====================================================== WARNING: possible circular locking dependency detected 5.9.0-rc6-next-20200924-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor486/14691 is trying to acquire lock: ffffffff8a465260 (console_owner){..-.}-{0:0}, at: console_unlock+0x36a/0xd20 kernel/printk/printk.c:2467 but task is already holding lock: ffffffff8e5baaf8 (&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+0x94/0xd0 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 serial8250_handle_irq.part.0+0x328/0x3d0 drivers/tty/serial/8250/8250_port.c:1919 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1892 [inline] serial8250_default_handle_irq+0xb2/0x220 drivers/tty/serial/8250/8250_port.c:1935 serial8250_interrupt+0xe6/0x190 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x20b/0x9e0 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0x102/0x290 kernel/irq/handle.c:213 handle_edge_irq+0x25f/0xd00 kernel/irq/chip.c:819 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:786 __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+0x115/0x1f0 arch/x86/kernel/irq.c:239 asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:622 arch_local_irq_restore arch/x86/include/asm/paravirt.h:653 [inline] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline] _raw_spin_unlock_irqrestore+0x4d/0x90 kernel/locking/spinlock.c:191 spin_unlock_irqrestore include/linux/spinlock.h:409 [inline] uart_write+0x30d/0x570 drivers/tty/serial/serial_core.c:615 do_output_char+0x5de/0x850 drivers/tty/n_tty.c:447 process_output drivers/tty/n_tty.c:514 [inline] n_tty_write+0x481/0xf80 drivers/tty/n_tty.c:2345 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x4d9/0x870 drivers/tty/tty_io.c:1046 redirected_tty_write+0xaa/0xb0 drivers/tty/tty_io.c:1067 do_loop_readv_writev fs/read_write.c:754 [inline] do_loop_readv_writev fs/read_write.c:738 [inline] do_iter_write+0x489/0x670 fs/read_write.c:1037 vfs_writev+0x1aa/0x2e0 fs/read_write.c:1108 do_writev+0x139/0x300 fs/read_write.c:1151 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+0x94/0xd0 kernel/locking/spinlock.c:159 serial8250_console_write+0x200/0xb30 drivers/tty/serial/8250/8250_port.c:3289 call_console_drivers kernel/printk/printk.c:1878 [inline] console_unlock+0xac0/0xd20 kernel/printk/printk.c:2492 vprintk_emit+0x2a6/0x6e0 kernel/printk/printk.c:2021 vprintk_func+0x8d/0x1e0 kernel/printk/printk_safe.c:393 printk+0xba/0xed kernel/printk/printk.c:2069 register_console kernel/printk/printk.c:2843 [inline] register_console+0x55f/0x810 kernel/printk/printk.c:2723 univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:690 console_init+0x3c7/0x596 kernel/printk/printk.c:2943 start_kernel+0x31c/0x4b1 init/main.c:976 secondary_startup_64_no_verify+0xa6/0xab -> #0 (console_owner){..-.}-{0:0}: check_prev_add kernel/locking/lockdep.c:2819 [inline] check_prevs_add kernel/locking/lockdep.c:2944 [inline] validate_chain kernel/locking/lockdep.c:3562 [inline] __lock_acquire+0x285b/0x56d0 kernel/locking/lockdep.c:4796 lock_acquire+0x1f2/0xaa0 kernel/locking/lockdep.c:5398 console_lock_spinning_enable kernel/printk/printk.c:1730 [inline] console_unlock+0x3e9/0xd20 kernel/printk/printk.c:2489 vprintk_emit+0x2a6/0x6e0 kernel/printk/printk.c:2021 vprintk_func+0x8d/0x1e0 kernel/printk/printk_safe.c:393 printk+0xba/0xed kernel/printk/printk.c:2069 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+0x455/0xf60 drivers/tty/tty_io.c:1679 __fput+0x285/0x920 fs/file_table.c:281 task_work_run+0xdd/0x190 kernel/task_work.c:141 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_user_mode_loop kernel/entry/common.c:165 [inline] exit_to_user_mode_prepare+0x1e2/0x1f0 kernel/entry/common.c:192 syscall_exit_to_user_mode+0x7a/0x2c0 kernel/entry/common.c:267 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-executor486/14691: #0: ffff8880a2b9c1c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_lock+0xbd/0x120 drivers/tty/tty_mutex.c:19 #1: ffffffff8e5baaf8 (&port->lock){-.-.}-{2:2}, at: tty_port_close_start.part.0+0x28/0x550 drivers/tty/tty_port.c:567 #2: ffffffff8a5455e0 (console_lock){+.+.}-{0:0}, at: vprintk_func+0x8d/0x1e0 kernel/printk/printk_safe.c:393 stack backtrace: CPU: 0 PID: 14691 Comm: syz-executor486 Not tainted 5.9.0-rc6-next-20200924-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+0x198/0x1fb lib/dump_stack.c:118 check_noncircular+0x25d/0x2e0 kernel/locking/lockdep.c:2070 check_prev_add kernel/locking/lockdep.c:2819 [inline] check_prevs_add kernel/locking/lockdep.c:2944 [inline] validate_chain kernel/locking/lockdep.c:3562 [inline] __lock_acquire+0x285b/0x56d0 kernel/locking/lockdep.c:4796 lock_acquire+0x1f2/0xaa0 kernel/locking/lockdep.c:5398 console_lock_spinning_enable kernel/printk/printk.c:1730 [inline] console_unlock+0x3e9/0xd20 kernel/printk/printk.c:2489 vprintk_emit+0x2a6/0x6e0 kernel/printk/printk.c:2021 vprintk_func+0x8d/0x1e0 kernel/printk/printk_safe.c:393 printk+0xba/0xed kernel/printk/printk.c:2069 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+0x455/0xf60 drivers/tty/tty_io.c:1679 __fput+0x285/0x920 fs/file_table.c:281 task_work_run+0xdd/0x190 kernel/task_work.c:141 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_user_mode_loop kernel/entry/common.c:165 [inline] exit_to_user_mode_prepare+0x1e2/0x1f0 kernel/entry/common.c:192 syscall_exit_to_user_mode+0x7a/0x2c0 kernel/entry/common.c:267 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x4057f1 Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 19 00 00 c3 48 83 ec 08 e8 6a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 b3 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01 RSP: 002b:00007ffc12958cf0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00000000004057f1 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 0000000000000002 R08: 0000000120080522 R09: 0000000120080522 R10: 00007ffc12958d10 R11: 0000000000000293 R12: 00000000006dbc3c R13: 000000000000002d R14: 0000000000000064 R15: 0000000000000000