===================================================== WARNING: HARDIRQ-safe -> HARDIRQ-unsafe lock order detected syzkaller #0 Not tainted ----------------------------------------------------- kworker/u4:1/144 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire: ffffffff8ccce2b8 (disc_data_lock#2){.+.+}-{2:2}, at: sp_get drivers/net/hamradio/6pack.c:375 [inline] ffffffff8ccce2b8 (disc_data_lock#2){.+.+}-{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){.+.+}-{2:2} 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 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] _raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194 spin_unlock_irqrestore include/linux/spinlock.h:419 [inline] uart_write+0x62f/0x880 drivers/tty/serial/serial_core.c:592 process_output_block drivers/tty/n_tty.c:592 [inline] n_tty_write+0xd2e/0x1210 drivers/tty/n_tty.c:2339 do_tty_write drivers/tty/tty_io.c:1038 [inline] file_tty_write+0x557/0x910 drivers/tty/tty_io.c:1110 call_write_iter include/linux/fs.h:2173 [inline] new_sync_write fs/read_write.c:507 [inline] vfs_write+0x745/0xd60 fs/read_write.c:594 ksys_write+0x152/0x260 fs/read_write.c:647 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 to a HARDIRQ-irq-unsafe lock: (disc_data_lock#2){.+.+}-{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_receive_buf+0x4d/0x12f0 drivers/net/hamradio/6pack.c:438 tiocsti+0x1ea/0x270 drivers/tty/tty_io.c:2312 tty_ioctl+0x3a7/0xc20 drivers/tty/tty_io.c:2724 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#2); local_irq_disable(); lock(&port_lock_key); lock(disc_data_lock#2); lock(&port_lock_key); *** DEADLOCK *** 6 locks held by kworker/u4:1/144: #0: ffff888016c79138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x761/0x1010 kernel/workqueue.c:-1 #1: ffffc900010bfd00 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x79f/0x1010 kernel/workqueue.c:2285 #2: ffff8880204b8ca0 (&buf->lock){+.+.}-{3:3}, at: flush_to_ldisc+0x34/0x530 drivers/tty/tty_buffer.c:495 #3: ffff8880607d2098 (&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: ffff8880607d2098 (&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 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline] _raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194 spin_unlock_irqrestore include/linux/spinlock.h:419 [inline] uart_write+0x62f/0x880 drivers/tty/serial/serial_core.c:592 process_output_block drivers/tty/n_tty.c:592 [inline] n_tty_write+0xd2e/0x1210 drivers/tty/n_tty.c:2339 do_tty_write drivers/tty/tty_io.c:1038 [inline] file_tty_write+0x557/0x910 drivers/tty/tty_io.c:1110 call_write_iter include/linux/fs.h:2173 [inline] new_sync_write fs/read_write.c:507 [inline] vfs_write+0x745/0xd60 fs/read_write.c:594 ksys_write+0x152/0x260 fs/read_write.c:647 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 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_console_write+0x178/0x1000 drivers/tty/serial/8250/8250_port.c:3362 call_console_drivers kernel/printk/printk.c:-1 [inline] console_unlock+0xb9a/0x1120 kernel/printk/printk.c:2744 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274 dev_vprintk_emit+0x2e1/0x380 drivers/base/core.c:4638 dev_printk_emit+0xeb/0x140 drivers/base/core.c:4649 _dev_warn+0x11b/0x170 drivers/base/core.c:4705 qt2_process_read_urb drivers/usb/serial/quatech2.c:-1 [inline] qt2_read_bulk_callback+0x9ec/0xee0 drivers/usb/serial/quatech2.c:596 __usb_hcd_giveback_urb+0x35f/0x520 drivers/usb/core/hcd.c:1674 dummy_timer+0x8a8/0x31e0 drivers/usb/gadget/udc/dummy_hcd.c:1988 call_timer_fn+0x17b/0x540 kernel/time/timer.c:1648 expire_timers kernel/time/timer.c:1699 [inline] __run_timers+0x53e/0x800 kernel/time/timer.c:1970 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1983 handle_softirqs+0x339/0x830 kernel/softirq.c:576 __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 tomoyo_supervisor+0xf0a/0x11f0 security/tomoyo/common.c:2149 tomoyo_audit_path_log security/tomoyo/file.c:168 [inline] tomoyo_path_permission+0x25a/0x380 security/tomoyo/file.c:587 tomoyo_check_open_permission+0x275/0x410 security/tomoyo/file.c:777 security_file_open+0x5e/0xa0 security/security.c:1668 do_dentry_open+0x322/0xf80 fs/open.c:813 do_open fs/namei.c:3616 [inline] path_openat+0x26f5/0x2fa0 fs/namei.c:3750 do_filp_open+0x1e2/0x410 fs/namei.c:3777 do_sys_openat2+0x150/0x4b0 fs/open.c:1255 do_sys_open fs/open.c:1271 [inline] __do_sys_openat fs/open.c:1287 [inline] __se_sys_openat fs/open.c:1282 [inline] __x64_sys_openat+0x135/0x160 fs/open.c:1282 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_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){.+.+}-{2:2} { 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_receive_buf+0x4d/0x12f0 drivers/net/hamradio/6pack.c:438 tiocsti+0x1ea/0x270 drivers/tty/tty_io.c:2312 tty_ioctl+0x3a7/0xc20 drivers/tty/tty_io.c:2724 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_receive_buf+0x4d/0x12f0 drivers/net/hamradio/6pack.c:438 tiocsti+0x1ea/0x270 drivers/tty/tty_io.c:2312 tty_ioctl+0x3a7/0xc20 drivers/tty/tty_io.c:2724 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_release+0x170/0x200 drivers/tty/tty_ldisc.c:803 tty_release_struct+0x26/0xd0 drivers/tty/tty_io.c:1708 tty_release+0xd0c/0x16c0 drivers/tty/tty_io.c:1880 __fput+0x234/0x930 fs/file_table.c:311 task_work_run+0x125/0x1a0 kernel/task_work.c:188 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline] syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86 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_receive_buf+0x4d/0x12f0 drivers/net/hamradio/6pack.c:438 tiocsti+0x1ea/0x270 drivers/tty/tty_io.c:2312 tty_ioctl+0x3a7/0xc20 drivers/tty/tty_io.c:2724 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: 1 PID: 144 Comm: kworker/u4:1 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 attempt to access beyond end of device loop0: rw=2049, want=40976, limit=40427