===================================================== WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected syzkaller #0 Not tainted ----------------------------------------------------- kworker/u4:8/5620 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: ffffffff8ccce2b8 (disc_data_lock){.+.+}-{2:2}, at: sp_get drivers/net/hamradio/6pack.c:375 [inline] ffffffff8ccce2b8 (disc_data_lock){.+.+}-{2:2}, at: sixpack_write_wakeup+0x2c/0x400 drivers/net/hamradio/6pack.c:396 and this task is already holding: ffffffff966012e0 (&port_lock_key){-.-.}-{2:2}, at: uart_write+0x105/0x880 drivers/tty/serial/serial_core.c:571 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+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xb0/0x100 kernel/locking/spinlock.c:162 serial8250_handle_irq+0x6c/0x610 drivers/tty/serial/8250/8250_port.c:1895 serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1941 serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:127 __handle_irq_event_percpu+0x299/0x9d0 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xa5/0x220 kernel/irq/handle.c:213 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:667 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:729 default_idle_call+0x81/0xc0 kernel/sched/idle.c:112 cpuidle_idle_call kernel/sched/idle.c:194 [inline] do_idle+0x21f/0x580 kernel/sched/idle.c:306 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:403 start_kernel+0x489/0x540 init/main.c:1154 secondary_startup_64_no_verify+0xb1/0xbb to a HARDIRQ-irq-unsafe lock: (disc_data_lock){.+.+}-{2:2} ... which became HARDIRQ-irq-unsafe at: ... lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228 sp_get drivers/net/hamradio/6pack.c:375 [inline] sixpack_write_wakeup+0x2c/0x400 drivers/net/hamradio/6pack.c:396 tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0xa5/0xf0 drivers/tty/tty_port.c:51 tty_ldisc_hangup+0xd6/0x4a0 drivers/tty/tty_ldisc.c:720 __tty_hangup+0x45c/0x680 drivers/tty/tty_io.c:639 tty_vhangup drivers/tty/tty_io.c:711 [inline] tty_ioctl+0x489/0xc20 drivers/tty/tty_io.c:2750 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 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); lock(&port_lock_key); *** DEADLOCK *** 6 locks held by kworker/u4:8/5620: #0: ffff888016c79138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x761/0x1010 kernel/workqueue.c:-1 #1: ffffc900030f7d00 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x79f/0x1010 kernel/workqueue.c:2285 #2: ffff88801f978ca0 (&buf->lock){+.+.}-{3:3}, at: flush_to_ldisc+0x34/0x530 drivers/tty/tty_buffer.c:495 #3: ffff88806218f098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x18/0x80 drivers/tty/tty_ldisc.c:273 #4: ffffffff966012e0 (&port_lock_key){-.-.}-{2:2}, at: uart_write+0x105/0x880 drivers/tty/serial/serial_core.c:571 #5: ffff88806218f098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x18/0x80 drivers/tty/tty_ldisc.c:273 the dependencies between HARDIRQ-irq-safe lock and the holding lock: -> (&port_lock_key){-.-.}-{2:2} { IN-HARDIRQ-W at: lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xb0/0x100 kernel/locking/spinlock.c:162 serial8250_handle_irq+0x6c/0x610 drivers/tty/serial/8250/8250_port.c:1895 serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1941 serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:127 __handle_irq_event_percpu+0x299/0x9d0 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xa5/0x220 kernel/irq/handle.c:213 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:667 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:729 default_idle_call+0x81/0xc0 kernel/sched/idle.c:112 cpuidle_idle_call kernel/sched/idle.c:194 [inline] do_idle+0x21f/0x580 kernel/sched/idle.c:306 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:403 start_kernel+0x489/0x540 init/main.c:1154 secondary_startup_64_no_verify+0xb1/0xbb IN-SOFTIRQ-W at: lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xb0/0x100 kernel/locking/spinlock.c:162 serial8250_handle_irq+0x6c/0x610 drivers/tty/serial/8250/8250_port.c:1895 serial8250_default_handle_irq+0xb4/0x1a0 drivers/tty/serial/8250/8250_port.c:1941 serial8250_interrupt+0x9b/0x1c0 drivers/tty/serial/8250/8250_core.c:127 __handle_irq_event_percpu+0x299/0x9d0 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xa5/0x220 kernel/irq/handle.c:213 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:667 ffs arch/x86/include/asm/bitops.h:297 [inline] handle_softirqs+0x1a9/0x830 kernel/softirq.c:564 __do_softirq kernel/softirq.c:610 [inline] invoke_softirq kernel/softirq.c:450 [inline] __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline] sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676 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:729 default_idle_call+0x81/0xc0 kernel/sched/idle.c:112 cpuidle_idle_call kernel/sched/idle.c:194 [inline] do_idle+0x21f/0x580 kernel/sched/idle.c:306 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:403 start_kernel+0x489/0x540 init/main.c:1154 secondary_startup_64_no_verify+0xb1/0xbb INITIAL USE at: lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xb0/0x100 kernel/locking/spinlock.c:162 serial8250_do_set_termios+0x54b/0x1850 drivers/tty/serial/8250/8250_port.c:2772 uart_set_options+0x3d1/0x5e0 drivers/tty/serial/serial_core.c:2154 serial8250_console_setup+0x2bc/0x3a0 drivers/tty/serial/8250/8250_port.c:3447 univ8250_console_setup+0xe9/0x180 drivers/tty/serial/8250/8250_core.c:605 console_call_setup+0xd3/0xf0 kernel/printk/printk.c:2897 try_enable_preferred_console+0x43c/0x5a0 kernel/printk/printk.c:2938 register_console+0x2fd/0x980 kernel/printk/printk.c:3037 univ8250_console_init+0x41/0x50 drivers/tty/serial/8250/8250_core.c:690 console_init+0x177/0x5d0 kernel/printk/printk.c:3207 start_kernel+0x2fc/0x540 init/main.c:1090 secondary_startup_64_no_verify+0xb1/0xbb } ... key at: [] 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+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228 sp_get drivers/net/hamradio/6pack.c:375 [inline] sixpack_write_wakeup+0x2c/0x400 drivers/net/hamradio/6pack.c:396 tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0xa5/0xf0 drivers/tty/tty_port.c:51 tty_ldisc_hangup+0xd6/0x4a0 drivers/tty/tty_ldisc.c:720 __tty_hangup+0x45c/0x680 drivers/tty/tty_io.c:639 tty_vhangup drivers/tty/tty_io.c:711 [inline] tty_ioctl+0x489/0xc20 drivers/tty/tty_io.c:2750 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 SOFTIRQ-ON-R at: lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228 sp_get drivers/net/hamradio/6pack.c:375 [inline] sixpack_write_wakeup+0x2c/0x400 drivers/net/hamradio/6pack.c:396 tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0xa5/0xf0 drivers/tty/tty_port.c:51 tty_ldisc_hangup+0xd6/0x4a0 drivers/tty/tty_ldisc.c:720 __tty_hangup+0x45c/0x680 drivers/tty/tty_io.c:639 tty_vhangup drivers/tty/tty_io.c:711 [inline] tty_ioctl+0x489/0xc20 drivers/tty/tty_io.c:2750 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 INITIAL USE at: lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_write_lock_irq include/linux/rwlock_api_smp.h:196 [inline] _raw_write_lock_irq+0xab/0xf0 kernel/locking/spinlock.c:316 sixpack_close+0x28/0x1e0 drivers/net/hamradio/6pack.c:651 tty_ldisc_kill+0xa6/0x1a0 drivers/tty/tty_ldisc.c:629 tty_ldisc_hangup+0x392/0x4a0 drivers/tty/tty_ldisc.c:749 __tty_hangup+0x45c/0x680 drivers/tty/tty_io.c:639 tty_vhangup drivers/tty/tty_io.c:711 [inline] tty_ioctl+0x489/0xc20 drivers/tty/tty_io.c:2750 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 INITIAL READ USE at: lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228 sp_get drivers/net/hamradio/6pack.c:375 [inline] sixpack_write_wakeup+0x2c/0x400 drivers/net/hamradio/6pack.c:396 tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0xa5/0xf0 drivers/tty/tty_port.c:51 tty_ldisc_hangup+0xd6/0x4a0 drivers/tty/tty_ldisc.c:720 __tty_hangup+0x45c/0x680 drivers/tty/tty_io.c:639 tty_vhangup drivers/tty/tty_io.c:711 [inline] tty_ioctl+0x489/0xc20 drivers/tty/tty_io.c:2750 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x66/0xd0 } ... key at: [] disc_data_lock+0x18/0x100 ... acquired at: __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228 sp_get drivers/net/hamradio/6pack.c:375 [inline] sixpack_write_wakeup+0x2c/0x400 drivers/net/hamradio/6pack.c:396 tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0xa5/0xf0 drivers/tty/tty_port.c:51 serial8250_tx_chars+0x629/0x830 drivers/tty/serial/8250/8250_port.c:1828 __start_tx drivers/tty/serial/8250/8250_port.c:1548 [inline] serial8250_start_tx+0x7e9/0xa20 drivers/tty/serial/8250/8250_port.c:1652 __uart_start drivers/tty/serial/serial_core.c:132 [inline] uart_write+0x61e/0x880 drivers/tty/serial/serial_core.c:591 decode_prio_command drivers/net/hamradio/6pack.c:886 [inline] sixpack_decode drivers/net/hamradio/6pack.c:959 [inline] sixpack_receive_buf+0x421/0x12f0 drivers/net/hamradio/6pack.c:452 tty_ldisc_receive_buf+0x113/0x150 drivers/tty/tty_buffer.c:455 tty_port_default_receive_buf+0x69/0x90 drivers/tty/tty_port.c:39 receive_buf drivers/tty/tty_buffer.c:471 [inline] flush_to_ldisc+0x2a7/0x530 drivers/tty/tty_buffer.c:523 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457 kthread+0x436/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 stack backtrace: CPU: 0 PID: 5620 Comm: kworker/u4:8 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Workqueue: events_unbound flush_to_ldisc Call Trace: dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106 print_bad_irq_dependency kernel/locking/lockdep.c:2567 [inline] check_irq_usage kernel/locking/lockdep.c:2806 [inline] check_prev_add kernel/locking/lockdep.c:3057 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x6688/0x7d10 kernel/locking/lockdep.c:5012 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623 __raw_read_lock include/linux/rwlock_api_smp.h:149 [inline] _raw_read_lock+0x32/0x40 kernel/locking/spinlock.c:228 sp_get drivers/net/hamradio/6pack.c:375 [inline] sixpack_write_wakeup+0x2c/0x400 drivers/net/hamradio/6pack.c:396 tty_wakeup+0xb4/0xf0 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0xa5/0xf0 drivers/tty/tty_port.c:51 serial8250_tx_chars+0x629/0x830 drivers/tty/serial/8250/8250_port.c:1828 __start_tx drivers/tty/serial/8250/8250_port.c:1548 [inline] serial8250_start_tx+0x7e9/0xa20 drivers/tty/serial/8250/8250_port.c:1652 __uart_start drivers/tty/serial/serial_core.c:132 [inline] uart_write+0x61e/0x880 drivers/tty/serial/serial_core.c:591 decode_prio_command drivers/net/hamradio/6pack.c:886 [inline] sixpack_decode drivers/net/hamradio/6pack.c:959 [inline] sixpack_receive_buf+0x421/0x12f0 drivers/net/hamradio/6pack.c:452 tty_ldisc_receive_buf+0x113/0x150 drivers/tty/tty_buffer.c:455 tty_port_default_receive_buf+0x69/0x90 drivers/tty/tty_port.c:39 receive_buf drivers/tty/tty_buffer.c:471 [inline] flush_to_ldisc+0x2a7/0x530 drivers/tty/tty_buffer.c:523 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457 kthread+0x436/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287