============================================ WARNING: possible recursive locking detected 5.15.0-rc7-syzkaller #0 Not tainted -------------------------------------------- systemd-udevd/22480 is trying to acquire lock: ffffffff905196f0 (&port_lock_key){-.-.}-{2:2}, at: uart_write+0x12c/0x570 drivers/tty/serial/serial_core.c:570 but task is already holding lock: ffffffff905196f0 (&port_lock_key){-.-.}-{2:2}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1908 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 4 locks held by systemd-udevd/22480: #0: ffffffff8b981b20 (rcu_read_lock){....}-{1:2}, at: path_init+0x699/0x1920 fs/namei.c:2329 #1: ffff888019d7e030 (&i->lock){-.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #1: ffff888019d7e030 (&i->lock){-.-.}-{2:2}, at: serial8250_interrupt+0x3a/0x200 drivers/tty/serial/8250/8250_core.c:116 #2: ffffffff905196f0 (&port_lock_key){-.-.}-{2:2}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1908 #3: ffff88803ec8b098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:273 stack backtrace: CPU: 0 PID: 22480 Comm: systemd-udevd Not tainted 5.15.0-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:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 print_deadlock_bug kernel/locking/lockdep.c:2944 [inline] check_deadlock kernel/locking/lockdep.c:2987 [inline] validate_chain kernel/locking/lockdep.c:3776 [inline] __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5015 lock_acquire kernel/locking/lockdep.c:5625 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:162 uart_write+0x12c/0x570 drivers/tty/serial/serial_core.c:570 n_hdlc_send_frames+0x24b/0x490 drivers/tty/n_hdlc.c:290 tty_wakeup+0xe1/0x120 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0x26/0x40 drivers/tty/tty_port.c:51 serial8250_tx_chars+0x4f3/0xad0 drivers/tty/serial/8250/8250_port.c:1845 serial8250_handle_irq.part.0+0x328/0x3d0 drivers/tty/serial/8250/8250_port.c:1932 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1905 [inline] serial8250_default_handle_irq+0xb2/0x220 drivers/tty/serial/8250/8250_port.c:1949 serial8250_interrupt+0xfd/0x200 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x303/0x8f0 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0x102/0x280 kernel/irq/handle.c:213 handle_edge_irq+0x25f/0xd00 kernel/irq/chip.c:822 generic_handle_irq_desc include/linux/irqdesc.h:158 [inline] handle_irq arch/x86/kernel/irq.c:231 [inline] __common_interrupt+0x9d/0x210 arch/x86/kernel/irq.c:250 common_interrupt+0x9f/0xd0 arch/x86/kernel/irq.c:240 asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:629 RIP: 0010:mnt_user_ns include/linux/mount.h:81 [inline] RIP: 0010:link_path_walk.part.0+0x207/0xd00 fs/namei.c:2238 Code: 48 8b 44 24 38 80 38 00 0f 85 ac 09 00 00 48 be 00 00 00 00 00 fc ff df 49 8b 1e 48 8d 7b 18 48 89 f8 48 c1 e8 03 80 3c 30 00 <0f> 85 97 09 00 00 48 8b 43 18 48 89 44 24 10 48 8b 44 24 40 0f b6 RSP: 0018:ffffc9000a1d7b08 EFLAGS: 00000246 RAX: 1ffff11002a7c2d7 RBX: ffff8880153e16a0 RCX: 0000000000000000 RDX: ffff888086c51c80 RSI: dffffc0000000000 RDI: ffff8880153e16b8 RBP: dffffc0000000000 R08: fffffffffffff000 R09: 0000000000000073 R10: ffffffff81cd2f87 R11: 0000000000000000 R12: ffffc9000a1d7c90 R13: ffff888019af9120 R14: ffffc9000a1d7c90 R15: ffff888019af9121 link_path_walk fs/namei.c:2221 [inline] path_lookupat+0xc8/0x860 fs/namei.c:2448 filename_lookup+0x1c6/0x590 fs/namei.c:2478 user_path_at_empty+0x42/0x60 fs/namei.c:2801 do_readlinkat+0xcd/0x2f0 fs/stat.c:443 __do_sys_readlinkat fs/stat.c:470 [inline] __se_sys_readlinkat fs/stat.c:467 [inline] __x64_sys_readlinkat+0x93/0xf0 fs/stat.c:467 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7ff7006370ba Code: 48 8b 0d e1 bd 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 0b 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d ae bd 2b 00 f7 d8 64 89 01 48 RSP: 002b:00007fff371e7a98 EFLAGS: 00000206 ORIG_RAX: 000000000000010b RAX: ffffffffffffffda RBX: 000056469f41a130 RCX: 00007ff7006370ba RDX: 000056469f41a130 RSI: 000056469f4181e0 RDI: 00000000ffffff9c RBP: 0000000000000064 R08: 00007ff7008f3bd8 R09: 0000000000000070 R10: 0000000000000063 R11: 0000000000000206 R12: 000056469f4181e0 R13: 00000000ffffff9c R14: 00007fff371e7af0 R15: 0000000000000063 ---------------- Code disassembly (best guess): 0: 48 8b 44 24 38 mov 0x38(%rsp),%rax 5: 80 38 00 cmpb $0x0,(%rax) 8: 0f 85 ac 09 00 00 jne 0x9ba e: 48 be 00 00 00 00 00 movabs $0xdffffc0000000000,%rsi 15: fc ff df 18: 49 8b 1e mov (%r14),%rbx 1b: 48 8d 7b 18 lea 0x18(%rbx),%rdi 1f: 48 89 f8 mov %rdi,%rax 22: 48 c1 e8 03 shr $0x3,%rax 26: 80 3c 30 00 cmpb $0x0,(%rax,%rsi,1) * 2a: 0f 85 97 09 00 00 jne 0x9c7 <-- trapping instruction 30: 48 8b 43 18 mov 0x18(%rbx),%rax 34: 48 89 44 24 10 mov %rax,0x10(%rsp) 39: 48 8b 44 24 40 mov 0x40(%rsp),%rax 3e: 0f .byte 0xf 3f: b6 .byte 0xb6