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possible deadlock in serial8250_handle_irq (2)

Status: upstream: reported on 2025/07/16 08:44
Reported-by: syzbot+b623191c32404894a62a@syzkaller.appspotmail.com
First crash: 96d, last: 2d09h
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 possible deadlock in serial8250_handle_irq 4 2 127d 192d 0/3 auto-obsoleted due to no activity on 2025/09/22 18:06
upstream possible deadlock in serial8250_handle_irq hams 4 C 180 20d 821d 27/29 upstream: reported C repro on 2023/07/22 01:33
linux-6.6 possible deadlock in serial8250_handle_irq 4 2 105d 107d 0/2 auto-obsoleted due to no activity on 2025/10/14 13:08
linux-6.1 possible deadlock in serial8250_handle_irq 4 1 306d 306d 0/3 auto-obsoleted due to no activity on 2025/03/27 21:41
linux-5.15 possible deadlock in serial8250_handle_irq (2) 4 1 11d 11d 0/3 upstream: reported on 2025/10/09 00:28

Sample crash report:
=====================================================
WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected
syzkaller #0 Not tainted
-----------------------------------------------------
kworker/u4:8/4885 [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
  native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
  arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
  default_idle+0xb/0x10 arch/x86/kernel/process.c:741
  default_idle_call+0x84/0xc0 kernel/sched/idle.c:109
  cpuidle_idle_call kernel/sched/idle.c:191 [inline]
  do_idle+0x1fc/0x570 kernel/sched/idle.c:303
  cpu_startup_entry+0x3f/0x60 kernel/sched/idle.c:401
  rest_init+0x2dc/0x300 init/main.c:733
  start_kernel+0x0/0x539 init/main.c:893
  start_kernel+0x490/0x539 init/main.c:1140
  secondary_startup_64_no_verify+0xcf/0xdb

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/u4:8/4885:
 #0: ffff888017479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #1: ffffc900045cfd00 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267
 #2: ffff8880241f0ce8 (&buf->lock){+.+.}-{3:3}, at: flush_to_ldisc+0x34/0x860 drivers/tty/tty_buffer.c:537
 #3: ffff888027536098 (&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: ffff888027536098 (&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
                    native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
                    arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
                    default_idle+0xb/0x10 arch/x86/kernel/process.c:741
                    default_idle_call+0x84/0xc0 kernel/sched/idle.c:109
                    cpuidle_idle_call kernel/sched/idle.c:191 [inline]
                    do_idle+0x1fc/0x570 kernel/sched/idle.c:303
                    cpu_startup_entry+0x3f/0x60 kernel/sched/idle.c:401
                    rest_init+0x2dc/0x300 init/main.c:733
                    start_kernel+0x0/0x539 init/main.c:893
                    start_kernel+0x490/0x539 init/main.c:1140
                    secondary_startup_64_no_verify+0xcf/0xdb
   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+0x59/0xd0 arch/x86/kernel/irq.c:242
                    asm_common_interrupt+0x22/0x40 arch/x86/include/asm/idtentry.h:682
                    rcu_dynticks_curr_cpu_in_eqs include/linux/context_tracking.h:122 [inline]
                    rcu_is_watching+0x18/0xa0 kernel/rcu/tree.c:721
                    kernel_text_address+0x77/0xd0 kernel/extable.c:113
                    __kernel_text_address+0x9/0x30 kernel/extable.c:79
                    unwind_get_return_address+0x49/0x80 arch/x86/kernel/unwind_orc.c:323
                    arch_stack_walk+0xf2/0x140 arch/x86/kernel/stacktrace.c:26
                    stack_trace_save+0x98/0xe0 kernel/stacktrace.c:122
                    kasan_save_stack mm/kasan/common.c:45 [inline]
                    kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
                    kasan_save_free_info+0x2d/0x50 mm/kasan/generic.c:516
                    ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
                    kasan_slab_free include/linux/kasan.h:177 [inline]
                    slab_free_hook mm/slub.c:1729 [inline]
                    slab_free_freelist_hook+0x131/0x1a0 mm/slub.c:1755
                    slab_free mm/slub.c:3687 [inline]
                    kmem_cache_free+0xf7/0x290 mm/slub.c:3709
                    rcu_do_batch kernel/rcu/tree.c:2297 [inline]
                    rcu_core+0x9c0/0x16a0 kernel/rcu/tree.c:2557
                    handle_softirqs+0x2a1/0x920 kernel/softirq.c:596
                    __do_softirq kernel/softirq.c:630 [inline]
                    invoke_softirq kernel/softirq.c:470 [inline]
                    __irq_exit_rcu+0x12f/0x220 kernel/softirq.c:679
                    irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
                    instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
                    sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
                    asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
                    native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
                    arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
                    default_idle+0xb/0x10 arch/x86/kernel/process.c:741
                    default_idle_call+0x84/0xc0 kernel/sched/idle.c:109
                    cpuidle_idle_call kernel/sched/idle.c:191 [inline]
                    do_idle+0x1fc/0x570 kernel/sched/idle.c:303
                    cpu_startup_entry+0x3f/0x60 kernel/sched/idle.c:401
                    rest_init+0x2dc/0x300 init/main.c:733
                    start_kernel+0x0/0x539 init/main.c:893
                    start_kernel+0x490/0x539 init/main.c:1140
                    secondary_startup_64_no_verify+0xcf/0xdb
   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} {
   IN-HARDIRQ-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
                    serial8250_tx_chars+0x629/0x830 drivers/tty/serial/8250/8250_port.c:1854
                    serial8250_handle_irq+0x516/0x6d0 drivers/tty/serial/8250/8250_port.c:1961
                    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
                    native_irq_enable arch/x86/include/asm/irqflags.h:45 [inline]
                    arch_local_irq_enable arch/x86/include/asm/irqflags.h:80 [inline]
                    raw_spin_rq_unlock_irq kernel/sched/sched.h:1367 [inline]
                    finish_lock_switch kernel/sched/core.c:5003 [inline]
                    finish_task_switch+0x26a/0x8f0 kernel/sched/core.c:5121
                    context_switch kernel/sched/core.c:5247 [inline]
                    __schedule+0x10f4/0x40b0 kernel/sched/core.c:6561
                    schedule+0xb9/0x180 kernel/sched/core.c:6637
                    schedule_timeout+0x15c/0x280 kernel/time/timer.c:1965
                    rcu_gp_fqs_loop+0x2f2/0x1310 kernel/rcu/tree.c:1706
                    rcu_gp_kthread+0x95/0x380 kernel/rcu/tree.c:1905
                    kthread+0x29d/0x330 kernel/kthread.c:376
                    ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
   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: 4885 Comm: kworker/u4:8 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>

Crashes (11):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/10/18 00:06 linux-6.1.y c2fda4b3f577 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
2025/10/18 00:05 linux-6.1.y c2fda4b3f577 1c8c8cd8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
2025/09/30 23:40 linux-6.1.y 7b34dc04e4ff 65a0eece .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
2025/09/22 08:30 linux-6.1.y 363a599da6d9 67c37560 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
2025/09/09 21:31 linux-6.1.y f97f1002271b d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
2025/09/09 21:30 linux-6.1.y f97f1002271b d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
2025/08/15 12:31 linux-6.1.y 0bc96de781b4 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
2025/08/15 12:31 linux-6.1.y 0bc96de781b4 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
2025/08/08 03:30 linux-6.1.y 3594f306da12 6a893178 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
2025/07/28 15:53 linux-6.1.y 3594f306da12 6654ea9c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
2025/07/16 08:43 linux-6.1.y f2198ea7eb3e 124ec9cc .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan possible deadlock in serial8250_handle_irq
* Struck through repros no longer work on HEAD.