============================================ WARNING: possible recursive locking detected 4.19.211-syzkaller #0 Not tainted -------------------------------------------- syz-executor.5/8118 is trying to acquire lock: 00000000476bfb19 (&port_lock_key){-.-.}, at: uart_write+0x1ce/0x6f0 drivers/tty/serial/serial_core.c:591 but task is already holding lock: 00000000476bfb19 (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1876 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&port_lock_key); lock(&port_lock_key); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by syz-executor.5/8118: #0: 00000000ca24755e (&(&i->lock)->rlock){-.-.}, at: spin_lock include/linux/spinlock.h:329 [inline] #0: 00000000ca24755e (&(&i->lock)->rlock){-.-.}, at: serial8250_interrupt+0x3a/0x240 drivers/tty/serial/8250/8250_core.c:115 #1: 00000000476bfb19 (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1876 #2: 000000002a893f9e (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:293 stack backtrace: CPU: 1 PID: 8118 Comm: syz-executor.5 Not tainted 4.19.211-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1fc/0x2ef lib/dump_stack.c:118 print_deadlock_bug kernel/locking/lockdep.c:1764 [inline] check_deadlock kernel/locking/lockdep.c:1808 [inline] validate_chain kernel/locking/lockdep.c:2404 [inline] __lock_acquire.cold+0x121/0x57e kernel/locking/lockdep.c:3416 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x8c/0xc0 kernel/locking/spinlock.c:152 uart_write+0x1ce/0x6f0 drivers/tty/serial/serial_core.c:591 n_hdlc_send_frames+0x278/0x470 drivers/tty/n_hdlc.c:403 n_hdlc_tty_wakeup+0xa0/0xc0 drivers/tty/n_hdlc.c:479 tty_wakeup+0xd4/0x110 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0x26/0x40 drivers/tty/tty_port.c:50 serial8250_tx_chars+0x490/0xaf0 drivers/tty/serial/8250/8250_port.c:1813 serial8250_handle_irq.part.0+0x31f/0x3d0 drivers/tty/serial/8250/8250_port.c:1900 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1873 [inline] serial8250_default_handle_irq+0xae/0x220 drivers/tty/serial/8250/8250_port.c:1916 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+0x102/0x290 kernel/irq/handle.c:206 handle_edge_irq+0x260/0xcf0 kernel/irq/chip.c:800 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 common_interrupt+0xf/0xf arch/x86/entry/entry_64.S:670 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline] RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline] RIP: 0010:_raw_spin_unlock_irqrestore+0xa3/0xe0 kernel/locking/spinlock.c:184 Code: 48 c7 c0 88 82 f1 89 48 ba 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 75 2f 48 83 3d 7c 31 d8 01 00 74 15 48 89 df 57 9d <0f> 1f 44 00 00 eb b2 e8 fb eb e6 f8 eb c0 0f 0b 0f 0b 48 c7 c7 88 RSP: 0018:ffff8880b0207c18 EFLAGS: 00000286 ORIG_RAX: ffffffffffffffd2 RAX: 1ffffffff13e3051 RBX: 0000000000000286 RCX: 0000000000000000 RDX: dffffc0000000000 RSI: 0000000000000001 RDI: 0000000000000286 RBP: ffff8880a449e820 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880b0207d00 R13: 0000000000000004 R14: 00007ffe80d14aac R15: 0000000000000000 do_wait+0x184/0x9c0 kernel/exit.c:1496 kernel_wait4+0x14c/0x260 kernel/exit.c:1655 __do_sys_wait4 kernel/exit.c:1667 [inline] __se_sys_wait4+0x149/0x160 kernel/exit.c:1663 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f12e5489cd7 Code: 89 7c 24 10 48 89 4c 24 18 e8 f5 58 02 00 4c 8b 54 24 18 8b 54 24 14 41 89 c0 48 8b 74 24 08 8b 7c 24 10 b8 3d 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 89 44 24 10 e8 25 59 02 00 8b 44 RSP: 002b:00007ffe80d14a20 EFLAGS: 00000293 ORIG_RAX: 000000000000003d RAX: ffffffffffffffda RBX: 0000000000001786 RCX: 00007f12e5489cd7 RDX: 0000000040000001 RSI: 00007ffe80d14aac RDI: 00000000ffffffff RBP: 00007ffe80d14aac R08: 0000000000000000 R09: 000001746031ee5a R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000032 R13: 000000000016213d R14: 0000000000000002 R15: 00007ffe80d14b10 ---------------- Code disassembly (best guess): 0: 48 c7 c0 88 82 f1 89 mov $0xffffffff89f18288,%rax 7: 48 ba 00 00 00 00 00 movabs $0xdffffc0000000000,%rdx e: fc ff df 11: 48 c1 e8 03 shr $0x3,%rax 15: 80 3c 10 00 cmpb $0x0,(%rax,%rdx,1) 19: 75 2f jne 0x4a 1b: 48 83 3d 7c 31 d8 01 cmpq $0x0,0x1d8317c(%rip) # 0x1d8319f 22: 00 23: 74 15 je 0x3a 25: 48 89 df mov %rbx,%rdi 28: 57 push %rdi 29: 9d popfq * 2a: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) <-- trapping instruction 2f: eb b2 jmp 0xffffffe3 31: e8 fb eb e6 f8 callq 0xf8e6ec31 36: eb c0 jmp 0xfffffff8 38: 0f 0b ud2 3a: 0f 0b ud2 3c: 48 rex.W 3d: c7 .byte 0xc7 3e: c7 (bad) 3f: 88 .byte 0x88