=====================================================
WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
syzkaller #0 Not tainted
-----------------------------------------------------
kworker/u4:1/11 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
ffffffff8d5910f8 (disc_data_lock){.+.+}-{2:2}, at: sp_get drivers/net/hamradio/6pack.c:376 [inline]
ffffffff8d5910f8 (disc_data_lock){.+.+}-{2:2}, at: sixpack_write_wakeup+0x2c/0x460 drivers/net/hamradio/6pack.c:397

and this task is already holding:
ffffffff96f70fa8 (&port_lock_key){-.-.}-{2:2}, at: uart_write+0x113/0x910 drivers/tty/serial/serial_core.c:581
which would create a new lock dependency:
 (&port_lock_key){-.-.}-{2:2} -> (disc_data_lock){.+.+}-{2:2}

but this new dependency connects a HARDIRQ-irq-safe lock:
 (&port_lock_key){-.-.}-{2:2}

... which became HARDIRQ-irq-safe at:
  lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
  _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
  serial8250_handle_irq+0x7a/0x6d0 drivers/tty/serial/8250/8250_port.c:1932
  serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1981
  serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:126
  __handle_irq_event_percpu+0x298/0xa30 kernel/irq/handle.c:158
  handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
  handle_irq_event+0x87/0x1e0 kernel/irq/handle.c:210
  handle_edge_irq+0x243/0xb20 kernel/irq/chip.c:819
  generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
  handle_irq arch/x86/kernel/irq.c:233 [inline]
  __common_interrupt+0xd7/0x1e0 arch/x86/kernel/irq.c:252
  common_interrupt+0xb0/0xd0 arch/x86/kernel/irq.c:242
  asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:682
  __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
  _raw_spin_unlock_irqrestore+0xa5/0x100 kernel/locking/spinlock.c:194
  spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
  uart_write+0x68a/0x910 drivers/tty/serial/serial_core.c:602
  process_output_block drivers/tty/n_tty.c:586 [inline]
  n_tty_write+0xd1a/0x11c0 drivers/tty/n_tty.c:2377
  do_tty_write drivers/tty/tty_io.c:1018 [inline]
  file_tty_write+0x4dd/0x860 drivers/tty/tty_io.c:1089
  call_write_iter include/linux/fs.h:2265 [inline]
  new_sync_write fs/read_write.c:491 [inline]
  vfs_write+0x44c/0x960 fs/read_write.c:584
  ksys_write+0x143/0x240 fs/read_write.c:637
  do_syscall_x64 arch/x86/entry/common.c:51 [inline]
  do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
  entry_SYSCALL_64_after_hwframe+0x68/0xd2

to a HARDIRQ-irq-unsafe lock:
 (disc_data_lock){.+.+}-{2:2}

... which became HARDIRQ-irq-unsafe at:
...
  lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
  __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
  _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228
  sp_get drivers/net/hamradio/6pack.c:376 [inline]
  sixpack_write_wakeup+0x2c/0x460 drivers/net/hamradio/6pack.c:397
  tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:524
  tty_port_default_wakeup+0x9e/0xf0 drivers/tty/tty_port.c:71
  tty_ldisc_hangup+0xd6/0x4a0 drivers/tty/tty_ldisc.c:701
  __tty_hangup+0x3e5/0x620 drivers/tty/tty_io.c:631
  tty_vhangup drivers/tty/tty_io.c:701 [inline]
  tty_ioctl+0x430/0xba0 drivers/tty/tty_io.c:2716
  vfs_ioctl fs/ioctl.c:51 [inline]
  __do_sys_ioctl fs/ioctl.c:870 [inline]
  __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
  do_syscall_x64 arch/x86/entry/common.c:51 [inline]
  do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
  entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

 Possible interrupt unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(disc_data_lock);
                               local_irq_disable();
                               lock(&port_lock_key);
                               lock(disc_data_lock);
  <Interrupt>
    lock(&port_lock_key);

 *** DEADLOCK ***

6 locks held by kworker/u4:1/11:
 #0: ffff888017479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc90000107d00 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff888023d90ce8 (&buf->lock){+.+.}-{3:3}, at: flush_to_ldisc+0x34/0x860 drivers/tty/tty_buffer.c:537
 #3: ffff888056b38098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x18/0x80 drivers/tty/tty_ldisc.c:264
 #4: ffffffff96f70fa8 (&port_lock_key){-.-.}-{2:2}, at: uart_write+0x113/0x910 drivers/tty/serial/serial_core.c:581
 #5: ffff888056b38098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x18/0x80 drivers/tty/tty_ldisc.c:264

the dependencies between HARDIRQ-irq-safe lock and the holding lock:
-> (&port_lock_key){-.-.}-{2:2} {
   IN-HARDIRQ-W at:
                    lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
                    __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
                    _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
                    serial8250_handle_irq+0x7a/0x6d0 drivers/tty/serial/8250/8250_port.c:1932
                    serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1981
                    serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:126
                    __handle_irq_event_percpu+0x298/0xa30 kernel/irq/handle.c:158
                    handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
                    handle_irq_event+0x87/0x1e0 kernel/irq/handle.c:210
                    handle_edge_irq+0x243/0xb20 kernel/irq/chip.c:819
                    generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
                    handle_irq arch/x86/kernel/irq.c:233 [inline]
                    __common_interrupt+0xd7/0x1e0 arch/x86/kernel/irq.c:252
                    common_interrupt+0xb0/0xd0 arch/x86/kernel/irq.c:242
                    asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:682
                    __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
                    _raw_spin_unlock_irqrestore+0xa5/0x100 kernel/locking/spinlock.c:194
                    spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
                    uart_write+0x68a/0x910 drivers/tty/serial/serial_core.c:602
                    process_output_block drivers/tty/n_tty.c:586 [inline]
                    n_tty_write+0xd1a/0x11c0 drivers/tty/n_tty.c:2377
                    do_tty_write drivers/tty/tty_io.c:1018 [inline]
                    file_tty_write+0x4dd/0x860 drivers/tty/tty_io.c:1089
                    call_write_iter include/linux/fs.h:2265 [inline]
                    new_sync_write fs/read_write.c:491 [inline]
                    vfs_write+0x44c/0x960 fs/read_write.c:584
                    ksys_write+0x143/0x240 fs/read_write.c:637
                    do_syscall_x64 arch/x86/entry/common.c:51 [inline]
                    do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
                    entry_SYSCALL_64_after_hwframe+0x68/0xd2
   IN-SOFTIRQ-W at:
                    lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
                    __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
                    _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
                    serial8250_handle_irq+0x7a/0x6d0 drivers/tty/serial/8250/8250_port.c:1932
                    serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1981
                    serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:126
                    __handle_irq_event_percpu+0x298/0xa30 kernel/irq/handle.c:158
                    handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
                    handle_irq_event+0x87/0x1e0 kernel/irq/handle.c:210
                    handle_edge_irq+0x243/0xb20 kernel/irq/chip.c:819
                    generic_handle_irq_desc include/linux/irqdesc.h:158 [inline]
                    handle_irq arch/x86/kernel/irq.c:233 [inline]
                    __common_interrupt+0xd7/0x1e0 arch/x86/kernel/irq.c:252
                    common_interrupt+0xb0/0xd0 arch/x86/kernel/irq.c:242
                    asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:682
                    invoke_rcu_core+0x67/0x240 kernel/rcu/tree.c:2604
                    rcu_core+0x104e/0x16a0 kernel/rcu/tree.c:2560
                    handle_softirqs+0x2a1/0x920 kernel/softirq.c:596
                    run_ksoftirqd+0x98/0xf0 kernel/softirq.c:963
                    smpboot_thread_fn+0x64a/0xa40 kernel/smpboot.c:164
                    kthread+0x29d/0x330 kernel/kthread.c:376
                    ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
   INITIAL USE at:
                   lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
                   __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
                   _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162
                   serial8250_do_set_termios+0x544/0x17d0 drivers/tty/serial/8250/8250_port.c:2794
                   uart_set_options+0x3c2/0x5d0 drivers/tty/serial/serial_core.c:2283
                   serial8250_console_setup+0x2ce/0x3a0 drivers/tty/serial/8250/8250_port.c:3536
                   univ8250_console_setup+0xe9/0x180 drivers/tty/serial/8250/8250_core.c:602
                   console_call_setup kernel/printk/printk.c:3063 [inline]
                   try_enable_preferred_console+0x48a/0x600 kernel/printk/printk.c:3104
                   register_console+0x1b0/0x9c0 kernel/printk/printk.c:3211
                   univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:687
                   console_init+0x1bc/0x78e kernel/printk/printk.c:3359
                   start_kernel+0x303/0x539 init/main.c:1076
                   secondary_startup_64_no_verify+0xcf/0xdb
 }
 ... key      at: [<ffffffff96f70440>] port_lock_key+0x0/0x20

the dependencies between the lock to be acquired
 and HARDIRQ-irq-unsafe lock:
-> (disc_data_lock){.+.+}-{2:2} {
   HARDIRQ-ON-R at:
                    lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
                    __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
                    _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228
                    sp_get drivers/net/hamradio/6pack.c:376 [inline]
                    sixpack_write_wakeup+0x2c/0x460 drivers/net/hamradio/6pack.c:397
                    tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:524
                    tty_port_default_wakeup+0x9e/0xf0 drivers/tty/tty_port.c:71
                    tty_ldisc_hangup+0xd6/0x4a0 drivers/tty/tty_ldisc.c:701
                    __tty_hangup+0x3e5/0x620 drivers/tty/tty_io.c:631
                    tty_vhangup drivers/tty/tty_io.c:701 [inline]
                    tty_ioctl+0x430/0xba0 drivers/tty/tty_io.c:2716
                    vfs_ioctl fs/ioctl.c:51 [inline]
                    __do_sys_ioctl fs/ioctl.c:870 [inline]
                    __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
                    do_syscall_x64 arch/x86/entry/common.c:51 [inline]
                    do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
                    entry_SYSCALL_64_after_hwframe+0x68/0xd2
   SOFTIRQ-ON-R at:
                    lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
                    __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
                    _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228
                    sp_get drivers/net/hamradio/6pack.c:376 [inline]
                    sixpack_write_wakeup+0x2c/0x460 drivers/net/hamradio/6pack.c:397
                    tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:524
                    tty_port_default_wakeup+0x9e/0xf0 drivers/tty/tty_port.c:71
                    tty_ldisc_hangup+0xd6/0x4a0 drivers/tty/tty_ldisc.c:701
                    __tty_hangup+0x3e5/0x620 drivers/tty/tty_io.c:631
                    tty_vhangup drivers/tty/tty_io.c:701 [inline]
                    tty_ioctl+0x430/0xba0 drivers/tty/tty_io.c:2716
                    vfs_ioctl fs/ioctl.c:51 [inline]
                    __do_sys_ioctl fs/ioctl.c:870 [inline]
                    __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
                    do_syscall_x64 arch/x86/entry/common.c:51 [inline]
                    do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
                    entry_SYSCALL_64_after_hwframe+0x68/0xd2
   INITIAL USE at:
                   lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
                   __raw_write_lock_irq include/linux/rwlock_api_smp.h:195 [inline]
                   _raw_write_lock_irq+0x9f/0xe0 kernel/locking/spinlock.c:326
                   sixpack_close+0x28/0x290 drivers/net/hamradio/6pack.c:653
                   tty_ldisc_kill+0xa6/0x1a0 drivers/tty/tty_ldisc.c:614
                   tty_ldisc_hangup+0x392/0x4a0 drivers/tty/tty_ldisc.c:730
                   __tty_hangup+0x3e5/0x620 drivers/tty/tty_io.c:631
                   tty_vhangup drivers/tty/tty_io.c:701 [inline]
                   tty_ioctl+0x430/0xba0 drivers/tty/tty_io.c:2716
                   vfs_ioctl fs/ioctl.c:51 [inline]
                   __do_sys_ioctl fs/ioctl.c:870 [inline]
                   __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
                   do_syscall_x64 arch/x86/entry/common.c:51 [inline]
                   do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
                   entry_SYSCALL_64_after_hwframe+0x68/0xd2
   INITIAL READ USE at:
                        lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
                        __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
                        _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228
                        sp_get drivers/net/hamradio/6pack.c:376 [inline]
                        sixpack_write_wakeup+0x2c/0x460 drivers/net/hamradio/6pack.c:397
                        tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:524
                        tty_port_default_wakeup+0x9e/0xf0 drivers/tty/tty_port.c:71
                        tty_ldisc_hangup+0xd6/0x4a0 drivers/tty/tty_ldisc.c:701
                        __tty_hangup+0x3e5/0x620 drivers/tty/tty_io.c:631
                        tty_vhangup drivers/tty/tty_io.c:701 [inline]
                        tty_ioctl+0x430/0xba0 drivers/tty/tty_io.c:2716
                        vfs_ioctl fs/ioctl.c:51 [inline]
                        __do_sys_ioctl fs/ioctl.c:870 [inline]
                        __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:856
                        do_syscall_x64 arch/x86/entry/common.c:51 [inline]
                        do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
                        entry_SYSCALL_64_after_hwframe+0x68/0xd2
 }
 ... key      at: [<ffffffff8d5910f8>] disc_data_lock+0x18/0x100
 ... acquired at:
   __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
   _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228
   sp_get drivers/net/hamradio/6pack.c:376 [inline]
   sixpack_write_wakeup+0x2c/0x460 drivers/net/hamradio/6pack.c:397
   tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:524
   tty_port_default_wakeup+0x9e/0xf0 drivers/tty/tty_port.c:71
   serial8250_tx_chars+0x629/0x830 drivers/tty/serial/8250/8250_port.c:1854
   __start_tx drivers/tty/serial/8250/8250_port.c:1570 [inline]
   serial8250_start_tx+0x6a9/0x8a0 drivers/tty/serial/8250/8250_port.c:1676
   __uart_start drivers/tty/serial/serial_core.c:139 [inline]
   uart_write+0x67d/0x910 drivers/tty/serial/serial_core.c:601
   decode_prio_command drivers/net/hamradio/6pack.c:888 [inline]
   sixpack_decode drivers/net/hamradio/6pack.c:963 [inline]
   sixpack_receive_buf+0x438/0x1430 drivers/net/hamradio/6pack.c:453
   tty_ldisc_receive_buf+0x113/0x150 drivers/tty/tty_buffer.c:461
   tty_port_default_receive_buf+0x69/0x90 drivers/tty/tty_port.c:39
   receive_buf drivers/tty/tty_buffer.c:515 [inline]
   flush_to_ldisc+0x2f7/0x860 drivers/tty/tty_buffer.c:565
   process_one_work+0x898/0x1160 kernel/workqueue.c:2292
   worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
   kthread+0x29d/0x330 kernel/kthread.c:376
   ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295


stack backtrace:
CPU: 1 PID: 11 Comm: kworker/u4:1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 print_bad_irq_dependency kernel/locking/lockdep.c:2604 [inline]
 check_irq_usage kernel/locking/lockdep.c:2843 [inline]
 check_prev_add kernel/locking/lockdep.c:3094 [inline]
 check_prevs_add kernel/locking/lockdep.c:3209 [inline]
 validate_chain kernel/locking/lockdep.c:3825 [inline]
 __lock_acquire+0x660b/0x7c50 kernel/locking/lockdep.c:5049
 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662
 __raw_read_lock include/linux/rwlock_api_smp.h:150 [inline]
 _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228
 sp_get drivers/net/hamradio/6pack.c:376 [inline]
 sixpack_write_wakeup+0x2c/0x460 drivers/net/hamradio/6pack.c:397
 tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:524
 tty_port_default_wakeup+0x9e/0xf0 drivers/tty/tty_port.c:71
 serial8250_tx_chars+0x629/0x830 drivers/tty/serial/8250/8250_port.c:1854
 __start_tx drivers/tty/serial/8250/8250_port.c:1570 [inline]
 serial8250_start_tx+0x6a9/0x8a0 drivers/tty/serial/8250/8250_port.c:1676
 __uart_start drivers/tty/serial/serial_core.c:139 [inline]
 uart_write+0x67d/0x910 drivers/tty/serial/serial_core.c:601
 decode_prio_command drivers/net/hamradio/6pack.c:888 [inline]
 sixpack_decode drivers/net/hamradio/6pack.c:963 [inline]
 sixpack_receive_buf+0x438/0x1430 drivers/net/hamradio/6pack.c:453
 tty_ldisc_receive_buf+0x113/0x150 drivers/tty/tty_buffer.c:461
 tty_port_default_receive_buf+0x69/0x90 drivers/tty/tty_port.c:39
 receive_buf drivers/tty/tty_buffer.c:515 [inline]
 flush_to_ldisc+0x2f7/0x860 drivers/tty/tty_buffer.c:565
 process_one_work+0x898/0x1160 kernel/workqueue.c:2292
 worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>