============================================ WARNING: possible recursive locking detected 4.19.211-syzkaller #0 Not tainted -------------------------------------------- syz-executor.3/27248 is trying to acquire lock: 00000000bccc266b (&port_lock_key){-.-.}, at: uart_write+0x1ce/0x6f0 drivers/tty/serial/serial_core.c:591 but task is already holding lock: 00000000bccc266b (&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.3/27248: #0: 00000000a90edefa (&(&i->lock)->rlock){-.-.}, at: spin_lock include/linux/spinlock.h:329 [inline] #0: 00000000a90edefa (&(&i->lock)->rlock){-.-.}, at: serial8250_interrupt+0x3a/0x240 drivers/tty/serial/8250/8250_core.c:115 #1: 00000000bccc266b (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1876 #2: 0000000079ce1472 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:293 stack backtrace: CPU: 1 PID: 27248 Comm: syz-executor.3 Not tainted 4.19.211-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022 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:finish_task_switch+0x16b/0x760 kernel/sched/core.c:2680 Code: e8 9a ea d7 06 48 b8 00 00 00 00 00 fc ff df 65 48 8b 1c 25 c0 df 01 00 48 8d bb 60 13 00 00 48 89 fa 48 c1 ea 03 0f b6 04 02 <5a> 84 c0 74 08 3c 03 0f 8e e8 03 00 00 81 a3 60 13 00 00 ff ff ff RSP: 0018:ffff8880479a7598 EFLAGS: 00000a02 ORIG_RAX: ffffffffffffffd5 RAX: 0000000000000000 RBX: ffff88809bd3e400 RCX: 0000000000000000 RDX: 1ffff110137a7eec RSI: 0000000000000001 RDI: ffff88809bd3f760 RBP: ffff8880479a75e0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880ba12b0c0 R13: ffff888045afc2c0 R14: 0000000000000000 R15: 0000000000000000 context_switch kernel/sched/core.c:2831 [inline] __schedule+0x88f/0x2040 kernel/sched/core.c:3517 schedule+0x8d/0x1b0 kernel/sched/core.c:3561 schedule_timeout+0x92d/0xfe0 kernel/time/timer.c:1794 unix_wait_for_peer+0x237/0x270 net/unix/af_unix.c:1240 unix_dgram_sendmsg+0x10e5/0x12c0 net/unix/af_unix.c:1811 sock_sendmsg_nosec net/socket.c:651 [inline] sock_sendmsg+0xc3/0x120 net/socket.c:661 ___sys_sendmsg+0x3b3/0x8e0 net/socket.c:2227 __sys_sendmmsg+0x195/0x470 net/socket.c:2322 __do_sys_sendmmsg net/socket.c:2351 [inline] __se_sys_sendmmsg net/socket.c:2348 [inline] __x64_sys_sendmmsg+0x99/0x100 net/socket.c:2348 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f694f11c5a9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f694da90168 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007f694f23df80 RCX: 00007f694f11c5a9 RDX: 0000000000000318 RSI: 00000000200bd000 RDI: 0000000000000004 RBP: 00007f694f177580 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffcff14154f R14: 00007f694da90300 R15: 0000000000022000 ---------------- Code disassembly (best guess): 0: e8 9a ea d7 06 callq 0x6d7ea9f 5: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax c: fc ff df f: 65 48 8b 1c 25 c0 df mov %gs:0x1dfc0,%rbx 16: 01 00 18: 48 8d bb 60 13 00 00 lea 0x1360(%rbx),%rdi 1f: 48 89 fa mov %rdi,%rdx 22: 48 c1 ea 03 shr $0x3,%rdx 26: 0f b6 04 02 movzbl (%rdx,%rax,1),%eax * 2a: 5a pop %rdx <-- trapping instruction 2b: 84 c0 test %al,%al 2d: 74 08 je 0x37 2f: 3c 03 cmp $0x3,%al 31: 0f 8e e8 03 00 00 jle 0x41f 37: 81 .byte 0x81 38: a3 .byte 0xa3 39: 60 (bad) 3a: 13 00 adc (%rax),%eax 3c: 00 ff add %bh,%bh 3e: ff (bad) 3f: ff .byte 0xff