====================================================== WARNING: possible circular locking dependency detected 5.5.0-rc6-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.1/7821 is trying to acquire lock: ffffffff88591b20 (console_owner){-.-.}, at: console_trylock_spinning kernel/printk/printk.c:1724 [inline] ffffffff88591b20 (console_owner){-.-.}, at: vprintk_emit+0x2c7/0x560 kernel/printk/printk.c:1995 but task is already holding lock: ffff8880959c2140 (&(&port->lock)->rlock){-.-.}, at: pty_write+0xbf/0x200 drivers/tty/pty.c:120 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&(&port->lock)->rlock){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:159 tty_port_tty_get+0x1d/0xb0 drivers/tty/tty_port.c:287 tty_port_default_wakeup+0xa/0x30 drivers/tty/tty_port.c:47 tty_port_tty_wakeup+0x53/0x70 drivers/tty/tty_port.c:387 uart_write_wakeup+0x37/0x50 drivers/tty/serial/serial_core.c:104 serial8250_tx_chars+0x3dc/0x9d0 drivers/tty/serial/8250/8250_port.c:1761 serial8250_handle_irq.part.27+0x1e1/0x270 drivers/tty/serial/8250/8250_port.c:1834 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1820 [inline] serial8250_default_handle_irq+0x7c/0xe0 drivers/tty/serial/8250/8250_port.c:1850 serial8250_interrupt+0xcc/0x150 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x120/0x6e0 kernel/irq/handle.c:149 handle_irq_event_percpu+0x6c/0x140 kernel/irq/handle.c:189 handle_irq_event+0xa2/0x130 kernel/irq/handle.c:206 handle_edge_irq+0x206/0x780 kernel/irq/chip.c:830 generic_handle_irq_desc include/linux/irqdesc.h:156 [inline] do_IRQ+0xde/0x280 arch/x86/kernel/irq.c:250 ret_from_intr+0x0/0x36 native_safe_halt+0x12/0x20 arch/x86/include/asm/irqflags.h:60 arch_safe_halt arch/x86/include/asm/paravirt.h:144 [inline] default_idle+0x51/0x340 arch/x86/kernel/process.c:699 arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:690 default_idle_call+0x87/0xa0 kernel/sched/idle.c:94 cpuidle_idle_call kernel/sched/idle.c:154 [inline] do_idle+0x4b5/0x6d0 kernel/sched/idle.c:269 cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:361 start_secondary+0x306/0x3f0 arch/x86/kernel/smpboot.c:264 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242 -> #1 (&port_lock_key){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:159 serial8250_console_write+0x1f0/0x800 drivers/tty/serial/8250/8250_port.c:3142 univ8250_console_write+0x4e/0x70 drivers/tty/serial/8250/8250_core.c:587 call_console_drivers kernel/printk/printk.c:1791 [inline] console_unlock+0x86a/0xbd0 kernel/printk/printk.c:2473 vprintk_emit+0x19a/0x560 kernel/printk/printk.c:1996 vprintk_default+0x1a/0x20 kernel/printk/printk.c:2023 vprintk_func+0x49/0x12c kernel/printk/printk_safe.c:386 printk+0x9a/0xc0 kernel/printk/printk.c:2056 register_console+0x593/0x930 kernel/printk/printk.c:2798 univ8250_console_init+0x1e/0x28 drivers/tty/serial/8250/8250_core.c:682 console_init+0x2ef/0x445 kernel/printk/printk.c:2884 start_kernel+0x4f3/0x766 init/main.c:712 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490 x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:471 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242 -> #0 (console_owner){-.-.}: check_prev_add kernel/locking/lockdep.c:2476 [inline] check_prevs_add kernel/locking/lockdep.c:2581 [inline] validate_chain kernel/locking/lockdep.c:2971 [inline] __lock_acquire+0x2899/0x4ef0 kernel/locking/lockdep.c:3955 lock_acquire+0x194/0x410 kernel/locking/lockdep.c:4485 console_trylock_spinning kernel/printk/printk.c:1745 [inline] vprintk_emit+0x2fa/0x560 kernel/printk/printk.c:1995 vprintk_default+0x1a/0x20 kernel/printk/printk.c:2023 vprintk_func+0x49/0x12c kernel/printk/printk_safe.c:386 printk+0x9a/0xc0 kernel/printk/printk.c:2056 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x551/0x68a lib/fault-inject.c:144 __should_failslab+0xba/0xf0 mm/failslab.c:33 should_failslab+0x9/0x14 mm/slab_common.c:1810 slab_pre_alloc_hook mm/slab.h:567 [inline] slab_alloc mm/slab.c:3306 [inline] __do_kmalloc mm/slab.c:3654 [inline] __kmalloc+0x70/0x790 mm/slab.c:3665 kmalloc include/linux/slab.h:561 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline] __tty_buffer_request_room+0x1b1/0x550 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x77/0x1a0 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0xf3/0x200 drivers/tty/pty.c:122 process_output_block drivers/tty/n_tty.c:595 [inline] n_tty_write+0x494/0xfa0 drivers/tty/n_tty.c:2333 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x371/0x7d0 drivers/tty/tty_io.c:1046 __vfs_write+0x5e/0x110 fs/read_write.c:494 vfs_write+0x18a/0x520 fs/read_write.c:558 ksys_write+0x105/0x220 fs/read_write.c:611 __do_sys_write fs/read_write.c:623 [inline] __se_sys_write fs/read_write.c:620 [inline] __x64_sys_write+0x6e/0xb0 fs/read_write.c:620 do_syscall_64+0xca/0x5f0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: console_owner --> &port_lock_key --> &(&port->lock)->rlock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&(&port->lock)->rlock); lock(&port_lock_key); lock(&(&port->lock)->rlock); lock(console_owner); *** DEADLOCK *** 5 locks held by syz-executor.1/7821: #0: ffff88808e764090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:340 #1: ffff88808e764118 (&tty->atomic_write_lock){+.+.}, at: tty_write_lock+0x19/0x50 drivers/tty/tty_io.c:888 #2: ffff88808e7642a0 (&o_tty->termios_rwsem/1){++++}, at: n_tty_write+0x17e/0xfa0 drivers/tty/n_tty.c:2316 #3: ffffc900060cf360 (&ldata->output_lock){+.+.}, at: process_output_block drivers/tty/n_tty.c:550 [inline] #3: ffffc900060cf360 (&ldata->output_lock){+.+.}, at: n_tty_write+0x30d/0xfa0 drivers/tty/n_tty.c:2333 #4: ffff8880959c2140 (&(&port->lock)->rlock){-.-.}, at: pty_write+0xbf/0x200 drivers/tty/pty.c:120 stack backtrace: CPU: 0 PID: 7821 Comm: syz-executor.1 Not tainted 5.5.0-rc6-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+0x12d/0x187 lib/dump_stack.c:118 print_circular_bug.isra.39.cold.58+0x15a/0x169 kernel/locking/lockdep.c:1685 check_noncircular+0x349/0x400 kernel/locking/lockdep.c:1809 check_prev_add kernel/locking/lockdep.c:2476 [inline] check_prevs_add kernel/locking/lockdep.c:2581 [inline] validate_chain kernel/locking/lockdep.c:2971 [inline] __lock_acquire+0x2899/0x4ef0 kernel/locking/lockdep.c:3955 lock_acquire+0x194/0x410 kernel/locking/lockdep.c:4485 console_trylock_spinning kernel/printk/printk.c:1745 [inline] vprintk_emit+0x2fa/0x560 kernel/printk/printk.c:1995 vprintk_default+0x1a/0x20 kernel/printk/printk.c:2023 vprintk_func+0x49/0x12c kernel/printk/printk_safe.c:386 printk+0x9a/0xc0 kernel/printk/printk.c:2056 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x551/0x68a lib/fault-inject.c:144 __should_failslab+0xba/0xf0 mm/failslab.c:33 should_failslab+0x9/0x14 mm/slab_common.c:1810 slab_pre_alloc_hook mm/slab.h:567 [inline] slab_alloc mm/slab.c:3306 [inline] __do_kmalloc mm/slab.c:3654 [inline] __kmalloc+0x70/0x790 mm/slab.c:3665 kmalloc include/linux/slab.h:561 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline] __tty_buffer_request_room+0x1b1/0x550 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x77/0x1a0 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0xf3/0x200 drivers/tty/pty.c:122 process_output_block drivers/tty/n_tty.c:595 [inline] n_tty_write+0x494/0xfa0 drivers/tty/n_tty.c:2333 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x371/0x7d0 drivers/tty/tty_io.c:1046 __vfs_write+0x5e/0x110 fs/read_write.c:494 vfs_write+0x18a/0x520 fs/read_write.c:558 ksys_write+0x105/0x220 fs/read_write.c:611 __do_sys_write fs/read_write.c:623 [inline] __se_sys_write fs/read_write.c:620 [inline] __x64_sys_write+0x6e/0xb0 fs/read_write.c:620 do_syscall_64+0xca/0x5f0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4592c9 Code: fd b7 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 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f724fbf8c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f724fbf8c90 RCX: 00000000004592c9 RDX: 00000000ffffff86 RSI: 0000000020000000 RDI: 0000000000000005 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f724fbf96d4 R13: 00000000004c566b R14: 00000000004df350 R15: 0000000000000006