workqueue: work func io_tctx_fallback_work enqueued on deprecated workqueue. Use system_{percpu|dfl}_wq instead. ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.6/5740 is trying to acquire lock: ffffffff8e94bf00 (console_owner){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:305 [inline] ffffffff8e94bf00 (console_owner){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:428 [inline] ffffffff8e94bf00 (console_owner){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:291 [inline] ffffffff8e94bf00 (console_owner){....}-{0:0}, at: console_flush_one_record kernel/printk/printk.c:3246 [inline] ffffffff8e94bf00 (console_owner){....}-{0:0}, at: console_flush_all+0x123/0xaf0 kernel/printk/printk.c:3343 but task is already holding lock: ffff88802608a4f8 (&tty->write_wait){-.-.}-{3:3}, at: __wake_up_common_lock+0x30/0x1f0 kernel/sched/wait.c:124 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&tty->write_wait){-.-.}-{3:3}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline] _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:166 __wake_up_common_lock+0x30/0x1f0 kernel/sched/wait.c:124 tty_port_default_wakeup+0xc8/0x100 drivers/tty/tty_port.c:67 serial8250_tx_chars+0x70e/0x950 drivers/tty/serial/8250/8250_port.c:1723 serial8250_handle_irq+0x166/0x550 drivers/tty/serial/8250/8250_port.c:1853 serial8250_default_handle_irq+0xbf/0x1e0 drivers/tty/serial/8250/8250_port.c:1867 serial8250_interrupt+0x8d/0x160 drivers/tty/serial/8250/8250_core.c:86 __handle_irq_event_percpu+0x216/0x9a0 kernel/irq/handle.c:209 handle_irq_event_percpu kernel/irq/handle.c:246 [inline] handle_irq_event+0x8b/0x1e0 kernel/irq/handle.c:263 handle_edge_irq+0x1f4/0x8a0 kernel/irq/chip.c:859 generic_handle_irq_desc include/linux/irqdesc.h:188 [inline] handle_irq arch/x86/kernel/irq.c:209 [inline] call_irq_handler arch/x86/kernel/irq.c:-1 [inline] __common_interrupt+0x141/0x1f0 arch/x86/kernel/irq.c:280 common_interrupt+0xb6/0xe0 arch/x86/kernel/irq.c:273 asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:665 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:179 [inline] _raw_spin_unlock_irqrestore+0x47/0x80 kernel/locking/spinlock.c:198 spin_unlock_irqrestore include/linux/spinlock.h:408 [inline] uart_port_unlock_irqrestore include/linux/serial_core.h:790 [inline] uart_port_unlock_deref drivers/tty/serial/serial_core.c:91 [inline] uart_write+0x3c0/0x9f0 drivers/tty/serial/serial_core.c:630 process_output_block drivers/tty/n_tty.c:557 [inline] n_tty_write+0xd49/0x11e0 drivers/tty/n_tty.c:2366 iterate_tty_write drivers/tty/tty_io.c:1006 [inline] file_tty_write+0x509/0x9c0 drivers/tty/tty_io.c:1081 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x612/0xba0 fs/read_write.c:687 ksys_write+0x150/0x270 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&port_lock_key){-.-.}-{3:3}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline] _raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:166 uart_port_lock_irqsave include/linux/serial_core.h:719 [inline] serial8250_console_write+0x153/0x1ba0 drivers/tty/serial/8250/8250_port.c:3338 console_emit_next_record kernel/printk/printk.c:3183 [inline] console_flush_one_record kernel/printk/printk.c:3269 [inline] console_flush_all+0x6ea/0xaf0 kernel/printk/printk.c:3343 __console_flush_and_unlock kernel/printk/printk.c:3373 [inline] console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413 vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479 _printk+0xdd/0x130 kernel/printk/printk.c:2504 register_console+0xbc3/0xfc0 kernel/printk/printk.c:4208 univ8250_console_init+0x3a/0x70 drivers/tty/serial/8250/8250_core.c:515 console_init+0x10b/0x4a0 kernel/printk/printk.c:4407 start_kernel+0x238/0x3e0 init/main.c:1112 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310 x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291 common_startup_64+0x13e/0x157 -> #0 (console_owner){....}-{0:0}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 console_lock_spinning_enable kernel/printk/printk.c:1902 [inline] console_emit_next_record kernel/printk/printk.c:3177 [inline] console_flush_one_record kernel/printk/printk.c:3269 [inline] console_flush_all+0x693/0xaf0 kernel/printk/printk.c:3343 __console_flush_and_unlock kernel/printk/printk.c:3373 [inline] console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413 vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479 _printk+0xdd/0x130 kernel/printk/printk.c:2504 __queue_work+0xf63/0x10a0 kernel/workqueue.c:2287 queue_work_on+0x106/0x1d0 kernel/workqueue.c:2452 queue_work include/linux/workqueue.h:699 [inline] io_fallback_tw+0xc9/0x1b0 io_uring/tw.c:58 io_poll_wake+0x373/0x460 io_uring/poll.c:433 __wake_up_common kernel/sched/wait.c:108 [inline] __wake_up_common_lock+0x13a/0x1f0 kernel/sched/wait.c:125 n_hdlc_send_frames+0x53e/0xa40 drivers/tty/n_hdlc.c:299 n_hdlc_tty_write+0x7c2/0x960 drivers/tty/n_hdlc.c:558 iterate_tty_write drivers/tty/tty_io.c:1006 [inline] file_tty_write+0x509/0x9c0 drivers/tty/tty_io.c:1081 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x612/0xba0 fs/read_write.c:687 ksys_write+0x150/0x270 fs/read_write.c:739 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0x23e/0x6f0 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332 entry_SYSENTER_compat_after_hwframe+0x84/0x8e other info that might help us debug this: Chain exists of: console_owner --> &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(console_owner); *** DEADLOCK *** 5 locks held by syz.0.6/5740: #0: ffff88802608a0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243 #1: ffff88802608a128 (&tty->atomic_write_lock){+.+.}-{4:4}, at: tty_write_lock drivers/tty/tty_io.c:939 [inline] #1: ffff88802608a128 (&tty->atomic_write_lock){+.+.}-{4:4}, at: iterate_tty_write drivers/tty/tty_io.c:958 [inline] #1: ffff88802608a128 (&tty->atomic_write_lock){+.+.}-{4:4}, at: file_tty_write+0x1e4/0x9c0 drivers/tty/tty_io.c:1081 #2: ffff88802608a4f8 (&tty->write_wait){-.-.}-{3:3}, at: __wake_up_common_lock+0x30/0x1f0 kernel/sched/wait.c:124 #3: ffffffff8e94bf60 (console_lock){+.+.}-{0:0}, at: _printk+0xdd/0x130 kernel/printk/printk.c:2504 #4: ffffffff8e8337f8 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:305 [inline] #4: ffffffff8e8337f8 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:428 [inline] #4: ffffffff8e8337f8 (console_srcu){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:291 [inline] #4: ffffffff8e8337f8 (console_srcu){....}-{0:0}, at: console_flush_one_record kernel/printk/printk.c:3246 [inline] #4: ffffffff8e8337f8 (console_srcu){....}-{0:0}, at: console_flush_all+0x123/0xaf0 kernel/printk/printk.c:3343 stack backtrace: CPU: 1 UID: 0 PID: 5740 Comm: syz.0.6 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 console_lock_spinning_enable kernel/printk/printk.c:1902 [inline] console_emit_next_record kernel/printk/printk.c:3177 [inline] console_flush_one_record kernel/printk/printk.c:3269 [inline] console_flush_all+0x693/0xaf0 kernel/printk/printk.c:3343 __console_flush_and_unlock kernel/printk/printk.c:3373 [inline] console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413 vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479 _printk+0xdd/0x130 kernel/printk/printk.c:2504 __queue_work+0xf63/0x10a0 kernel/workqueue.c:2287 queue_work_on+0x106/0x1d0 kernel/workqueue.c:2452 queue_work include/linux/workqueue.h:699 [inline] io_fallback_tw+0xc9/0x1b0 io_uring/tw.c:58 io_poll_wake+0x373/0x460 io_uring/poll.c:433 __wake_up_common kernel/sched/wait.c:108 [inline] __wake_up_common_lock+0x13a/0x1f0 kernel/sched/wait.c:125 n_hdlc_send_frames+0x53e/0xa40 drivers/tty/n_hdlc.c:299 n_hdlc_tty_write+0x7c2/0x960 drivers/tty/n_hdlc.c:558 iterate_tty_write drivers/tty/tty_io.c:1006 [inline] file_tty_write+0x509/0x9c0 drivers/tty/tty_io.c:1081 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x612/0xba0 fs/read_write.c:687 ksys_write+0x150/0x270 fs/read_write.c:739 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline] __do_fast_syscall_32+0x23e/0x6f0 arch/x86/entry/syscall_32.c:307 do_fast_syscall_32+0x33/0x70 arch/x86/entry/syscall_32.c:332 entry_SYSENTER_compat_after_hwframe+0x84/0x8e RIP: 0023:0xf7f990ec Code: 90 85 d2 74 0a 89 ce 81 e6 ff 0f 00 00 89 32 85 c0 74 05 c1 e9 0c 89 08 31 c0 5e 5d c3 90 0f 1f 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 58 b8 RSP: 002b:00000000f545650c EFLAGS: 00000206 ORIG_RAX: 0000000000000004 RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000080001040 RDX: 00000000fffffdef RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 ---------------- Code disassembly (best guess): 0: 90 nop 1: 85 d2 test %edx,%edx 3: 74 0a je 0xf 5: 89 ce mov %ecx,%esi 7: 81 e6 ff 0f 00 00 and $0xfff,%esi d: 89 32 mov %esi,(%rdx) f: 85 c0 test %eax,%eax 11: 74 05 je 0x18 13: c1 e9 0c shr $0xc,%ecx 16: 89 08 mov %ecx,(%rax) 18: 31 c0 xor %eax,%eax 1a: 5e pop %rsi 1b: 5d pop %rbp 1c: c3 ret 1d: 90 nop 1e: 0f 1f 00 nopl (%rax) 21: 51 push %rcx 22: 52 push %rdx 23: 55 push %rbp 24: 89 e5 mov %esp,%ebp 26: 0f 34 sysenter 28: cd 80 int $0x80 * 2a: 5d pop %rbp <-- trapping instruction 2b: 5a pop %rdx 2c: 59 pop %rcx 2d: c3 ret 2e: 90 nop 2f: 90 nop 30: 90 nop 31: 90 nop 32: 90 nop 33: 90 nop 34: 90 nop 35: 90 nop 36: 90 nop 37: 90 nop 38: 90 nop 39: 90 nop 3a: 90 nop 3b: 90 nop 3c: 90 nop 3d: 90 nop 3e: 58 pop %rax 3f: b8 .byte 0xb8