============================================ WARNING: possible recursive locking detected 4.19.211-syzkaller #0 Not tainted -------------------------------------------- syz-executor.0/2564 is trying to acquire lock: 000000008464c7ee (&port_lock_key){-.-.}, at: uart_write+0x1ce/0x6f0 drivers/tty/serial/serial_core.c:591 but task is already holding lock: 000000008464c7ee (&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 5 locks held by syz-executor.0/2564: #0: 00000000551391ad (&sig->cred_guard_mutex){+.+.}, at: __do_sys_perf_event_open kernel/events/core.c:10640 [inline] #0: 00000000551391ad (&sig->cred_guard_mutex){+.+.}, at: __se_sys_perf_event_open+0x18eb/0x2720 kernel/events/core.c:10549 #1: 0000000079adf16c (&ctx->mutex){+.+.}, at: __do_sys_perf_event_open kernel/events/core.c:10822 [inline] #1: 0000000079adf16c (&ctx->mutex){+.+.}, at: __se_sys_perf_event_open+0xaf7/0x2720 kernel/events/core.c:10549 #2: 00000000d67703b0 (&(&i->lock)->rlock){-.-.}, at: spin_lock include/linux/spinlock.h:329 [inline] #2: 00000000d67703b0 (&(&i->lock)->rlock){-.-.}, at: serial8250_interrupt+0x3a/0x240 drivers/tty/serial/8250/8250_core.c:115 #3: 000000008464c7ee (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1876 #4: 000000005fcfea21 (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:293 stack backtrace: CPU: 1 PID: 2564 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:arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline] RIP: 0010:generic_exec_single+0x317/0x490 kernel/smp.c:154 Code: 00 fc ff df 48 c1 e8 03 80 3c 10 00 0f 85 5a 01 00 00 48 83 3d 61 04 99 08 00 0f 84 db 00 00 00 e8 3e 07 0a 00 48 89 df 57 9d <0f> 1f 44 00 00 45 31 e4 e9 39 fe ff ff e8 27 07 0a 00 0f 0b e9 3a RSP: 0018:ffff888050bc7b08 EFLAGS: 00000293 ORIG_RAX: ffffffffffffffd2 RAX: ffff888053e1e680 RBX: 0000000000000293 RCX: 1ffff1100a7c3dea RDX: 0000000000000000 RSI: ffffffff81587e32 RDI: 0000000000000293 RBP: 0000000000000200 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff888050bc7b80 R13: ffff888050bc7c40 R14: ffffffff81767200 R15: ffff888053e1e6bc smp_call_function_single+0x1cf/0x420 kernel/smp.c:299 task_function_call+0xe0/0x170 kernel/events/core.c:115 perf_install_in_context+0x238/0x3c0 kernel/events/core.c:2623 __do_sys_perf_event_open kernel/events/core.c:10924 [inline] __se_sys_perf_event_open+0xe5d/0x2720 kernel/events/core.c:10549 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7f6e330a8409 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:00007f6e31a1d168 EFLAGS: 00000246 ORIG_RAX: 000000000000012a RAX: ffffffffffffffda RBX: 00007f6e331baf80 RCX: 00007f6e330a8409 RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000000020000480 RBP: 00007f6e33103367 R08: 0000000000000000 R09: 0000000000000000 R10: ffffffffffffffff R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffee48c7fef R14: 00007f6e31a1d300 R15: 0000000000022000 ---------------- Code disassembly (best guess), 3 bytes skipped: 0: df 48 c1 fisttps -0x3f(%rax) 3: e8 03 80 3c 10 callq 0x103c800b 8: 00 0f add %cl,(%rdi) a: 85 5a 01 test %ebx,0x1(%rdx) d: 00 00 add %al,(%rax) f: 48 83 3d 61 04 99 08 cmpq $0x0,0x8990461(%rip) # 0x8990478 16: 00 17: 0f 84 db 00 00 00 je 0xf8 1d: e8 3e 07 0a 00 callq 0xa0760 22: 48 89 df mov %rbx,%rdi 25: 57 push %rdi 26: 9d popfq * 27: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) <-- trapping instruction 2c: 45 31 e4 xor %r12d,%r12d 2f: e9 39 fe ff ff jmpq 0xfffffe6d 34: e8 27 07 0a 00 callq 0xa0760 39: 0f 0b ud2 3b: e9 .byte 0xe9 3c: 3a .byte 0x3a