====================================================== WARNING: possible circular locking dependency detected 5.9.0-rc1-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.2/8223 is trying to acquire lock: ffffffff89fb5260 (console_owner){-.-.}-{0:0}, at: log_next kernel/printk/printk.c:528 [inline] ffffffff89fb5260 (console_owner){-.-.}-{0:0}, at: console_unlock+0x418/0xf40 kernel/printk/printk.c:2488 but task is already holding lock: ffff88809ef19958 (&port->lock#2){-.-.}-{2:2}, 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#2){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xd0 kernel/locking/spinlock.c:159 tty_port_tty_get+0x24/0x100 drivers/tty/tty_port.c:288 tty_port_default_wakeup+0x16/0x40 drivers/tty/tty_port.c:47 tty_port_tty_wakeup+0x57/0x70 drivers/tty/tty_port.c:388 uart_write_wakeup+0x46/0x60 drivers/tty/serial/serial_core.c:106 serial8250_tx_chars+0x48d/0xaa0 drivers/tty/serial/8250/8250_port.c:1832 serial8250_handle_irq.part.0+0x345/0x3f0 drivers/tty/serial/8250/8250_port.c:1919 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1892 [inline] serial8250_default_handle_irq+0xbd/0x230 drivers/tty/serial/8250/8250_port.c:1935 serial8250_interrupt+0xf1/0x1a0 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x220/0xa30 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0x10f/0x2a0 kernel/irq/handle.c:213 handle_edge_irq+0x262/0xd10 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+0x124/0x200 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 acpi_idle_do_entry+0x16a/0x1d0 drivers/acpi/processor_idle.c:524 acpi_idle_enter+0x434/0xb20 drivers/acpi/processor_idle.c:650 cpuidle_enter_state+0x10b/0x990 drivers/cpuidle/cpuidle.c:235 cpuidle_enter+0x4f/0xa0 drivers/cpuidle/cpuidle.c:346 call_cpuidle kernel/sched/idle.c:126 [inline] cpuidle_idle_call kernel/sched/idle.c:214 [inline] do_idle+0x494/0x770 kernel/sched/idle.c:276 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:372 start_secondary+0x1f8/0x270 arch/x86/kernel/smpboot.c:266 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243 -> #1 (&port->lock){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x95/0xd0 kernel/locking/spinlock.c:159 serial8250_console_write+0x220/0xc30 drivers/tty/serial/8250/8250_port.c:3286 univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:586 call_console_drivers kernel/printk/printk.c:1824 [inline] console_unlock+0xb03/0xf40 kernel/printk/printk.c:2501 vprintk_emit+0x2f6/0x760 kernel/printk/printk.c:2029 vprintk_default+0x28/0x30 kernel/printk/printk.c:2047 vprintk_func+0x94/0x1ad kernel/printk/printk_safe.c:393 printk+0xba/0xed kernel/printk/printk.c:2078 register_console kernel/printk/printk.c:2854 [inline] register_console+0x567/0x7f0 kernel/printk/printk.c:2733 univ8250_console_init+0x3e/0x4b drivers/tty/serial/8250/8250_core.c:690 console_init+0x443/0x64e kernel/printk/printk.c:2954 start_kernel+0x2d5/0x469 init/main.c:975 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490 x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:471 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 kernel/locking/lockdep.c:3218 [inline] __lock_acquire+0x2cdc/0x5bc0 kernel/locking/lockdep.c:4426 lock_acquire+0x208/0xb70 kernel/locking/lockdep.c:5005 console_lock_spinning_enable kernel/printk/printk.c:1690 [inline] console_unlock+0x482/0xf40 kernel/printk/printk.c:2498 vprintk_emit+0x2f6/0x760 kernel/printk/printk.c:2029 vprintk_default+0x28/0x30 kernel/printk/printk.c:2047 vprintk_func+0x94/0x1ad kernel/printk/printk_safe.c:393 printk+0xba/0xed kernel/printk/printk.c:2078 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x477/0x5a0 lib/fault-inject.c:146 __should_failslab+0xb7/0x100 mm/failslab.c:33 should_failslab+0x9/0x14 mm/slab_common.c:1194 slab_pre_alloc_hook.constprop.0+0x46/0x200 mm/slab.h:500 slab_alloc mm/slab.c:3298 [inline] __do_kmalloc mm/slab.c:3653 [inline] __kmalloc+0x70/0x310 mm/slab.c:3664 kmalloc include/linux/slab.h:559 [inline] tty_buffer_alloc+0x247/0x2b0 drivers/tty/tty_buffer.c:175 __tty_buffer_request_room+0x162/0x2d0 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x93/0x240 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 n_tty_write+0xb69/0x10e0 drivers/tty/n_tty.c:2356 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x4df/0x850 drivers/tty/tty_io.c:1046 do_loop_readv_writev fs/read_write.c:737 [inline] do_loop_readv_writev fs/read_write.c:721 [inline] do_iter_write+0x4af/0x690 fs/read_write.c:1020 vfs_writev+0x1c5/0x310 fs/read_write.c:1091 do_writev+0x161/0x340 fs/read_write.c:1134 __do_sys_writev fs/read_write.c:1207 [inline] __se_sys_writev fs/read_write.c:1204 [inline] __x64_sys_writev+0x75/0xb0 fs/read_write.c:1204 do_syscall_64+0x32/0x80 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 *** 6 locks held by syz-executor.2/8223: #0: ffff8880a1f26098 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffff8880a1f26130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:888 [inline] #1: ffff8880a1f26130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: do_tty_write drivers/tty/tty_io.c:911 [inline] #1: ffff8880a1f26130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write+0x28f/0x850 drivers/tty/tty_io.c:1046 #2: ffff8880a1f262e8 (&tty->termios_rwsem){++++}-{3:3}, at: n_tty_write+0x1ab/0x10e0 drivers/tty/n_tty.c:2316 #3: ffffc90000f62378 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_write+0xb29/0x10e0 drivers/tty/n_tty.c:2355 #4: ffff88809ef19958 (&port->lock#2){-.-.}-{2:2}, at: pty_write+0xff/0x200 drivers/tty/pty.c:120 #5: ffffffff89fb54e0 (console_lock){+.+.}-{0:0}, at: vprintk_default+0x28/0x30 kernel/printk/printk.c:2047 stack backtrace: CPU: 1 PID: 8223 Comm: syz-executor.2 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+0x19e/0x21e lib/dump_stack.c:118 print_circular_bug.cold+0x162/0x171 kernel/locking/lockdep.c:1703 check_noncircular+0x35f/0x450 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 kernel/locking/lockdep.c:3218 [inline] __lock_acquire+0x2cdc/0x5bc0 kernel/locking/lockdep.c:4426 lock_acquire+0x208/0xb70 kernel/locking/lockdep.c:5005 console_lock_spinning_enable kernel/printk/printk.c:1690 [inline] console_unlock+0x482/0xf40 kernel/printk/printk.c:2498 vprintk_emit+0x2f6/0x760 kernel/printk/printk.c:2029 vprintk_default+0x28/0x30 kernel/printk/printk.c:2047 vprintk_func+0x94/0x1ad kernel/printk/printk_safe.c:393 printk+0xba/0xed kernel/printk/printk.c:2078 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x477/0x5a0 lib/fault-inject.c:146 __should_failslab+0xb7/0x100 mm/failslab.c:33 should_failslab+0x9/0x14 mm/slab_common.c:1194 slab_pre_alloc_hook.constprop.0+0x46/0x200 mm/slab.h:500 slab_alloc mm/slab.c:3298 [inline] __do_kmalloc mm/slab.c:3653 [inline] __kmalloc+0x70/0x310 mm/slab.c:3664 kmalloc include/linux/slab.h:559 [inline] tty_buffer_alloc+0x247/0x2b0 drivers/tty/tty_buffer.c:175 __tty_buffer_request_room+0x162/0x2d0 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x93/0x240 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 n_tty_write+0xb69/0x10e0 drivers/tty/n_tty.c:2356 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x4df/0x850 drivers/tty/tty_io.c:1046 do_loop_readv_writev fs/read_write.c:737 [inline] do_loop_readv_writev fs/read_write.c:721 [inline] do_iter_write+0x4af/0x690 fs/read_write.c:1020 vfs_writev+0x1c5/0x310 fs/read_write.c:1091 do_writev+0x161/0x340 fs/read_write.c:1134 __do_sys_writev fs/read_write.c:1207 [inline] __se_sys_writev fs/read_write.c:1204 [inline] __x64_sys_writev+0x75/0xb0 fs/read_write.c:1204 do_syscall_64+0x32/0x80 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45b419 Code: 2d b6 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 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f9479d8bc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000014 RAX: ffffffffffffffda RBX: 00007f9479d8c6d4 RCX: 000000000045b419 RDX: 1000000000000252 RSI: 00000000200023c0 RDI: 0000000000000005 RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006 R13: 0000000000000cda R14: 00000000004c9d20 R15: 0000000000000002