============================================ WARNING: possible recursive locking detected 4.19.211-syzkaller #0 Not tainted -------------------------------------------- systemd-udevd/4700 is trying to acquire lock: 00000000c8f79c24 (&port_lock_key){-.-.}, at: uart_write+0x1ce/0x6f0 drivers/tty/serial/serial_core.c:591 but task is already holding lock: 00000000c8f79c24 (&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 systemd-udevd/4700: #0: 000000007c7eb73f (&(&i->lock)->rlock){-.-.}, at: spin_lock include/linux/spinlock.h:329 [inline] #0: 000000007c7eb73f (&(&i->lock)->rlock){-.-.}, at: serial8250_interrupt+0x3a/0x240 drivers/tty/serial/8250/8250_core.c:115 #1: 00000000c8f79c24 (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1876 #2: 0000000065b4dc53 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:293 stack backtrace: CPU: 1 PID: 4700 Comm: systemd-udevd Not tainted 4.19.211-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 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:__call_rcu.constprop.0+0x278/0x7f0 kernel/rcu/tree.c:3031 Code: 00 00 00 00 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 8d 04 00 00 48 83 3d 2c f3 9f 08 00 0f 84 dc 02 00 00 48 8b 3c 24 57 9d <0f> 1f 44 00 00 48 83 c4 20 5b 5d 41 5c 41 5d 41 5e 41 5f c3 80 3d RSP: 0018:ffff88809ad57a50 EFLAGS: 00000286 ORIG_RAX: ffffffffffffffd5 RAX: 1ffffffff13e3051 RBX: ffff8880447f2870 RCX: 0000000000000000 RDX: dffffc0000000000 RSI: 0000000000000001 RDI: 0000000000000286 RBP: ffff8880ba12bf10 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff89f88280 R13: ffff8880ba12be80 R14: ffff8880ba12bf00 R15: ffff8880ba12beb8 dentry_free+0xbf/0x150 fs/dcache.c:350 __dentry_kill+0x4c6/0x640 fs/dcache.c:580 dentry_kill+0xc4/0x510 fs/dcache.c:685 dput+0x55f/0x640 fs/dcache.c:846 path_put fs/namei.c:484 [inline] terminate_walk+0x2c4/0x5c0 fs/namei.c:598 path_lookupat+0x356/0x8d0 fs/namei.c:2333 filename_lookup+0x1ac/0x5a0 fs/namei.c:2349 user_path_at include/linux/namei.h:57 [inline] do_faccessat+0x248/0x7a0 fs/open.c:397 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f1bae0bd9c7 Code: 83 c4 08 48 3d 01 f0 ff ff 73 01 c3 48 8b 0d c8 d4 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 b8 15 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d a1 d4 2b 00 f7 d8 64 89 01 48 RSP: 002b:00007fff84fd94a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000015 RAX: ffffffffffffffda RBX: 0000561fdc0373b0 RCX: 00007f1bae0bd9c7 RDX: 00746e657665752f RSI: 0000000000000000 RDI: 00007fff84fd94b0 RBP: 00007fff84fd9520 R08: 0000000000004c40 R09: 0000000000001010 R10: 00007f1bae37bb58 R11: 0000000000000246 R12: 0000561fdaac2856 R13: 0000561fdc012d60 R14: 00007fff84fd94b0 R15: 0000561fdc021ab0 ---------------- Code disassembly (best guess), 7 bytes skipped: 0: df 48 c1 fisttps -0x3f(%rax) 3: e8 03 80 3c 10 callq 0x103c800b 8: 00 0f add %cl,(%rdi) a: 85 8d 04 00 00 48 test %ecx,0x48000004(%rbp) 10: 83 3d 2c f3 9f 08 00 cmpl $0x0,0x89ff32c(%rip) # 0x89ff343 17: 0f 84 dc 02 00 00 je 0x2f9 1d: 48 8b 3c 24 mov (%rsp),%rdi 21: 57 push %rdi 22: 9d popfq * 23: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) <-- trapping instruction 28: 48 83 c4 20 add $0x20,%rsp 2c: 5b pop %rbx 2d: 5d pop %rbp 2e: 41 5c pop %r12 30: 41 5d pop %r13 32: 41 5e pop %r14 34: 41 5f pop %r15 36: c3 retq 37: 80 .byte 0x80 38: 3d .byte 0x3d