====================================================== WARNING: possible circular locking dependency detected 5.6.0-rc2-next-20200219-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.0/20047 is trying to acquire lock: ffffffff89ba23a0 (console_owner){-.-.}, at: console_trylock_spinning kernel/printk/printk.c:1725 [inline] ffffffff89ba23a0 (console_owner){-.-.}, at: vprintk_emit+0x3fd/0x700 kernel/printk/printk.c:1993 but task is already holding lock: ffffffff8c374d40 (&(&port->lock)->rlock){-.-.}, at: tty_port_close_start.part.0+0x2b/0x580 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+0x95/0xcd kernel/locking/spinlock.c:159 tty_port_tty_get+0x24/0x100 drivers/tty/tty_port.c:288 tty_port_default_wakeup+0x16/0x40 drivers/tty/tty_port.c:47 tty_port_tty_wakeup+0x57/0x70 drivers/tty/tty_port.c:388 uart_write_wakeup+0x46/0x70 drivers/tty/serial/serial_core.c:104 serial8250_tx_chars+0x495/0xaf0 drivers/tty/serial/8250/8250_port.c:1760 serial8250_handle_irq.part.0+0x261/0x2b0 drivers/tty/serial/8250/8250_port.c:1833 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1819 [inline] serial8250_default_handle_irq+0xc0/0x150 drivers/tty/serial/8250/8250_port.c:1849 serial8250_interrupt+0xf1/0x1a0 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x15d/0x970 kernel/irq/handle.c:149 handle_irq_event_percpu+0x74/0x160 kernel/irq/handle.c:189 handle_irq_event+0xa7/0x134 kernel/irq/handle.c:206 handle_edge_irq+0x25e/0x8d0 kernel/irq/chip.c:830 generic_handle_irq_desc include/linux/irqdesc.h:156 [inline] do_IRQ+0xde/0x280 arch/x86/kernel/irq.c:250 ret_from_intr+0x0/0x36 native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:689 default_idle_call+0x84/0xb0 kernel/sched/idle.c:94 cpuidle_idle_call kernel/sched/idle.c:154 [inline] do_idle+0x3c8/0x6e0 kernel/sched/idle.c:269 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:361 rest_init+0x23b/0x371 init/main.c:655 arch_call_rest_init+0xe/0x1b start_kernel+0x886/0x8c5 init/main.c:994 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490 x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:471 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242 -> #1 (&port_lock_key){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:159 serial8250_console_write+0x253/0x9a0 drivers/tty/serial/8250/8250_port.c:3146 univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:586 call_console_drivers kernel/printk/printk.c:1789 [inline] console_unlock+0xadb/0xf10 kernel/printk/printk.c:2474 vprintk_emit+0x2a0/0x700 kernel/printk/printk.c:1994 vprintk_default+0x28/0x30 kernel/printk/printk.c:2021 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:386 printk+0xba/0xed kernel/printk/printk.c:2054 register_console kernel/printk/printk.c:2827 [inline] register_console+0x565/0x7f0 kernel/printk/printk.c:2706 univ8250_console_init+0x3e/0x4b drivers/tty/serial/8250/8250_core.c:681 console_init+0x461/0x67b kernel/printk/printk.c:2927 start_kernel+0x636/0x8c5 init/main.c:921 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490 x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:471 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242 -> #0 (console_owner){-.-.}: check_prev_add kernel/locking/lockdep.c:2481 [inline] check_prevs_add kernel/locking/lockdep.c:2586 [inline] validate_chain kernel/locking/lockdep.c:3203 [inline] __lock_acquire+0x29cd/0x6320 kernel/locking/lockdep.c:4190 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4720 console_trylock_spinning kernel/printk/printk.c:1746 [inline] vprintk_emit+0x43a/0x700 kernel/printk/printk.c:1993 vprintk_default+0x28/0x30 kernel/printk/printk.c:2021 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:386 printk+0xba/0xed kernel/printk/printk.c:2054 tty_port_close_start.part.0+0x52a/0x580 drivers/tty/tty_port.c:569 tty_port_close_start drivers/tty/tty_port.c:641 [inline] tty_port_close+0x4e/0x100 drivers/tty/tty_port.c:634 tpk_close+0x8e/0xa4 drivers/char/ttyprintk.c:110 tty_release+0x3ba/0xe90 drivers/tty/tty_io.c:1683 __fput+0x2ff/0x890 fs/file_table.c:280 ____fput+0x16/0x20 fs/file_table.c:313 task_work_run+0x145/0x1c0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x316/0x380 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+0x676/0x790 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.0/20047: #0: ffff88809f3b8198 (&tty->legacy_mutex){+.+.}, at: tty_lock+0xc7/0x130 drivers/tty/tty_mutex.c:19 #1: ffffffff8c374d40 (&(&port->lock)->rlock){-.-.}, at: tty_port_close_start.part.0+0x2b/0x580 drivers/tty/tty_port.c:567 stack backtrace: CPU: 1 PID: 20047 Comm: syz-executor.0 Not tainted 5.6.0-rc2-next-20200219-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+0x197/0x210 lib/dump_stack.c:118 print_circular_bug.isra.0.cold+0x163/0x172 kernel/locking/lockdep.c:1688 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1812 check_prev_add kernel/locking/lockdep.c:2481 [inline] check_prevs_add kernel/locking/lockdep.c:2586 [inline] validate_chain kernel/locking/lockdep.c:3203 [inline] __lock_acquire+0x29cd/0x6320 kernel/locking/lockdep.c:4190 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4720 console_trylock_spinning kernel/printk/printk.c:1746 [inline] vprintk_emit+0x43a/0x700 kernel/printk/printk.c:1993 vprintk_default+0x28/0x30 kernel/printk/printk.c:2021 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:386 printk+0xba/0xed kernel/printk/printk.c:2054 tty_port_close_start.part.0+0x52a/0x580 drivers/tty/tty_port.c:569 tty_port_close_start drivers/tty/tty_port.c:641 [inline] tty_port_close+0x4e/0x100 drivers/tty/tty_port.c:634 tpk_close+0x8e/0xa4 drivers/char/ttyprintk.c:110 tty_release+0x3ba/0xe90 drivers/tty/tty_io.c:1683 __fput+0x2ff/0x890 fs/file_table.c:280 ____fput+0x16/0x20 fs/file_table.c:313 task_work_run+0x145/0x1c0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x316/0x380 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+0x676/0x790 arch/x86/entry/common.c:304 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x415fe1 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:00007ffe50e58fc0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000415fe1 RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000770120 R09: 01ffffffffffffff R10: 00007ffe50e59090 R11: 0000000000000293 R12: 000000000076bf20 R13: 0000000000770128 R14: 0000000000000000 R15: 000000000076bf2c