====================================================== WARNING: possible circular locking dependency detected 5.15.184-syzkaller #0 Not tainted ------------------------------------------------------ kworker/u4:5/4229 is trying to acquire lock: ffff88801de7c5a8 (&p->pi_lock){-.-.}-{2:2}, at: try_to_wake_up+0x5c/0x1050 kernel/sched/core.c:4030 but task is already holding lock: ffff88807925e528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:137 [inline] ffff88807925e528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up+0xed/0x180 kernel/sched/wait.c:157 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&tty->write_wait){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 __wake_up_common_lock kernel/sched/wait.c:137 [inline] __wake_up+0xed/0x180 kernel/sched/wait.c:157 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 serial8250_handle_irq+0x519/0x610 drivers/tty/serial/8250/8250_port.c:1924 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+0x291/0x9b0 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+0xa5/0x100 kernel/locking/spinlock.c:194 spin_unlock_irqrestore include/linux/spinlock.h:418 [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+0xd21/0x1210 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:2172 [inline] new_sync_write fs/read_write.c:507 [inline] vfs_write+0x712/0xd00 fs/read_write.c:594 ksys_write+0x14d/0x250 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 -> #3 (&port_lock_key){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 serial8250_console_write+0x170/0xf80 drivers/tty/serial/8250/8250_port.c:3363 call_console_drivers kernel/printk/printk.c:-1 [inline] console_unlock+0xc86/0x1200 kernel/printk/printk.c:2744 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274 _printk+0xcc/0x110 kernel/printk/printk.c:2299 register_console+0x682/0x960 kernel/printk/printk.c:3107 univ8250_console_init+0x41/0x50 drivers/tty/serial/8250/8250_core.c:690 console_init+0x177/0x5d0 kernel/printk/printk.c:3207 start_kernel+0x2f9/0x530 init/main.c:1076 secondary_startup_64_no_verify+0xb1/0xbb -> #2 (console_owner){-...}-{0:0}: console_lock_spinning_enable+0x51/0x60 kernel/printk/printk.c:1805 console_unlock+0x9f8/0x1200 kernel/printk/printk.c:2741 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274 _printk+0xcc/0x110 kernel/printk/printk.c:2299 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x36d/0x4c0 lib/fault-inject.c:146 strncpy_from_user+0x32/0x360 lib/strncpy_from_user.c:118 strncpy_from_user_nofault+0x6d/0x140 mm/maccess.c:295 bpf_probe_read_user_str_common kernel/trace/bpf_trace.c:194 [inline] ____bpf_probe_read_compat_str kernel/trace/bpf_trace.c:300 [inline] bpf_probe_read_compat_str+0xdd/0x170 kernel/trace/bpf_trace.c:296 0xffffffffa002ebb1 bpf_dispatcher_nop_func include/linux/bpf.h:790 [inline] __bpf_prog_run include/linux/filter.h:628 [inline] bpf_prog_run include/linux/filter.h:635 [inline] __bpf_trace_run kernel/trace/bpf_trace.c:1878 [inline] bpf_trace_run3+0x17e/0x320 kernel/trace/bpf_trace.c:1916 trace_sched_switch include/trace/events/sched.h:220 [inline] __schedule+0x1d8b/0x43b0 kernel/sched/core.c:6373 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6780 irqentry_exit+0x63/0x70 kernel/entry/common.c:432 asm_sysvec_reschedule_ipi+0x16/0x20 arch/x86/include/asm/idtentry.h:681 native_save_fl arch/x86/include/asm/irqflags.h:35 [inline] arch_local_save_flags arch/x86/include/asm/irqflags.h:70 [inline] arch_local_irq_save arch/x86/include/asm/irqflags.h:106 [inline] lock_is_held_type+0x68/0x190 kernel/locking/lockdep.c:5662 lock_is_held include/linux/lockdep.h:287 [inline] ___might_sleep+0xf2/0x600 kernel/sched/core.c:9605 __mutex_lock_common+0xc1/0x2390 kernel/locking/mutex.c:573 __mutex_lock kernel/locking/mutex.c:729 [inline] mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743 __fdget_pos+0x2bf/0x370 fs/file.c:1058 fdget_pos include/linux/file.h:75 [inline] ksys_write+0x78/0x250 fs/read_write.c:638 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 -> #1 (&rq->__lock){-.-.}-{2:2}: _raw_spin_lock_nested+0x2e/0x40 kernel/locking/spinlock.c:368 raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:475 raw_spin_rq_lock kernel/sched/sched.h:1326 [inline] rq_lock kernel/sched/sched.h:1621 [inline] task_fork_fair+0x5c/0x350 kernel/sched/fair.c:11499 sched_cgroup_fork+0x2c6/0x320 kernel/sched/core.c:4466 copy_process+0x22bd/0x3e60 kernel/fork.c:2319 kernel_clone+0x219/0x930 kernel/fork.c:2603 kernel_thread+0xc8/0x120 kernel/fork.c:2655 rest_init+0x21/0x330 init/main.c:706 start_kernel+0x486/0x530 init/main.c:1140 secondary_startup_64_no_verify+0xb1/0xbb -> #0 (&p->pi_lock){-.-.}-{2:2}: check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 try_to_wake_up+0x5c/0x1050 kernel/sched/core.c:4030 __wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:108 __wake_up_common_lock kernel/sched/wait.c:138 [inline] __wake_up+0x108/0x180 kernel/sched/wait.c:157 pty_unthrottle+0x38/0x60 drivers/tty/pty.c:95 tty_unthrottle_safe+0x109/0x160 drivers/tty/tty_ioctl.c:178 n_tty_receive_buf_common+0x60db/0x6480 drivers/tty/n_tty.c:1689 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+0x863/0x1000 kernel/workqueue.c:2310 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457 kthread+0x436/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 other info that might help us debug this: Chain exists of: &p->pi_lock --> &port_lock_key --> &tty->write_wait Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&tty->write_wait); lock(&port_lock_key); lock(&tty->write_wait); lock(&p->pi_lock); *** DEADLOCK *** 7 locks held by kworker/u4:5/4229: #0: ffff888016879138 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1 #1: ffffc900030bfd00 ((work_completion)(&buf->work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285 #2: ffff8880228e88b8 (&buf->lock/1){+.+.}-{3:3}, at: flush_to_ldisc+0x34/0x530 drivers/tty/tty_buffer.c:495 #3: ffff888024ae2098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x18/0x80 drivers/tty/tty_ldisc.c:273 #4: ffff888024ae22e8 (&tty->termios_rwsem/1){++++}-{3:3}, at: n_tty_receive_buf_common+0x8a/0x6480 drivers/tty/n_tty.c:1637 #5: ffff888024ae2250 (&tty->throttle_mutex){+.+.}-{3:3}, at: tty_unthrottle_safe+0x2d/0x160 drivers/tty/tty_ioctl.c:171 #6: ffff88807925e528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up_common_lock kernel/sched/wait.c:137 [inline] #6: ffff88807925e528 (&tty->write_wait){-.-.}-{2:2}, at: __wake_up+0xed/0x180 kernel/sched/wait.c:157 stack backtrace: CPU: 0 PID: 4229 Comm: kworker/u4:5 Not tainted 5.15.184-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Workqueue: events_unbound flush_to_ldisc Call Trace: dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133 check_prev_add kernel/locking/lockdep.c:3053 [inline] check_prevs_add kernel/locking/lockdep.c:3172 [inline] validate_chain kernel/locking/lockdep.c:3788 [inline] __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0xa4/0xf0 kernel/locking/spinlock.c:162 try_to_wake_up+0x5c/0x1050 kernel/sched/core.c:4030 __wake_up_common+0x2a4/0x4e0 kernel/sched/wait.c:108 __wake_up_common_lock kernel/sched/wait.c:138 [inline] __wake_up+0x108/0x180 kernel/sched/wait.c:157 pty_unthrottle+0x38/0x60 drivers/tty/pty.c:95 tty_unthrottle_safe+0x109/0x160 drivers/tty/tty_ioctl.c:178 n_tty_receive_buf_common+0x60db/0x6480 drivers/tty/n_tty.c:1689 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+0x863/0x1000 kernel/workqueue.c:2310 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457 kthread+0x436/0x520 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bridge: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): bridge_slave_0: link becomes ready bridge0: port 1(bridge_slave_0) entered blocking state bridge0: port 1(bridge_slave_0) entered forwarding state IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bridge: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): bridge_slave_1: link becomes ready bridge0: port 2(bridge_slave_1) entered blocking state bridge0: port 2(bridge_slave_1) entered forwarding state IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_bond: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): bridge0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_bond: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_team: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): team_slave_0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): team0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vxcan1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): vxcan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): macvlan0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): macvlan1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth1_macvtap: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth0_macvtap: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): macvtap0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): macsec0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_0: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_batadv: link becomes ready wlan0: Created IBSS using preconfigured BSSID 50:50:50:50:50:50 wlan0: Creating new IBSS network, BSSID 50:50:50:50:50:50