====================================================== WARNING: possible circular locking dependency detected 5.6.0-rc7-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.2/10405 is trying to acquire lock: ffffffff897a1be0 (console_owner){-...}, at: console_trylock_spinning kernel/printk/printk.c:1724 [inline] ffffffff897a1be0 (console_owner){-...}, at: vprintk_emit+0x405/0x710 kernel/printk/printk.c:1995 but task is already holding lock: ffffffff8cec3560 (&(&port->lock)->rlock){-.-.}, 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)->rlock){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x8c/0xbf 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+0x48f/0xae0 drivers/tty/serial/8250/8250_port.c:1760 serial8250_handle_irq.part.0+0x24b/0x290 drivers/tty/serial/8250/8250_port.c:1833 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1819 [inline] serial8250_default_handle_irq+0xb5/0x140 drivers/tty/serial/8250/8250_port.c:1849 serial8250_interrupt+0xe6/0x190 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x15d/0x950 kernel/irq/handle.c:149 handle_irq_event_percpu+0x76/0x160 kernel/irq/handle.c:189 handle_irq_event+0xa2/0x12d kernel/irq/handle.c:206 handle_edge_irq+0x24b/0x8c0 kernel/irq/chip.c:830 generic_handle_irq_desc include/linux/irqdesc.h:156 [inline] do_IRQ+0xd9/0x280 arch/x86/kernel/irq.c:250 ret_from_intr+0x0/0x36 arch_local_irq_restore arch/x86/include/asm/paravirt.h:759 [inline] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline] _raw_spin_unlock_irqrestore+0x8c/0xe0 kernel/locking/spinlock.c:191 spin_unlock_irqrestore include/linux/spinlock.h:393 [inline] uart_write+0x35d/0x680 drivers/tty/serial/serial_core.c:613 do_output_char+0x5dd/0x850 drivers/tty/n_tty.c:447 process_output drivers/tty/n_tty.c:514 [inline] n_tty_write+0x49e/0xf90 drivers/tty/n_tty.c:2345 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x48f/0x7f0 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:717 [inline] do_loop_readv_writev fs/read_write.c:701 [inline] do_iter_write fs/read_write.c:1000 [inline] do_iter_write+0x478/0x600 fs/read_write.c:979 vfs_writev+0x1b3/0x2f0 fs/read_write.c:1071 do_writev+0x133/0x2f0 fs/read_write.c:1114 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&port_lock_key){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159 serial8250_console_write+0x23f/0x970 drivers/tty/serial/8250/8250_port.c:3146 call_console_drivers kernel/printk/printk.c:1791 [inline] console_unlock+0xb68/0xf00 kernel/printk/printk.c:2473 vprintk_emit+0x2a7/0x710 kernel/printk/printk.c:1996 vprintk_func+0x79/0x17e kernel/printk/printk_safe.c:386 printk+0xba/0xed kernel/printk/printk.c:2056 register_console+0x719/0xb10 kernel/printk/printk.c:2798 univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:681 console_init+0x43f/0x646 kernel/printk/printk.c:2884 start_kernel+0x617/0x8a1 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 kernel/locking/lockdep.c:2970 [inline] __lock_acquire+0x201b/0x3ca0 kernel/locking/lockdep.c:3954 lock_acquire+0x197/0x420 kernel/locking/lockdep.c:4484 console_trylock_spinning kernel/printk/printk.c:1745 [inline] vprintk_emit+0x442/0x710 kernel/printk/printk.c:1995 vprintk_func+0x79/0x17e kernel/printk/printk_safe.c:386 printk+0xba/0xed kernel/printk/printk.c:2056 tty_port_close_start.part.0+0x500/0x550 drivers/tty/tty_port.c:569 tty_port_close_start drivers/tty/tty_port.c:641 [inline] tty_port_close+0x46/0xf0 drivers/tty/tty_port.c:634 tty_release+0x3b9/0xe90 drivers/tty/tty_io.c:1679 __fput+0x2da/0x850 fs/file_table.c:280 task_work_run+0x13f/0x1b0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x2fa/0x360 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] syscall_return_slowpath arch/x86/entry/common.c:278 [inline] do_syscall_64+0x6b1/0x7d0 arch/x86/entry/common.c:304 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 *** 2 locks held by syz-executor.2/10405: #0: ffff88808e924198 (&tty->legacy_mutex){+.+.}, at: tty_lock+0xbd/0x120 drivers/tty/tty_mutex.c:19 #1: ffffffff8cec3560 (&(&port->lock)->rlock){-.-.}, at: tty_port_close_start.part.0+0x28/0x550 drivers/tty/tty_port.c:567 stack backtrace: CPU: 0 PID: 10405 Comm: syz-executor.2 Not tainted 5.6.0-rc7-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+0x188/0x20d lib/dump_stack.c:118 check_noncircular+0x32e/0x3e0 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 kernel/locking/lockdep.c:2970 [inline] __lock_acquire+0x201b/0x3ca0 kernel/locking/lockdep.c:3954 lock_acquire+0x197/0x420 kernel/locking/lockdep.c:4484 console_trylock_spinning kernel/printk/printk.c:1745 [inline] vprintk_emit+0x442/0x710 kernel/printk/printk.c:1995 vprintk_func+0x79/0x17e kernel/printk/printk_safe.c:386 printk+0xba/0xed kernel/printk/printk.c:2056 tty_port_close_start.part.0+0x500/0x550 drivers/tty/tty_port.c:569 tty_port_close_start drivers/tty/tty_port.c:641 [inline] tty_port_close+0x46/0xf0 drivers/tty/tty_port.c:634 tty_release+0x3b9/0xe90 drivers/tty/tty_io.c:1679 __fput+0x2da/0x850 fs/file_table.c:280 task_work_run+0x13f/0x1b0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x2fa/0x360 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] syscall_return_slowpath arch/x86/entry/common.c:278 [inline] do_syscall_64+0x6b1/0x7d0 arch/x86/entry/common.c:304 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4163e1 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:00007fff159ead00 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00000000004163e1 RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000770148 R09: 01ffffffffffffff R10: 00007fff159eadd0 R11: 0000000000000293 R12: 000000000076bf00 R13: 0000000000770150 R14: 0000000000000000 R15: 000000000076bf0c