===================================================== WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected 5.15.180-syzkaller #0 Not tainted ----------------------------------------------------- kworker/u4:8/4974 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: ffffffff8d4d7278 (disc_data_lock){.+.+}-{2:2}, at: sp_get drivers/net/hamradio/6pack.c:375 [inline] ffffffff8d4d7278 (disc_data_lock){.+.+}-{2:2}, at: sixpack_write_wakeup+0x2c/0x3c0 drivers/net/hamradio/6pack.c:396 and this task is already holding: ffffffff96dbf480 (&port_lock_key){-.-.}-{2:2}, at: uart_write+0x11e/0x930 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+0x1db/0x4f0 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162 serial8250_handle_irq+0x73/0x600 drivers/tty/serial/8250/8250_port.c:1895 serial8250_default_handle_irq+0xc8/0x1e0 drivers/tty/serial/8250/8250_port.c:1941 serial8250_interrupt+0xa1/0x1e0 drivers/tty/serial/8250/8250_core.c:127 __handle_irq_event_percpu+0x292/0xa70 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xff/0x2b0 kernel/irq/handle.c:213 handle_edge_irq+0x245/0xbf0 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+0xd7/0x1f0 arch/x86/kernel/irq.c:252 common_interrupt+0xae/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:722 default_idle_call+0x81/0xc0 kernel/sched/idle.c:112 cpuidle_idle_call kernel/sched/idle.c:194 [inline] do_idle+0x271/0x670 kernel/sched/idle.c:306 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:403 start_secondary+0x371/0x500 arch/x86/kernel/smpboot.c:281 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+0x1db/0x4f0 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_receive_buf+0x51/0x1430 drivers/net/hamradio/6pack.c:438 tty_ldisc_receive_buf+0x121/0x160 drivers/tty/tty_buffer.c:455 tty_port_default_receive_buf+0x6a/0x90 drivers/tty/tty_port.c:39 receive_buf drivers/tty/tty_buffer.c:471 [inline] flush_to_ldisc+0x2b9/0x540 drivers/tty/tty_buffer.c:523 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457 kthread+0x3f6/0x4f0 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 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/u4:8/4974: #0: ffff888017479138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x78a/0x10c0 kernel/workqueue.c:2283 #1: ffffc9000137fd20 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x7d0/0x10c0 kernel/workqueue.c:2285 #2: ffff888020518ca0 (&buf->lock){+.+.}-{3:3}, at: flush_to_ldisc+0x34/0x540 drivers/tty/tty_buffer.c:495 #3: ffff888020121098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x18/0x80 drivers/tty/tty_ldisc.c:273 #4: ffffffff96dbf480 (&port_lock_key){-.-.}-{2:2}, at: uart_write+0x11e/0x930 drivers/tty/serial/serial_core.c:571 #5: ffff888020121098 (&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+0x1db/0x4f0 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162 serial8250_handle_irq+0x73/0x600 drivers/tty/serial/8250/8250_port.c:1895 serial8250_default_handle_irq+0xc8/0x1e0 drivers/tty/serial/8250/8250_port.c:1941 serial8250_interrupt+0xa1/0x1e0 drivers/tty/serial/8250/8250_core.c:127 __handle_irq_event_percpu+0x292/0xa70 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xff/0x2b0 kernel/irq/handle.c:213 handle_edge_irq+0x245/0xbf0 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+0xd7/0x1f0 arch/x86/kernel/irq.c:252 common_interrupt+0xae/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:722 default_idle_call+0x81/0xc0 kernel/sched/idle.c:112 cpuidle_idle_call kernel/sched/idle.c:194 [inline] do_idle+0x271/0x670 kernel/sched/idle.c:306 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:403 start_secondary+0x371/0x500 arch/x86/kernel/smpboot.c:281 secondary_startup_64_no_verify+0xb1/0xbb IN-SOFTIRQ-W at: lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162 serial8250_handle_irq+0x73/0x600 drivers/tty/serial/8250/8250_port.c:1895 serial8250_default_handle_irq+0xc8/0x1e0 drivers/tty/serial/8250/8250_port.c:1941 serial8250_interrupt+0xa1/0x1e0 drivers/tty/serial/8250/8250_core.c:127 __handle_irq_event_percpu+0x292/0xa70 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xff/0x2b0 kernel/irq/handle.c:213 handle_edge_irq+0x245/0xbf0 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+0xd7/0x1f0 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 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] _raw_spin_unlock_irqrestore+0xd4/0x130 kernel/locking/spinlock.c:194 __mod_timer+0xa8e/0xeb0 kernel/time/timer.c:1065 call_timer_fn+0x16d/0x560 kernel/time/timer.c:1451 expire_timers kernel/time/timer.c:1496 [inline] __run_timers+0x67c/0x890 kernel/time/timer.c:1767 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1780 handle_softirqs+0x3a7/0x930 kernel/softirq.c:558 __do_softirq kernel/softirq.c:592 [inline] invoke_softirq kernel/softirq.c:432 [inline] __irq_exit_rcu+0x157/0x240 kernel/softirq.c:641 irq_exit_rcu+0x5/0x20 kernel/softirq.c:653 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:722 default_idle_call+0x81/0xc0 kernel/sched/idle.c:112 cpuidle_idle_call kernel/sched/idle.c:194 [inline] do_idle+0x271/0x670 kernel/sched/idle.c:306 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:403 start_secondary+0x371/0x500 arch/x86/kernel/smpboot.c:281 secondary_startup_64_no_verify+0xb1/0xbb INITIAL USE at: lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xd1/0x120 kernel/locking/spinlock.c:162 serial8250_do_set_termios+0x544/0x1830 drivers/tty/serial/8250/8250_port.c:2773 uart_set_options+0x3e1/0x740 drivers/tty/serial/serial_core.c:2154 serial8250_console_setup+0x3be/0x650 drivers/tty/serial/8250/8250_port.c:3448 univ8250_console_setup+0xe3/0x180 drivers/tty/serial/8250/8250_core.c:605 console_call_setup+0xd2/0xf0 kernel/printk/printk.c:2897 try_enable_preferred_console+0x3e3/0x530 kernel/printk/printk.c:2938 register_console+0x2ef/0x940 kernel/printk/printk.c:3037 univ8250_console_init+0x41/0x50 drivers/tty/serial/8250/8250_core.c:690 console_init+0x18c/0x660 kernel/printk/printk.c:3207 start_kernel+0x301/0x540 init/main.c:1076 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+0x1db/0x4f0 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_receive_buf+0x51/0x1430 drivers/net/hamradio/6pack.c:438 tty_ldisc_receive_buf+0x121/0x160 drivers/tty/tty_buffer.c:455 tty_port_default_receive_buf+0x6a/0x90 drivers/tty/tty_port.c:39 receive_buf drivers/tty/tty_buffer.c:471 [inline] flush_to_ldisc+0x2b9/0x540 drivers/tty/tty_buffer.c:523 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457 kthread+0x3f6/0x4f0 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 SOFTIRQ-ON-R at: lock_acquire+0x1db/0x4f0 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_receive_buf+0x51/0x1430 drivers/net/hamradio/6pack.c:438 tty_ldisc_receive_buf+0x121/0x160 drivers/tty/tty_buffer.c:455 tty_port_default_receive_buf+0x6a/0x90 drivers/tty/tty_port.c:39 receive_buf drivers/tty/tty_buffer.c:471 [inline] flush_to_ldisc+0x2b9/0x540 drivers/tty/tty_buffer.c:523 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457 kthread+0x3f6/0x4f0 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 INITIAL READ USE at: lock_acquire+0x1db/0x4f0 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_receive_buf+0x51/0x1430 drivers/net/hamradio/6pack.c:438 tty_ldisc_receive_buf+0x121/0x160 drivers/tty/tty_buffer.c:455 tty_port_default_receive_buf+0x6a/0x90 drivers/tty/tty_port.c:39 receive_buf drivers/tty/tty_buffer.c:471 [inline] flush_to_ldisc+0x2b9/0x540 drivers/tty/tty_buffer.c:523 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457 kthread+0x3f6/0x4f0 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 } ... key at: [] disc_data_lock+0x18/0x100 ... acquired at: lock_acquire+0x1db/0x4f0 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/0x3c0 drivers/net/hamradio/6pack.c:396 tty_wakeup+0xb3/0xf0 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0xa8/0x100 drivers/tty/tty_port.c:51 serial8250_tx_chars+0x60d/0x800 drivers/tty/serial/8250/8250_port.c:1828 __start_tx drivers/tty/serial/8250/8250_port.c:1548 [inline] serial8250_start_tx+0x722/0xa50 drivers/tty/serial/8250/8250_port.c:1652 __uart_start drivers/tty/serial/serial_core.c:132 [inline] uart_write+0x6a2/0x930 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+0x443/0x1430 drivers/net/hamradio/6pack.c:452 tty_ldisc_receive_buf+0x121/0x160 drivers/tty/tty_buffer.c:455 tty_port_default_receive_buf+0x6a/0x90 drivers/tty/tty_port.c:39 receive_buf drivers/tty/tty_buffer.c:471 [inline] flush_to_ldisc+0x2b9/0x540 drivers/tty/tty_buffer.c:523 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457 kthread+0x3f6/0x4f0 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 stack backtrace: CPU: 0 PID: 4974 Comm: kworker/u4:8 Not tainted 5.15.180-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Workqueue: events_unbound flush_to_ldisc Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1e3/0x2d0 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+0x4d01/0x5930 kernel/locking/lockdep.c:3788 __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012 lock_acquire+0x1db/0x4f0 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/0x3c0 drivers/net/hamradio/6pack.c:396 tty_wakeup+0xb3/0xf0 drivers/tty/tty_io.c:534 tty_port_default_wakeup+0xa8/0x100 drivers/tty/tty_port.c:51 serial8250_tx_chars+0x60d/0x800 drivers/tty/serial/8250/8250_port.c:1828 __start_tx drivers/tty/serial/8250/8250_port.c:1548 [inline] serial8250_start_tx+0x722/0xa50 drivers/tty/serial/8250/8250_port.c:1652 __uart_start drivers/tty/serial/serial_core.c:132 [inline] uart_write+0x6a2/0x930 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+0x443/0x1430 drivers/net/hamradio/6pack.c:452 tty_ldisc_receive_buf+0x121/0x160 drivers/tty/tty_buffer.c:455 tty_port_default_receive_buf+0x6a/0x90 drivers/tty/tty_port.c:39 receive_buf drivers/tty/tty_buffer.c:471 [inline] flush_to_ldisc+0x2b9/0x540 drivers/tty/tty_buffer.c:523 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457 kthread+0x3f6/0x4f0 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287