============================================ WARNING: possible recursive locking detected 4.19.211-syzkaller #0 Not tainted -------------------------------------------- syz-executor.2/20436 is trying to acquire lock: 000000001d35ca13 (&port_lock_key){-.-.}, at: uart_write+0x1ce/0x6f0 drivers/tty/serial/serial_core.c:591 but task is already holding lock: 000000001d35ca13 (&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.2/20436: #0: 00000000e85f4e3b (&(&i->lock)->rlock){-.-.}, at: spin_lock include/linux/spinlock.h:329 [inline] #0: 00000000e85f4e3b (&(&i->lock)->rlock){-.-.}, at: serial8250_interrupt+0x3a/0x240 drivers/tty/serial/8250/8250_core.c:115 #1: 000000001d35ca13 (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1876 #2: 00000000455e006d (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:293 stack backtrace: CPU: 1 PID: 20436 Comm: syz-executor.2 Not tainted 4.19.211-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022 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:sock_rcvtimeo include/net/sock.h:2270 [inline] RIP: 0010:unix_dgram_recvmsg+0x7e9/0xdb0 net/unix/af_unix.c:2139 Code: 5c 41 5d 41 5e 41 5f c3 e8 84 38 62 fa 49 8d bc 24 f8 03 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 <0f> 85 aa 05 00 00 49 8b ac 24 f8 03 00 00 e9 16 f9 ff ff e8 4f 38 RSP: 0018:ffff8880afb778b0 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffd2 RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc9000d3b2000 RDX: 1ffff110136af387 RSI: ffffffff87004cec RDI: ffff88809b579c38 RBP: 0000000000000000 R08: ffff8880afb77b10 R09: 0000000000000000 R10: 0000000000000005 R11: 0000000000000000 R12: ffff88809b579840 R13: 00000000ffffffa1 R14: ffff88805458a900 R15: 0000000000000002 ___sys_recvmsg+0x255/0x570 net/socket.c:2389 __sys_recvmmsg+0x254/0x6d0 net/socket.c:2501 do_sys_recvmmsg+0x172/0x190 net/socket.c:2577 __do_sys_recvmmsg net/socket.c:2595 [inline] __se_sys_recvmmsg net/socket.c:2591 [inline] __x64_sys_recvmmsg+0xba/0x150 net/socket.c:2591 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7ff9c2107669 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:00007ff9c0a5a168 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00007ff9c2229050 RCX: 00007ff9c2107669 RDX: 0000000000010106 RSI: 00000000200000c0 RDI: 0000000000000003 RBP: 00007ff9c2162560 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffef9e5792f R14: 00007ff9c0a5a300 R15: 0000000000022000 ---------------- Code disassembly (best guess): 0: 5c pop %rsp 1: 41 5d pop %r13 3: 41 5e pop %r14 5: 41 5f pop %r15 7: c3 retq 8: e8 84 38 62 fa callq 0xfa623891 d: 49 8d bc 24 f8 03 00 lea 0x3f8(%r12),%rdi 14: 00 15: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 1c: fc ff df 1f: 48 89 fa mov %rdi,%rdx 22: 48 c1 ea 03 shr $0x3,%rdx 26: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) * 2a: 0f 85 aa 05 00 00 jne 0x5da <-- trapping instruction 30: 49 8b ac 24 f8 03 00 mov 0x3f8(%r12),%rbp 37: 00 38: e9 16 f9 ff ff jmpq 0xfffff953 3d: e8 .byte 0xe8 3e: 4f rex.WRXB 3f: 38 .byte 0x38