====================================================== WARNING: possible circular locking dependency detected 5.7.0-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/16850 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: ffffffff8c0a8f90 (&port->lock#2){-.-.}-{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){-.-.}-{2:2}: 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 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+0x7d3/0x9c0 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+0xf3/0x1b0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 -> #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 tty_port_close_start+0x3c8/0x550 drivers/tty/tty_port.c:569 tty_port_close+0x25/0x140 drivers/tty/tty_port.c:634 tty_release+0x40a/0x1100 drivers/tty/tty_io.c:1679 __fput+0x2ed/0x750 fs/file_table.c:281 task_work_run+0x147/0x1d0 kernel/task_work.c:123 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop arch/x86/entry/common.c:165 [inline] prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:196 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 *** 2 locks held by syz-executor.4/16850: #0: ffff8880a86fb1c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_release+0xb3/0x1100 drivers/tty/tty_io.c:1661 #1: ffffffff8c0a8f90 (&port->lock#2){-.-.}-{2:2}, at: tty_port_close_start+0x58/0x550 drivers/tty/tty_port.c:567 stack backtrace: CPU: 0 PID: 16850 Comm: syz-executor.4 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 tty_port_close_start+0x3c8/0x550 drivers/tty/tty_port.c:569 tty_port_close+0x25/0x140 drivers/tty/tty_port.c:634 tty_release+0x40a/0x1100 drivers/tty/tty_io.c:1679 __fput+0x2ed/0x750 fs/file_table.c:281 task_work_run+0x147/0x1d0 kernel/task_work.c:123 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop arch/x86/entry/common.c:165 [inline] prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:196 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x416651 Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01 RSP: 002b:00007fffa43a67e0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 000000000000000a RCX: 0000000000416651 RDX: 0000000000000000 RSI: 0000000000000081 RDI: 0000000000000009 RBP: 0000000000000000 R08: 0000000000792928 R09: 0000000000000000 R10: 00007fffa43a68c0 R11: 0000000000000293 R12: 0000000000792930 R13: 0000000000000002 R14: ffffffffffffffff R15: 000000000078c04c