============================================ WARNING: possible recursive locking detected 4.14.285-syzkaller #0 Not tainted -------------------------------------------- syz-executor.0/10392 is trying to acquire lock: (&port_lock_key){-.-.}, at: [] uart_write+0x109/0x560 drivers/tty/serial/serial_core.c:611 but task is already holding lock: (&port_lock_key){-.-.}, at: [] serial8250_handle_irq.part.0+0x20/0x330 drivers/tty/serial/8250/8250_port.c:1891 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.0/10392: #0: (&(&i->lock)->rlock){-.-.}, at: [] spin_lock include/linux/spinlock.h:317 [inline] #0: (&(&i->lock)->rlock){-.-.}, at: [] serial8250_interrupt+0x3a/0x210 drivers/tty/serial/8250/8250_core.c:119 #1: (&port_lock_key){-.-.}, at: [] serial8250_handle_irq.part.0+0x20/0x330 drivers/tty/serial/8250/8250_port.c:1891 #2: (&tty->ldisc_sem){++++}, at: [] tty_ldisc_ref+0x1b/0x80 drivers/tty/tty_ldisc.c:305 stack backtrace: CPU: 1 PID: 10392 Comm: syz-executor.0 Not tainted 4.14.285-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x1b2/0x281 lib/dump_stack.c:58 print_deadlock_bug kernel/locking/lockdep.c:1800 [inline] check_deadlock kernel/locking/lockdep.c:1847 [inline] validate_chain kernel/locking/lockdep.c:2448 [inline] __lock_acquire.cold+0x180/0x97c kernel/locking/lockdep.c:3491 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x8c/0xc0 kernel/locking/spinlock.c:160 uart_write+0x109/0x560 drivers/tty/serial/serial_core.c:611 n_hdlc_send_frames+0x241/0x410 drivers/tty/n_hdlc.c:404 n_hdlc_tty_wakeup+0x95/0xb0 drivers/tty/n_hdlc.c:480 tty_wakeup+0xc3/0xf0 drivers/tty/tty_io.c:533 tty_port_default_wakeup+0x26/0x40 drivers/tty/tty_port.c:49 serial8250_tx_chars+0x3fe/0xc70 drivers/tty/serial/8250/8250_port.c:1828 serial8250_handle_irq.part.0+0x28d/0x330 drivers/tty/serial/8250/8250_port.c:1915 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1888 [inline] serial8250_default_handle_irq+0x8a/0x1f0 drivers/tty/serial/8250/8250_port.c:1931 serial8250_interrupt+0xf3/0x210 drivers/tty/serial/8250/8250_core.c:129 __handle_irq_event_percpu+0xee/0x7f0 kernel/irq/handle.c:147 handle_irq_event_percpu kernel/irq/handle.c:187 [inline] handle_irq_event+0xed/0x240 kernel/irq/handle.c:204 handle_edge_irq+0x224/0xc40 kernel/irq/chip.c:770 generic_handle_irq_desc include/linux/irqdesc.h:159 [inline] handle_irq+0x35/0x50 arch/x86/kernel/irq_64.c:87 do_IRQ+0x93/0x1d0 arch/x86/kernel/irq.c:230 common_interrupt+0x93/0x93 arch/x86/entry/entry_64.S:576 RIP: 0010:arch_local_save_flags arch/x86/include/asm/paravirt.h:774 [inline] RIP: 0010:arch_local_irq_save arch/x86/include/asm/paravirt.h:796 [inline] RIP: 0010:lock_is_held_type+0x6c/0x210 kernel/locking/lockdep.c:4032 RSP: 0018:ffff888092937970 EFLAGS: 00000246 ORIG_RAX: ffffffffffffffc8 RAX: 1ffffffff11e1340 RBX: ffff8880916ce200 RCX: 0000000000000001 RDX: dffffc0000000000 RSI: 00000000ffffffff RDI: ffff8880916cea84 RBP: ffffffff88f780c0 R08: 000000000000da1a R09: 0000000000000000 R10: 0000000000000000 R11: ffff8880916ce200 R12: 000000000000000a R13: ffff888092937a40 R14: ffff888092937b38 R15: dffffc0000000000 lock_is_held include/linux/lockdep.h:437 [inline] ___might_sleep+0x1ea/0x2b0 kernel/sched/core.c:6006 __might_fault+0x9f/0x1b0 mm/memory.c:4697 _copy_from_user+0x27/0x100 lib/usercopy.c:10 copy_from_user include/linux/uaccess.h:147 [inline] copy_msghdr_from_user+0x7b/0x3b0 net/socket.c:1943 ___sys_recvmsg+0xe5/0x4d0 net/socket.c:2209 __sys_recvmmsg+0x1f3/0x5d0 net/socket.c:2329 SYSC_recvmmsg net/socket.c:2405 [inline] SyS_recvmmsg+0x125/0x140 net/socket.c:2394 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x7fa80f9eb109 RSP: 002b:00007fa80e33f168 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00007fa80fafe030 RCX: 00007fa80f9eb109 RDX: 0000000000010106 RSI: 00000000200000c0 RDI: 0000000000000003 RBP: 00007fa80fa4505d R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fff9df9a52f R14: 00007fa80e33f300 R15: 0000000000022000