printk/printk.c:2092
       vprintk_func+0x8d/0x1e0 kernel/printk/printk_safe.c:393
       printk+0xba/0xed kernel/printk/printk.c:2140
       register_console kernel/printk/printk.c:2921 [inline]
       register_console+0x5d1/0x800 kernel/printk/printk.c:2801
       univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:690
       console_init+0x3c7/0x596 kernel/printk/printk.c:3021
       start_kernel+0x2fc/0x48c 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 kernel/locking/lockdep.c:2993 [inline]
       validate_chain kernel/locking/lockdep.c:3608 [inline]
       __lock_acquire+0x2b26/0x54f0 kernel/locking/lockdep.c:4832
       lock_acquire kernel/locking/lockdep.c:5442 [inline]
       lock_acquire+0x1a8/0x720 kernel/locking/lockdep.c:5407
       console_lock_spinning_enable kernel/printk/printk.c:1708 [inline]
       console_unlock+0x37a/0xbb0 kernel/printk/printk.c:2567
       vprintk_emit+0x189/0x490 kernel/printk/printk.c:2092
       vprintk_func+0x8d/0x1e0 kernel/printk/printk_safe.c:393
       printk+0xba/0xed kernel/printk/printk.c:2140
       tty_port_close_start.part.0+0x503/0x550 drivers/tty/tty_port.c:569
       tty_port_close_start drivers/tty/tty_port.c:641 [inline]
       tty_port_close+0x46/0x170 drivers/tty/tty_port.c:634
       tty_release+0x45e/0x1210 drivers/tty/tty_io.c:1694
       __fput+0x283/0x920 fs/file_table.c:280
       task_work_run+0xdd/0x190 kernel/task_work.c:140
       tracehook_notify_resume include/linux/tracehook.h:189 [inline]
       exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
       exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:201
       __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
       syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294
       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-executor100/8600:
 #0: ffff8880163111c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_lock+0xbd/0x120 drivers/tty/tty_mutex.c:19
 #1: ffffffff906b3358 (&port->lock){-.-.}-{2:2}, at: tty_port_close_start.part.0+0x28/0x550 drivers/tty/tty_port.c:567
 #2: ffffffff8bd63020 (console_lock){+.+.}-{0:0}, at: vprintk_func+0x8d/0x1e0 kernel/printk/printk_safe.c:393

stack backtrace:
CPU: 0 PID: 8600 Comm: syz-executor100 Not tainted 5.11.0-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2117
 check_prev_add kernel/locking/lockdep.c:2868 [inline]
 check_prevs_add kernel/locking/lockdep.c:2993 [inline]
 validate_chain kernel/locking/lockdep.c:3608 [inline]
 __lock_acquire+0x2b26/0x54f0 kernel/locking/lockdep.c:4832
 lock_acquire kernel/locking/lockdep.c:5442 [inline]
 lock_acquire+0x1a8/0x720 kernel/locking/lockdep.c:5407
 console_lock_spinning_enable kernel/printk/printk.c:1708 [inline]
 console_unlock+0x37a/0xbb0 kernel/printk/printk.c:2567
 vprintk_emit+0x189/0x490 kernel/printk/printk.c:2092
 vprintk_func+0x8d/0x1e0 kernel/printk/printk_safe.c:393
 printk+0xba/0xed kernel/printk/printk.c:2140
 tty_port_close_start.part.0+0x503/0x550 drivers/tty/tty_port.c:569
 tty_port_close_start drivers/tty/tty_port.c:641 [inline]
 tty_port_close+0x46/0x170 drivers/tty/tty_port.c:634
 tty_release+0x45e/0x1210 drivers/tty/tty_io.c:1694
 __fput+0x283/0x920 fs/file_table.c:280
 task_work_run+0xdd/0x190 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:174 [inline]
 exit_to_user_mode_prepare+0x249/0x250 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x40667b
Code: 0f 05 48 3d 00 f0 ff ff 77 45 c3 0f 1f 40 00 48 83 ec 18 89 7c 24 0c e8 03 fd ff ff 8b 7c 24 0c 41 89 c0 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 35 44 89 c7 89 44 24 0c e8 41 fd ff ff 8b 44
RSP: 002b:00007ffc3a9349f0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 000000000040667b
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000004ca41c R08: 0000000000000000 R09: 0000000100000000
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000032
R13: 00007ffc3a934a40 R14: 00007ffc3a934a90 R15: 0000000000000002