====================================================== WARNING: possible circular locking dependency detected 5.9.0-rc1-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.0/14460 is trying to acquire lock: ffffffff894fc6e0 (console_owner){-.-.}-{0:0}, at: console_trylock_spinning+0x11a/0x380 kernel/printk/printk.c:1764 but task is already holding lock: ffff8880a7d4c958 (&port->lock#2){-.-.}-{2:2}, at: pty_write+0xb6/0x180 drivers/tty/pty.c:120 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&port->lock#2){-.-.}-{2:2}: lock_acquire+0x160/0x730 kernel/locking/lockdep.c:5005 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x9e/0xc0 kernel/locking/spinlock.c:159 tty_port_tty_get+0x21/0xe0 drivers/tty/tty_port.c:288 tty_port_default_wakeup+0x11/0x40 drivers/tty/tty_port.c:47 serial8250_tx_chars+0x5ea/0x800 drivers/tty/serial/8250/8250_port.c:1832 serial8250_handle_irq+0x2fd/0x3e0 drivers/tty/serial/8250/8250_port.c:1919 serial8250_default_handle_irq+0xac/0x190 drivers/tty/serial/8250/8250_port.c:1935 serial8250_interrupt+0x93/0x180 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x1b7/0x610 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xbd/0x280 kernel/irq/handle.c:213 handle_edge_irq+0x245/0xbf0 kernel/irq/chip.c:819 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline] handle_irq arch/x86/kernel/irq.c:230 [inline] __common_interrupt arch/x86/kernel/irq.c:249 [inline] common_interrupt+0x13c/0x230 arch/x86/kernel/irq.c:239 asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:572 native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60 arch_safe_halt arch/x86/include/asm/paravirt.h:150 [inline] acpi_safe_halt+0x87/0xe0 drivers/acpi/processor_idle.c:111 acpi_idle_do_entry drivers/acpi/processor_idle.c:524 [inline] acpi_idle_enter+0x3ef/0xac0 drivers/acpi/processor_idle.c:650 cpuidle_enter_state+0x2d7/0x7b0 drivers/cpuidle/cpuidle.c:235 cpuidle_enter+0x59/0x90 drivers/cpuidle/cpuidle.c:346 call_cpuidle kernel/sched/idle.c:126 [inline] cpuidle_idle_call kernel/sched/idle.c:214 [inline] do_idle+0x49c/0x650 kernel/sched/idle.c:276 cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:372 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 -> #1 (&port->lock){-.-.}-{2:2}: lock_acquire+0x160/0x730 kernel/locking/lockdep.c:5005 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x9e/0xc0 kernel/locking/spinlock.c:159 serial8250_console_write+0x13e/0xd60 drivers/tty/serial/8250/8250_port.c:3286 call_console_drivers kernel/printk/printk.c:1822 [inline] console_unlock+0x90c/0xec0 kernel/printk/printk.c:2501 vprintk_emit+0x1f8/0x3c0 kernel/printk/printk.c:2029 printk+0x62/0x83 kernel/printk/printk.c:2078 register_console+0x7ca/0xad0 kernel/printk/printk.c:2854 univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:690 console_init+0x52/0x97 kernel/printk/printk.c:2954 start_kernel+0x2db/0x4f0 init/main.c:975 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 -> #0 (console_owner){-.-.}-{0:0}: check_prev_add kernel/locking/lockdep.c:2496 [inline] check_prevs_add kernel/locking/lockdep.c:2601 [inline] validate_chain+0x1b0c/0x88a0 kernel/locking/lockdep.c:3218 __lock_acquire+0x1161/0x2ab0 kernel/locking/lockdep.c:4426 lock_acquire+0x160/0x730 kernel/locking/lockdep.c:5005 console_trylock_spinning+0x13a/0x380 kernel/printk/printk.c:1781 vprintk_emit+0x1db/0x3c0 kernel/printk/printk.c:2028 printk+0x62/0x83 kernel/printk/printk.c:2078 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x36c/0x4e0 lib/fault-inject.c:146 should_failslab+0x5/0x20 mm/slab_common.c:1194 slab_pre_alloc_hook+0x4c/0xe0 mm/slab.h:500 slab_alloc mm/slab.c:3298 [inline] __do_kmalloc mm/slab.c:3653 [inline] __kmalloc+0x6c/0x320 mm/slab.c:3664 kmalloc include/linux/slab.h:559 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline] __tty_buffer_request_room+0x1f3/0x540 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x91/0x2c0 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0xda/0x180 drivers/tty/pty.c:122 tty_put_char+0xc7/0x110 drivers/tty/tty_io.c:3032 __process_echoes+0x45e/0x930 drivers/tty/n_tty.c:728 flush_echoes drivers/tty/n_tty.c:829 [inline] __receive_buf drivers/tty/n_tty.c:1648 [inline] n_tty_receive_buf_common+0x29fa/0x3100 drivers/tty/n_tty.c:1742 tiocsti drivers/tty/tty_io.c:2196 [inline] tty_ioctl+0xd5b/0x15c0 drivers/tty/tty_io.c:2572 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 other info that might help us debug this: Chain exists of: console_owner --> &port->lock --> &port->lock#2 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&port->lock#2); lock(&port->lock); lock(&port->lock#2); lock(console_owner); *** DEADLOCK *** 4 locks held by syz-executor.0/14460: #0: ffff8880a8017098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:267 #1: ffff8880a80172e8 (&o_tty->termios_rwsem/1){++++}-{3:3}, at: n_tty_receive_signal_char drivers/tty/n_tty.c:1243 [inline] #1: ffff8880a80172e8 (&o_tty->termios_rwsem/1){++++}-{3:3}, at: n_tty_receive_char_special+0x2e3/0x5f30 drivers/tty/n_tty.c:1289 #2: ffffc90008b6b378 (&ldata->output_lock){+.+.}-{3:3}, at: flush_echoes drivers/tty/n_tty.c:827 [inline] #2: ffffc90008b6b378 (&ldata->output_lock){+.+.}-{3:3}, at: __receive_buf drivers/tty/n_tty.c:1648 [inline] #2: ffffc90008b6b378 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_receive_buf_common+0x29bb/0x3100 drivers/tty/n_tty.c:1742 #3: ffff8880a7d4c958 (&port->lock#2){-.-.}-{2:2}, at: pty_write+0xb6/0x180 drivers/tty/pty.c:120 stack backtrace: CPU: 0 PID: 14460 Comm: syz-executor.0 Not tainted 5.9.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x1f0/0x31e lib/dump_stack.c:118 print_circular_bug+0xc72/0xea0 kernel/locking/lockdep.c:1703 check_noncircular+0x1fb/0x3a0 kernel/locking/lockdep.c:1827 check_prev_add kernel/locking/lockdep.c:2496 [inline] check_prevs_add kernel/locking/lockdep.c:2601 [inline] validate_chain+0x1b0c/0x88a0 kernel/locking/lockdep.c:3218 __lock_acquire+0x1161/0x2ab0 kernel/locking/lockdep.c:4426 lock_acquire+0x160/0x730 kernel/locking/lockdep.c:5005 console_trylock_spinning+0x13a/0x380 kernel/printk/printk.c:1781 vprintk_emit+0x1db/0x3c0 kernel/printk/printk.c:2028 printk+0x62/0x83 kernel/printk/printk.c:2078 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x36c/0x4e0 lib/fault-inject.c:146 should_failslab+0x5/0x20 mm/slab_common.c:1194 slab_pre_alloc_hook+0x4c/0xe0 mm/slab.h:500 slab_alloc mm/slab.c:3298 [inline] __do_kmalloc mm/slab.c:3653 [inline] __kmalloc+0x6c/0x320 mm/slab.c:3664 kmalloc include/linux/slab.h:559 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline] __tty_buffer_request_room+0x1f3/0x540 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x91/0x2c0 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0xda/0x180 drivers/tty/pty.c:122 tty_put_char+0xc7/0x110 drivers/tty/tty_io.c:3032 __process_echoes+0x45e/0x930 drivers/tty/n_tty.c:728 flush_echoes drivers/tty/n_tty.c:829 [inline] __receive_buf drivers/tty/n_tty.c:1648 [inline] n_tty_receive_buf_common+0x29fa/0x3100 drivers/tty/n_tty.c:1742 tiocsti drivers/tty/tty_io.c:2196 [inline] tty_ioctl+0xd5b/0x15c0 drivers/tty/tty_io.c:2572 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45d4d9 Code: 5d b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f0b9b9a1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000017cc0 RCX: 000000000045d4d9 RDX: 0000000020000000 RSI: 0000000000005412 RDI: 0000000000000004 RBP: 00007f0b9b9a1ca0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003 R13: 00007ffd4602c54f R14: 00007f0b9b9a29c0 R15: 000000000118cf4c