syzbot

======================================================
WARNING: possible circular locking dependency detected
5.12.0-rc8-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor109/9942 is trying to acquire lock:
ffffffff8cd04c60 (console_owner){....}-{0:0}, at: console_lock_spinning_enable+0x2d/0x60 kernel/printk/printk.c:1711

but task is already holding lock:
ffffffff906ca918 (&port->lock){-.-.}-{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}:
       lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5511
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xb3/0x100 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+0x20a/0x6d0 kernel/irq/handle.c:156
       handle_irq_event_percpu kernel/irq/handle.c:196 [inline]
       handle_irq_event+0x10a/0x2f0 kernel/irq/handle.c:213
       handle_edge_irq+0x245/0xbe0 kernel/irq/chip.c:819
       generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
       handle_irq arch/x86/kernel/irq.c:231 [inline]
       __common_interrupt+0xce/0x1e0 arch/x86/kernel/irq.c:250
       common_interrupt+0x9c/0xc0 arch/x86/kernel/irq.c:240
       asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:623
       __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
       _raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:191
       spin_unlock_irqrestore include/linux/spinlock.h:409 [inline]
       uart_write+0x6a1/0x8f0 drivers/tty/serial/serial_core.c:615
       do_output_char+0x638/0x940 drivers/tty/n_tty.c:443
       process_output drivers/tty/n_tty.c:510 [inline]
       n_tty_write+0xe33/0x1310 drivers/tty/n_tty.c:2365
       do_tty_write drivers/tty/tty_io.c:1043 [inline]
       file_tty_write+0x5c5/0x9a0 drivers/tty/tty_io.c:1133
       do_iter_readv_writev+0x566/0x770 include/linux/fs.h:1971
       do_iter_write+0x16c/0x5f0 fs/read_write.c:866
       vfs_writev fs/read_write.c:939 [inline]
       do_writev+0x240/0x440 fs/read_write.c:982
       do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x44/0xae

-> #1 (&port_lock_key){-.-.}-{2:2}:
       lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5511
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0xb3/0x100 kernel/locking/spinlock.c:159
       serial8250_console_write+0x177/0xe40 drivers/tty/serial/8250/8250_port.c:3292
       call_console_drivers kernel/printk/printk.c:1862 [inline]
       console_unlock+0x9ca/0xf00 kernel/printk/printk.c:2576
       vprintk_emit+0x21a/0x2f0 kernel/printk/printk.c:2098
       printk+0xc0/0x103 kernel/printk/printk.c:2146
       register_console+0x8dc/0xbc0 kernel/printk/printk.c:2927
       univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:690
       console_init+0x52/0x97 kernel/printk/printk.c:3027
       start_kernel+0x30c/0x544 init/main.c:993
       secondary_startup_64_no_verify+0xb0/0xbb

-> #0 (console_owner){....}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:2937 [inline]
       check_prevs_add+0x4d6/0x5a90 kernel/locking/lockdep.c:3060
       validate_chain kernel/locking/lockdep.c:3675 [inline]
       __lock_acquire+0x4307/0x6040 kernel/locking/lockdep.c:4901
       lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5511
       console_lock_spinning_enable+0x52/0x60 kernel/printk/printk.c:1714
       console_unlock+0x711/0xf00 kernel/printk/printk.c:2573
       vprintk_emit+0x21a/0x2f0 kernel/printk/printk.c:2098
       printk+0xc0/0x103 kernel/printk/printk.c:2146
       tty_port_close_start+0x3c8/0x550 drivers/tty/tty_port.c:569
       tty_port_close+0x26/0x140 drivers/tty/tty_port.c:634
       tty_release+0x30c/0xef0 drivers/tty/tty_io.c:1779
       __fput+0x352/0x7b0 fs/file_table.c:280
       task_work_run+0x146/0x1c0 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+0x10b/0x1e0 kernel/entry/common.c:208
       __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
       syscall_exit_to_user_mode+0x26/0x70 kernel/entry/common.c:301
       entry_SYSCALL_64_after_hwframe+0x44/0xae

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-executor109/9942:
 #0: ffff88801a2ca1c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_release+0xac/0xef0 drivers/tty/tty_io.c:1761
 #1: ffffffff906ca918 (&port->lock){-.-.}-{2:2}, at: tty_port_close_start+0x58/0x550 drivers/tty/tty_port.c:567
 #2: ffffffff8cbec980 (console_lock){+.+.}-{0:0}, at: vprintk_emit+0x201/0x2f0 kernel/printk/printk.c:2097

stack backtrace:
CPU: 1 PID: 9942 Comm: syz-executor109 Not tainted 5.12.0-rc8-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+0x202/0x31e lib/dump_stack.c:120
 print_circular_bug+0xb17/0xdc0 kernel/locking/lockdep.c:2006
 check_noncircular+0x2cc/0x390 kernel/locking/lockdep.c:2128
 check_prev_add kernel/locking/lockdep.c:2937 [inline]
 check_prevs_add+0x4d6/0x5a90 kernel/locking/lockdep.c:3060
 validate_chain kernel/locking/lockdep.c:3675 [inline]
 __lock_acquire+0x4307/0x6040 kernel/locking/lockdep.c:4901
 lock_acquire+0x17f/0x720 kernel/locking/lockdep.c:5511
 console_lock_spinning_enable+0x52/0x60 kernel/printk/printk.c:1714
 console_unlock+0x711/0xf00 kernel/printk/printk.c:2573
 vprintk_emit+0x21a/0x2f0 kernel/printk/printk.c:2098
 printk+0xc0/0x103 kernel/printk/printk.c:2146
 tty_port_close_start+0x3c8/0x550 drivers/tty/tty_port.c:569
 tty_port_close+0x26/0x140 drivers/tty/tty_port.c:634
 tty_release+0x30c/0xef0 drivers/tty/tty_io.c:1779
 __fput+0x352/0x7b0 fs/file_table.c:280
 task_work_run+0x146/0x1c0 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+0x10b/0x1e0 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x26/0x70 kernel/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4098bb
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:00007fff6de75b80 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00000000004098bb
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007fff6de75c80 R08: 0000000000000000 R09: 00007fff6de75b30
R10: 0000000000000000 R11: 0000000000000293 R12: 000000000000e563
R13: 00000000004cf4dc R14: 00007fff6de75c10 R15: 00000000004cf4c0