============================================ WARNING: possible recursive locking detected 4.19.211-syzkaller #0 Not tainted -------------------------------------------- syz-executor.1/11743 is trying to acquire lock: 00000000e3b4ef7e (&port_lock_key){-.-.}, at: uart_write+0x1ce/0x6f0 drivers/tty/serial/serial_core.c:591 but task is already holding lock: 00000000e3b4ef7e (&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.1/11743: #0: 000000006726c302 (&(&i->lock)->rlock){-.-.}, at: spin_lock include/linux/spinlock.h:329 [inline] #0: 000000006726c302 (&(&i->lock)->rlock){-.-.}, at: serial8250_interrupt+0x3a/0x240 drivers/tty/serial/8250/8250_core.c:115 #1: 00000000e3b4ef7e (&port_lock_key){-.-.}, at: serial8250_handle_irq.part.0+0x21/0x3d0 drivers/tty/serial/8250/8250_port.c:1876 #2: 000000007fa937ac (&tty->ldisc_sem){++++}, at: tty_ldisc_ref+0x1d/0x80 drivers/tty/tty_ldisc.c:293 stack backtrace: CPU: 1 PID: 11743 Comm: syz-executor.1 Not tainted 4.19.211-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 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:kmem_cache_free+0x11c/0x260 mm/slab.c:3766 Code: 11 48 63 75 74 48 89 df e8 51 21 df 01 e9 68 ff ff ff e8 a7 80 cf ff 48 83 3d e7 59 59 08 00 0f 84 f8 00 00 00 4c 89 e7 57 9d <0f> 1f 44 00 00 eb 86 65 8b 05 76 58 69 7e 83 f8 07 0f 87 e7 00 00 RSP: 0018:ffff888039dbfe08 EFLAGS: 00000286 ORIG_RAX: ffffffffffffffd5 RAX: 0000000000000007 RBX: ffff8880495ec940 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000286 RBP: ffff88823b843380 R08: 0000000000400000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000286 R13: ffffffff81a6b5c1 R14: 0000000000000020 R15: ffff8880adda65d0 putname+0xe1/0x120 fs/namei.c:261 do_sys_open+0x2ba/0x520 fs/open.c:1094 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x7fc700df3109 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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:00007fc6ff365168 EFLAGS: 00000246 ORIG_RAX: 0000000000000101 RAX: ffffffffffffffda RBX: 00007fc700f12f80 RCX: 00007fc700df3109 RDX: 0000000000000002 RSI: 0000000020000080 RDI: 00000000ffffff9c RBP: 00007fc700e4eae9 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffec8e0453f R14: 00007fc6ff365300 R15: 0000000000022000 ---------------- Code disassembly (best guess): 0: 11 48 63 adc %ecx,0x63(%rax) 3: 75 74 jne 0x79 5: 48 89 df mov %rbx,%rdi 8: e8 51 21 df 01 callq 0x1df215e d: e9 68 ff ff ff jmpq 0xffffff7a 12: e8 a7 80 cf ff callq 0xffcf80be 17: 48 83 3d e7 59 59 08 cmpq $0x0,0x85959e7(%rip) # 0x8595a06 1e: 00 1f: 0f 84 f8 00 00 00 je 0x11d 25: 4c 89 e7 mov %r12,%rdi 28: 57 push %rdi 29: 9d popfq * 2a: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) <-- trapping instruction 2f: eb 86 jmp 0xffffffb7 31: 65 8b 05 76 58 69 7e mov %gs:0x7e695876(%rip),%eax # 0x7e6958ae 38: 83 f8 07 cmp $0x7,%eax 3b: 0f .byte 0xf 3c: 87 e7 xchg %esp,%edi