============================================ WARNING: possible recursive locking detected 4.19.211-syzkaller #0 Not tainted -------------------------------------------- syz-executor.0/10184 is trying to acquire lock: 00000000ad8e0306 (&port_lock_key){-.-.}, at: uart_write+0x1ce/0x6f0 drivers/tty/serial/serial_core.c:591 but task is already holding lock: 00000000ad8e0306 (&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 4 locks held by syz-executor.0/10184: #0: 000000008641455f (rcu_read_lock){....}, at: is_bpf_text_address+0x0/0x1b0 kernel/bpf/core.c:533 #1: 00000000fd5bacbd (&(&i->lock)->rlock){-.-.}, at: spin_lock include/linux/spinlock.h:329 [inline] #1: 00000000fd5bacbd (&(&i->lock)->rlock){-.-.}, at: serial8250_interrupt+0x3a/0x240 drivers/tty/serial/8250/8250_core.c:115 #2: 00000000ad8e0306 (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1876 #3: 00000000f86c1f12 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:293 stack backtrace: CPU: 0 PID: 10184 Comm: syz-executor.0 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:__rcu_read_unlock+0x27/0x160 kernel/rcu/tree_plugin.h:421 Code: 00 00 00 48 b8 00 00 00 00 00 fc ff df 55 53 65 48 8b 1c 25 c0 df 01 00 48 8d ab 70 03 00 00 48 89 ea 48 c1 ea 03 0f b6 04 02 <84> c0 74 08 3c 03 0f 8e e5 00 00 00 8b 83 70 03 00 00 83 f8 01 74 RSP: 0018:ffff8880aaecf9a0 EFLAGS: 00000a02 ORIG_RAX: ffffffffffffffdb RAX: 0000000000000000 RBX: ffff8880a99d8200 RCX: ffffc90005c34000 RDX: 1ffff1101533b0ae RSI: ffffffff816d117a RDI: 0000000000000001 RBP: ffff8880a99d8570 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000074071 R12: 0000000000000000 R13: 0000000000000000 R14: ffff8880b2838940 R15: 0000000000000120 rcu_read_unlock include/linux/rcupdate.h:680 [inline] is_bpf_text_address+0xdf/0x1b0 kernel/bpf/core.c:548 kernel_text_address kernel/extable.c:152 [inline] kernel_text_address+0xbd/0xf0 kernel/extable.c:122 __kernel_text_address+0x9/0x30 kernel/extable.c:107 unwind_get_return_address arch/x86/kernel/unwind_orc.c:297 [inline] unwind_get_return_address+0x51/0x90 arch/x86/kernel/unwind_orc.c:292 __save_stack_trace+0xaf/0x190 arch/x86/kernel/stacktrace.c:45 save_stack mm/kasan/kasan.c:448 [inline] set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:553 kmem_cache_alloc+0x122/0x370 mm/slab.c:3559 kmem_cache_zalloc include/linux/slab.h:699 [inline] alloc_posix_timer kernel/time/posix-timers.c:453 [inline] do_timer_create+0x150/0x1420 kernel/time/posix-timers.c:506 __do_sys_timer_create kernel/time/posix-timers.c:583 [inline] __se_sys_timer_create kernel/time/posix-timers.c:572 [inline] __x64_sys_timer_create+0x186/0x1b0 kernel/time/posix-timers.c:572 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7faf0b542279 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:00007faf09eb7168 EFLAGS: 00000246 ORIG_RAX: 00000000000000de RAX: ffffffffffffffda RBX: 00007faf0b654f80 RCX: 00007faf0b542279 RDX: 0000000020000140 RSI: 0000000000000000 RDI: 0000000000000002 RBP: 00007faf0b59c2e9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffec069299f R14: 00007faf09eb7300 R15: 0000000000022000 ---------------- Code disassembly (best guess), 1 bytes skipped: 0: 00 00 add %al,(%rax) 2: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 9: fc ff df c: 55 push %rbp d: 53 push %rbx e: 65 48 8b 1c 25 c0 df mov %gs:0x1dfc0,%rbx 15: 01 00 17: 48 8d ab 70 03 00 00 lea 0x370(%rbx),%rbp 1e: 48 89 ea mov %rbp,%rdx 21: 48 c1 ea 03 shr $0x3,%rdx 25: 0f b6 04 02 movzbl (%rdx,%rax,1),%eax * 29: 84 c0 test %al,%al <-- trapping instruction 2b: 74 08 je 0x35 2d: 3c 03 cmp $0x3,%al 2f: 0f 8e e5 00 00 00 jle 0x11a 35: 8b 83 70 03 00 00 mov 0x370(%rbx),%eax 3b: 83 f8 01 cmp $0x1,%eax 3e: 74 .byte 0x74