====================================================== WARNING: possible circular locking dependency detected 5.6.0-rc5-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor277/11281 is trying to acquire lock: ffffffff890d8038 (console_owner){-.-.}, at: console_lock_spinning_enable+0x2d/0x60 kernel/printk/printk.c:1651 but task is already holding lock: ffffffff8bde3b38 (&(&port->lock)->rlock){-.-.}, 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)->rlock){-.-.}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 __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:1760 serial8250_handle_irq+0x25d/0x300 drivers/tty/serial/8250/8250_port.c:1833 serial8250_default_handle_irq+0xac/0x190 drivers/tty/serial/8250/8250_port.c:1849 serial8250_interrupt+0x93/0x180 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0xfc/0x550 kernel/irq/handle.c:149 handle_irq_event_percpu kernel/irq/handle.c:189 [inline] handle_irq_event+0xbd/0x280 kernel/irq/handle.c:206 handle_edge_irq+0x245/0xbf0 kernel/irq/chip.c:830 generic_handle_irq_desc include/linux/irqdesc.h:156 [inline] do_IRQ+0xf6/0x1e0 arch/x86/kernel/irq.c:250 ret_from_intr+0x0/0x36 native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60 arch_safe_halt arch/x86/include/asm/paravirt.h:144 [inline] default_idle+0x4c/0x70 arch/x86/kernel/process.c:695 cpuidle_idle_call kernel/sched/idle.c:154 [inline] do_idle+0x1ee/0x650 kernel/sched/idle.c:269 cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:361 start_secondary+0x381/0x410 arch/x86/kernel/smpboot.c:264 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242 -> #1 (&port_lock_key){-.-.}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 __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+0x17c/0xc80 drivers/tty/serial/8250/8250_port.c:3146 call_console_drivers kernel/printk/printk.c:1789 [inline] console_unlock+0x90c/0xec0 kernel/printk/printk.c:2473 vprintk_emit+0x1f8/0x3b0 kernel/printk/printk.c:1996 printk+0x62/0x83 kernel/printk/printk.c:2056 register_console+0xb6a/0xef0 kernel/printk/printk.c:2798 univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:681 console_init+0x52/0x97 kernel/printk/printk.c:2884 start_kernel+0x426/0x774 init/main.c:926 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242 -> #0 (console_owner){-.-.}: check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2970 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3954 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 console_lock_spinning_enable+0x52/0x60 kernel/printk/printk.c:1654 console_unlock+0x73f/0xec0 kernel/printk/printk.c:2470 vprintk_emit+0x1f8/0x3b0 kernel/printk/printk.c:1996 printk+0x62/0x83 kernel/printk/printk.c:2056 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:1683 __fput+0x2d8/0x730 fs/file_table.c:280 task_work_run+0x176/0x1b0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop arch/x86/entry/common.c:164 [inline] prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:195 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: console_owner --> &port_lock_key --> &(&port->lock)->rlock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&port->lock)->rlock); lock(&port_lock_key); lock(&(&port->lock)->rlock); lock(console_owner); *** DEADLOCK *** 3 locks held by syz-executor277/11281: #0: ffff888094a91198 (&tty->legacy_mutex){+.+.}, at: tty_release+0xb3/0x1100 drivers/tty/tty_io.c:1665 #1: ffffffff8bde3b38 (&(&port->lock)->rlock){-.-.}, at: tty_port_close_start+0x58/0x550 drivers/tty/tty_port.c:567 #2: ffffffff890d7f38 (console_lock){+.+.}, at: vprintk_emit+0x1db/0x3b0 kernel/printk/printk.c:1995 stack backtrace: CPU: 1 PID: 11281 Comm: syz-executor277 Not tainted 5.6.0-rc5-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+0xc3f/0xe70 kernel/locking/lockdep.c:1684 check_noncircular+0x1fb/0x3a0 kernel/locking/lockdep.c:1808 check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2970 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3954 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 console_lock_spinning_enable+0x52/0x60 kernel/printk/printk.c:1654 console_unlock+0x73f/0xec0 kernel/printk/printk.c:2470 vprintk_emit+0x1f8/0x3b0 kernel/printk/printk.c:1996 printk+0x62/0x83 kernel/printk/printk.c:2056 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:1683 __fput+0x2d8/0x730 fs/file_table.c:280 task_work_run+0x176/0x1b0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop arch/x86/entry/common.c:164 [inline] prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:195 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x409621 Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 24 1a 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:00007fff0dacd1e0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000409621 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 00000000006e7a10 R08: 00000000004b35a6 R09: 00000000004b35a6 R10: 00007fff0dacd210 R11: 0000000000000293 R12: 00000000006e7a1c R13: 0000000000000001 R14: 000000000000002d R15: 20c49ba5e353f7cf