RBP: 00000000006cb018 R08: 0000000000000001 R09: 0000000000000031 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004 R13: ffffffffffffffff R14: 0000000000000000 R15: 0000000000000000 ====================================================== WARNING: possible circular locking dependency detected 4.20.0+ #1 Not tainted ------------------------------------------------------ syz-executor066/8359 is trying to acquire lock: 00000000caabada3 (console_owner){-.-.}, at: console_trylock_spinning kernel/printk/printk.c:1670 [inline] 00000000caabada3 (console_owner){-.-.}, at: vprintk_emit+0x54f/0x960 kernel/printk/printk.c:1930 but task is already holding lock: 00000000da6a7ef7 (&(&port->lock)->rlock){-.-.}, at: pty_write+0xff/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+0x95/0xcd kernel/locking/spinlock.c:152 tty_port_tty_get+0x22/0x80 drivers/tty/tty_port.c:287 tty_port_default_wakeup+0x16/0x40 drivers/tty/tty_port.c:47 tty_port_tty_wakeup+0x5d/0x70 drivers/tty/tty_port.c:387 uart_write_wakeup+0x46/0x70 drivers/tty/serial/serial_core.c:103 serial8250_tx_chars+0x4a4/0xb20 drivers/tty/serial/8250/8250_port.c:1806 serial8250_handle_irq.part.0+0x1be/0x2e0 drivers/tty/serial/8250/8250_port.c:1879 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1865 [inline] serial8250_default_handle_irq+0xc5/0x150 drivers/tty/serial/8250/8250_port.c:1895 serial8250_interrupt+0xfb/0x1a0 drivers/tty/serial/8250/8250_core.c:125 __handle_irq_event_percpu+0x1c6/0xb10 kernel/irq/handle.c:149 handle_irq_event_percpu+0xa0/0x1d0 kernel/irq/handle.c:189 handle_irq_event+0xa7/0x134 kernel/irq/handle.c:206 handle_edge_irq+0x232/0x8a0 kernel/irq/chip.c:791 generic_handle_irq_desc include/linux/irqdesc.h:154 [inline] handle_irq+0x252/0x3d8 arch/x86/kernel/irq_64.c:78 do_IRQ+0x99/0x1d0 arch/x86/kernel/irq.c:246 ret_from_intr+0x0/0x1e native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:57 arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:555 default_idle_call+0x36/0x90 kernel/sched/idle.c:93 cpuidle_idle_call kernel/sched/idle.c:153 [inline] do_idle+0x386/0x5d0 kernel/sched/idle.c:262 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:353 start_secondary+0x435/0x620 arch/x86/kernel/smpboot.c:271 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 -> #1 (&port_lock_key){-.-.}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152 serial8250_console_write+0x253/0xab0 drivers/tty/serial/8250/8250_port.c:3245 univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:586 call_console_drivers kernel/printk/printk.c:1737 [inline] console_unlock+0xcff/0x11e0 kernel/printk/printk.c:2408 vprintk_emit+0x370/0x960 kernel/printk/printk.c:1931 vprintk_default+0x28/0x30 kernel/printk/printk.c:1958 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398 printk+0xba/0xed kernel/printk/printk.c:1991 register_console+0x74d/0xb50 kernel/printk/printk.c:2723 univ8250_console_init+0x3e/0x4b drivers/tty/serial/8250/8250_core.c:681 console_init+0x6b7/0x9fe kernel/printk/printk.c:2809 start_kernel+0x5df/0x8bd init/main.c:668 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470 x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 -> #0 (console_owner){-.-.}: lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841 console_trylock_spinning kernel/printk/printk.c:1691 [inline] vprintk_emit+0x5a5/0x960 kernel/printk/printk.c:1930 vprintk_default+0x28/0x30 kernel/printk/printk.c:1958 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398 printk+0xba/0xed kernel/printk/printk.c:1991 fail_dump lib/fault-inject.c:44 [inline] should_fail+0xa59/0xd22 lib/fault-inject.c:149 __should_failslab+0x121/0x190 mm/failslab.c:32 should_failslab+0x9/0x14 mm/slab_common.c:1603 slab_pre_alloc_hook mm/slab.h:423 [inline] slab_alloc mm/slab.c:3365 [inline] __do_kmalloc mm/slab.c:3707 [inline] __kmalloc+0x71/0x740 mm/slab.c:3718 kmalloc include/linux/slab.h:550 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline] __tty_buffer_request_room+0x2bf/0x7e0 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x93/0x1f0 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0x133/0x200 drivers/tty/pty.c:122 tty_send_xchar+0x28c/0x390 drivers/tty/tty_io.c:1092 n_tty_ioctl_helper drivers/tty/tty_ioctl.c:927 [inline] n_tty_ioctl_helper+0x192/0x3b0 drivers/tty/tty_ioctl.c:894 n_tty_ioctl+0x59/0x360 drivers/tty/n_tty.c:2464 tty_ioctl+0xb53/0x16c0 drivers/tty/tty_io.c:2655 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:509 [inline] do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713 __do_sys_ioctl fs/ioctl.c:720 [inline] __se_sys_ioctl fs/ioctl.c:718 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 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 *** 4 locks held by syz-executor066/8359: #0: 0000000094bc7f36 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:341 #1: 00000000b7f0e8a5 (&tty->atomic_write_lock){+.+.}, at: tty_write_lock+0x23/0x90 drivers/tty/tty_io.c:885 #2: 00000000527f1cff (&tty->termios_rwsem){++++}, at: tty_send_xchar+0x224/0x390 drivers/tty/tty_io.c:1089 #3: 00000000da6a7ef7 (&(&port->lock)->rlock){-.-.}, at: pty_write+0xff/0x200 drivers/tty/pty.c:120 stack backtrace: CPU: 0 PID: 8359 Comm: syz-executor066 Not tainted 4.20.0+ #1 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+0x1db/0x2d0 lib/dump_stack.c:113 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1224 check_prev_add kernel/locking/lockdep.c:1866 [inline] check_prevs_add kernel/locking/lockdep.c:1979 [inline] validate_chain kernel/locking/lockdep.c:2350 [inline] __lock_acquire+0x3014/0x4a30 kernel/locking/lockdep.c:3338 lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841 console_trylock_spinning kernel/printk/printk.c:1691 [inline] vprintk_emit+0x5a5/0x960 kernel/printk/printk.c:1930 vprintk_default+0x28/0x30 kernel/printk/printk.c:1958 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398 printk+0xba/0xed kernel/printk/printk.c:1991 fail_dump lib/fault-inject.c:44 [inline] should_fail+0xa59/0xd22 lib/fault-inject.c:149 __should_failslab+0x121/0x190 mm/failslab.c:32 should_failslab+0x9/0x14 mm/slab_common.c:1603 slab_pre_alloc_hook mm/slab.h:423 [inline] slab_alloc mm/slab.c:3365 [inline] __do_kmalloc mm/slab.c:3707 [inline] __kmalloc+0x71/0x740 mm/slab.c:3718 kmalloc include/linux/slab.h:550 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline] __tty_buffer_request_room+0x2bf/0x7e0 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x93/0x1f0 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0x133/0x200 drivers/tty/pty.c:122 tty_send_xchar+0x28c/0x390 drivers/tty/tty_io.c:1092 n_tty_ioctl_helper drivers/tty/tty_ioctl.c:927 [inline] n_tty_ioctl_helper+0x192/0x3b0 drivers/tty/tty_ioctl.c:894 n_tty_ioctl+0x59/0x360 drivers/tty/n_tty.c:2464 tty_ioctl+0xb53/0x16c0 drivers/tty/tty_io.c:2655 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:509 [inline] do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696 ksys_ioctl+0xab/0xd0 fs/ioctl.c:713 __do_sys_ioctl fs/ioctl.c:720 [inline] __se_sys_ioctl fs/ioctl.c:718 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4402e9 Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 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 5b 14 fc ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffee51fffe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004402e9 RDX: 0000000000000003 RSI: 000000000000540a RDI: 0000000000000003 RBP: 00000000006cb018 R08: 0000000000000001 R09: 0000000000000031 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004 R13: ffffffffffffffff R