ttyprintk ttyprintk: tty_port_close_start: tty->count = 1 port count = 3 ====================================================== WARNING: possible circular locking dependency detected 4.19.167-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.1/14133 is trying to acquire lock: 0000000001f36286 (console_owner){-.-.}, at: log_next kernel/printk/printk.c:511 [inline] 0000000001f36286 (console_owner){-.-.}, at: console_unlock+0x3a9/0x1110 kernel/printk/printk.c:2447 but task is already holding lock: 000000001d5b3b04 (&(&port->lock)->rlock){-.-.}, at: tty_port_close_start.part.0+0x28/0x540 drivers/tty/tty_port.c:574 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&(&port->lock)->rlock){-.-.}: tty_port_tty_get+0x1d/0x80 drivers/tty/tty_port.c:289 tty_port_default_wakeup+0x11/0x40 drivers/tty/tty_port.c:47 serial8250_tx_chars+0x490/0xaf0 drivers/tty/serial/8250/8250_port.c:1806 serial8250_handle_irq.part.0+0x31f/0x3d0 drivers/tty/serial/8250/8250_port.c:1893 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1866 [inline] serial8250_default_handle_irq+0xae/0x220 drivers/tty/serial/8250/8250_port.c:1909 serial8250_interrupt+0x101/0x240 drivers/tty/serial/8250/8250_core.c:125 __handle_irq_event_percpu+0x27e/0x8e0 kernel/irq/handle.c:149 handle_irq_event_percpu kernel/irq/handle.c:189 [inline] handle_irq_event+0x102/0x285 kernel/irq/handle.c:206 handle_edge_irq+0x260/0xcf0 kernel/irq/chip.c:797 generic_handle_irq_desc include/linux/irqdesc.h:155 [inline] handle_irq+0x35/0x50 arch/x86/kernel/irq_64.c:87 do_IRQ+0x93/0x1c0 arch/x86/kernel/irq.c:246 ret_from_intr+0x0/0x1e arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline] _raw_spin_unlock_irqrestore+0xa3/0xe0 kernel/locking/spinlock.c:184 spin_unlock_irqrestore include/linux/spinlock.h:384 [inline] uart_write+0x3bb/0x6f0 drivers/tty/serial/serial_core.c:612 do_output_char+0x5de/0x850 drivers/tty/n_tty.c:445 process_output drivers/tty/n_tty.c:512 [inline] n_tty_write+0x46e/0xff0 drivers/tty/n_tty.c:2343 do_tty_write drivers/tty/tty_io.c:960 [inline] tty_write+0x496/0x810 drivers/tty/tty_io.c:1044 redirected_tty_write+0xaa/0xb0 drivers/tty/tty_io.c:1065 do_loop_readv_writev fs/read_write.c:704 [inline] do_loop_readv_writev fs/read_write.c:688 [inline] do_iter_write+0x461/0x5d0 fs/read_write.c:962 vfs_writev+0x153/0x2e0 fs/read_write.c:1005 do_writev+0x136/0x330 fs/read_write.c:1040 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&port_lock_key){-.-.}: serial8250_console_write+0x89b/0xad0 drivers/tty/serial/8250/8250_port.c:3270 call_console_drivers kernel/printk/printk.c:1764 [inline] console_unlock+0xbb6/0x1110 kernel/printk/printk.c:2460 vprintk_emit+0x2d1/0x740 kernel/printk/printk.c:1965 vprintk_func+0x79/0x17e kernel/printk/printk_safe.c:397 printk+0xba/0xed kernel/printk/printk.c:2040 register_console+0x87f/0xc90 kernel/printk/printk.c:2776 univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:684 console_init+0x4cb/0x718 kernel/printk/printk.c:2862 start_kernel+0x686/0x911 init/main.c:659 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 -> #0 (console_owner){-.-.}: console_lock_spinning_enable kernel/printk/printk.c:1627 [inline] console_unlock+0x411/0x1110 kernel/printk/printk.c:2457 vprintk_emit+0x2d1/0x740 kernel/printk/printk.c:1965 vprintk_func+0x79/0x17e kernel/printk/printk_safe.c:397 printk+0xba/0xed kernel/printk/printk.c:2040 tty_port_close_start.part.0+0x4f3/0x540 drivers/tty/tty_port.c:576 tty_port_close_start drivers/tty/tty_port.c:648 [inline] tty_port_close+0x46/0x160 drivers/tty/tty_port.c:641 tty_release+0x45e/0x1210 drivers/tty/tty_io.c:1678 __fput+0x2ce/0x890 fs/file_table.c:278 task_work_run+0x148/0x1c0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:193 [inline] exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296 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-executor.1/14133: #0: 00000000828d9b52 (&tty->legacy_mutex){+.+.}, at: tty_lock+0x6a/0xa0 drivers/tty/tty_mutex.c:19 #1: 000000001d5b3b04 (&(&port->lock)->rlock){-.-.}, at: tty_port_close_start.part.0+0x28/0x540 drivers/tty/tty_port.c:574 #2: 0000000066eab7ad (console_lock){+.+.}, at: vprintk_func+0x79/0x17e kernel/printk/printk_safe.c:397 stack backtrace: CPU: 1 PID: 14133 Comm: syz-executor.1 Not tainted 4.19.167-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+0x1fc/0x2fe lib/dump_stack.c:118 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1221 check_prev_add kernel/locking/lockdep.c:1865 [inline] check_prevs_add kernel/locking/lockdep.c:1978 [inline] validate_chain kernel/locking/lockdep.c:2419 [inline] __lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3415 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3907 console_lock_spinning_enable kernel/printk/printk.c:1627 [inline] console_unlock+0x411/0x1110 kernel/printk/printk.c:2457 vprintk_emit+0x2d1/0x740 kernel/printk/printk.c:1965 vprintk_func+0x79/0x17e kernel/printk/printk_safe.c:397 printk+0xba/0xed kernel/printk/printk.c:2040 tty_port_close_start.part.0+0x4f3/0x540 drivers/tty/tty_port.c:576 tty_port_close_start drivers/tty/tty_port.c:648 [inline] tty_port_close+0x46/0x160 drivers/tty/tty_port.c:641 tty_release+0x45e/0x1210 drivers/tty/tty_io.c:1678 __fput+0x2ce/0x890 fs/file_table.c:278 task_work_run+0x148/0x1c0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:193 [inline] exit_to_usermode_loop+0x251/0x2a0 arch/x86/entry/common.c:167 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x538/0x620 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x417b71 Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 a4 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:00007ffdc0c90020 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000008 RCX: 0000000000417b71 RDX: 0000000000000000 RSI: 00007f7720276004 RDI: 0000000000000007 RBP: 0000000000000001 R08: 00000000000015bb R09: 000000001e9375bf R10: 00007ffdc0c90100 R11: 0000000000000293 R12: ffffffffffffffff R13: 00000000001ee693 R14: 00000000000003e8 R15: 000000000119c034 ip6_tunnel: ip6gretap0 xmit: Local address not yet configured!