bisecting fixing commit since ccaaaf6fe5a5e1fffca5cca0f3fc4ec84d7ae752 building syzkaller on c30117b2ace7866719409f4c11bf5433062b8169 testing commit ccaaaf6fe5a5e1fffca5cca0f3fc4ec84d7ae752 with gcc (GCC) 8.1.0 kernel signature: d7e54e3b19be8bcffbbb8f03319905c03d019aa8a4e57e576a5010c527c79ad6 run #0: crashed: possible deadlock in console_unlock run #1: crashed: possible deadlock in pty_write run #2: crashed: possible deadlock in pty_write run #3: crashed: possible deadlock in pty_write run #4: crashed: possible deadlock in pty_write run #5: crashed: possible deadlock in console_unlock run #6: crashed: possible deadlock in pty_write run #7: crashed: possible deadlock in pty_write run #8: crashed: possible deadlock in pty_write run #9: boot failed: can't ssh into the instance testing current HEAD f8394f232b1eab649ce2df5c5f15b0e528c92091 testing commit f8394f232b1eab649ce2df5c5f15b0e528c92091 with gcc (GCC) 8.1.0 kernel signature: 1059110cf9e371897ec07f2079be8bb6cfb3cf98049a8c856d0eebd3c9866f9a run #0: crashed: possible deadlock in pty_write run #1: crashed: possible deadlock in pty_write run #2: crashed: possible deadlock in console_unlock run #3: crashed: possible deadlock in console_unlock run #4: crashed: possible deadlock in console_unlock run #5: crashed: possible deadlock in pty_write run #6: crashed: possible deadlock in pty_write run #7: crashed: possible deadlock in console_unlock run #8: crashed: possible deadlock in pty_write run #9: crashed: possible deadlock in console_unlock revisions tested: 2, total time: 25m16.445832501s (build: 11m2.468023232s, test: 13m4.555165393s) the crash still happens on HEAD commit msg: Linux 5.10-rc3 crash: possible deadlock in console_unlock ====================================================== WARNING: possible circular locking dependency detected 5.10.0-rc3-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.0/8261 is trying to acquire lock: ffffffff842e1980 (console_owner){..-.}-{0:0}, at: console_unlock+0x18b/0x640 kernel/printk/printk.c:2474 but task is already holding lock: ffff88812093d158 (&port->lock){-.-.}-{2:2}, at: pty_write+0x44/0x90 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}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x5d/0x80 kernel/locking/spinlock.c:159 tty_port_tty_get+0x1d/0x90 drivers/tty/tty_port.c:288 tty_port_default_wakeup+0xa/0x30 drivers/tty/tty_port.c:47 tty_port_tty_wakeup+0xe/0x10 drivers/tty/tty_port.c:388 uart_write_wakeup+0x15/0x20 drivers/tty/serial/serial_core.c:106 serial8250_tx_chars+0x111/0x1d0 drivers/tty/serial/8250/8250_port.c:1832 serial8250_handle_irq.part.29+0xd1/0xe0 drivers/tty/serial/8250/8250_port.c:1919 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1892 [inline] serial8250_default_handle_irq+0x34/0x50 drivers/tty/serial/8250/8250_port.c:1935 serial8250_interrupt+0x57/0xa0 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x85/0x360 kernel/irq/handle.c:156 handle_irq_event_percpu+0x2d/0x80 kernel/irq/handle.c:196 handle_irq_event+0x34/0x60 kernel/irq/handle.c:213 handle_edge_irq+0x94/0x1c0 kernel/irq/chip.c:819 asm_call_irq_on_stack+0xf/0x20 __run_irq_on_irqstack arch/x86/include/asm/irq_stack.h:48 [inline] run_irq_on_irqstack_cond arch/x86/include/asm/irq_stack.h:101 [inline] handle_irq arch/x86/kernel/irq.c:230 [inline] __common_interrupt arch/x86/kernel/irq.c:249 [inline] common_interrupt+0x182/0x250 arch/x86/kernel/irq.c:239 asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:622 native_safe_halt+0x12/0x20 arch/x86/include/asm/irqflags.h:60 arch_safe_halt arch/x86/include/asm/paravirt.h:150 [inline] acpi_safe_halt drivers/acpi/processor_idle.c:111 [inline] acpi_idle_do_entry+0x57/0xa0 drivers/acpi/processor_idle.c:517 acpi_idle_enter+0xa5/0x100 drivers/acpi/processor_idle.c:648 cpuidle_enter_state+0x9e/0x520 drivers/cpuidle/cpuidle.c:237 cpuidle_enter+0x29/0x40 drivers/cpuidle/cpuidle.c:351 call_cpuidle kernel/sched/idle.c:132 [inline] cpuidle_idle_call kernel/sched/idle.c:213 [inline] do_idle+0x2e9/0x360 kernel/sched/idle.c:273 cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:369 rest_init+0x174/0x237 init/main.c:711 arch_call_rest_init+0x9/0xc start_kernel+0x4ed/0x50d init/main.c:1051 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:526 x86_64_start_kernel+0x71/0x74 arch/x86/kernel/head64.c:507 secondary_startup_64_no_verify+0xb0/0xbb -> #1 (&port_lock_key){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x5d/0x80 kernel/locking/spinlock.c:159 serial8250_console_write+0xbe/0x330 drivers/tty/serial/8250/8250_port.c:3292 univ8250_console_write+0x1c/0x20 drivers/tty/serial/8250/8250_core.c:586 call_console_drivers kernel/printk/printk.c:1885 [inline] console_unlock+0x53d/0x640 kernel/printk/printk.c:2499 vprintk_emit+0x159/0x380 kernel/printk/printk.c:2028 vprintk_default+0x18/0x20 kernel/printk/printk.c:2045 vprintk_func+0x59/0xe0 kernel/printk/printk_safe.c:393 printk+0x53/0x6a kernel/printk/printk.c:2076 register_console+0x175/0x2b0 kernel/printk/printk.c:2850 univ8250_console_init+0x1e/0x28 drivers/tty/serial/8250/8250_core.c:690 console_init+0x18e/0x24a kernel/printk/printk.c:2950 start_kernel+0x420/0x50d init/main.c:978 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:526 x86_64_start_kernel+0x71/0x74 arch/x86/kernel/head64.c:507 secondary_startup_64_no_verify+0xb0/0xbb -> #0 (console_owner){..-.}-{0:0}: check_prev_add kernel/locking/lockdep.c:2864 [inline] check_prevs_add kernel/locking/lockdep.c:2989 [inline] validate_chain kernel/locking/lockdep.c:3607 [inline] __lock_acquire+0x1084/0x17d0 kernel/locking/lockdep.c:4831 lock_acquire+0xf9/0x410 kernel/locking/lockdep.c:5436 console_lock_spinning_enable kernel/printk/printk.c:1737 [inline] console_unlock+0x20a/0x640 kernel/printk/printk.c:2496 vprintk_emit+0x159/0x380 kernel/printk/printk.c:2028 vprintk_default+0x18/0x20 kernel/printk/printk.c:2045 vprintk_func+0x59/0xe0 kernel/printk/printk_safe.c:393 printk+0x53/0x6a kernel/printk/printk.c:2076 fail_dump lib/fault-inject.c:45 [inline] should_fail.cold.6+0x22/0x37 lib/fault-inject.c:146 __should_failslab+0x41/0x50 mm/failslab.c:33 should_failslab+0x9/0x20 mm/slab_common.c:1194 slab_pre_alloc_hook mm/slab.h:508 [inline] slab_alloc mm/slab.c:3300 [inline] __do_kmalloc mm/slab.c:3655 [inline] __kmalloc+0x82/0x7d0 mm/slab.c:3666 kmalloc include/linux/slab.h:557 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline] __tty_buffer_request_room+0x84/0x130 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x54/0xd0 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0x5b/0x90 drivers/tty/pty.c:122 n_tty_write+0x3b7/0x4d0 drivers/tty/n_tty.c:2356 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x15e/0x320 drivers/tty/tty_io.c:1046 do_loop_readv_writev fs/read_write.c:764 [inline] do_iter_write+0x145/0x1b0 fs/read_write.c:868 vfs_writev+0x9e/0x100 fs/read_write.c:939 do_writev+0x6e/0x110 fs/read_write.c:982 __do_sys_writev fs/read_write.c:1055 [inline] __se_sys_writev fs/read_write.c:1052 [inline] __x64_sys_writev+0x17/0x20 fs/read_write.c:1052 do_syscall_64+0x31/0x80 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_key --> &port->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&port->lock); lock(&port_lock_key); lock(&port->lock); lock(console_owner); *** DEADLOCK *** 6 locks held by syz-executor.0/8261: #0: ffff888120215898 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:340 #1: ffff888120215930 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock+0x19/0x50 drivers/tty/tty_io.c:888 #2: ffff888120215ae8 (&tty->termios_rwsem){++++}-{3:3}, at: n_tty_write+0x9a/0x4d0 drivers/tty/n_tty.c:2316 #3: ffffc90002e6b378 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_write+0x3a7/0x4d0 drivers/tty/n_tty.c:2355 #4: ffff88812093d158 (&port->lock){-.-.}-{2:2}, at: pty_write+0x44/0x90 drivers/tty/pty.c:120 #5: ffffffff843c1b00 (console_lock){+.+.}-{0:0}, at: console_trylock_spinning kernel/printk/printk.c:1799 [inline] #5: ffffffff843c1b00 (console_lock){+.+.}-{0:0}, at: vprintk_emit+0x150/0x380 kernel/printk/printk.c:2027 stack backtrace: CPU: 1 PID: 8261 Comm: syz-executor.0 Not tainted 5.10.0-rc3-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+0xa9/0xd1 lib/dump_stack.c:118 print_circular_bug.isra.45.cold.69+0x13d/0x142 kernel/locking/lockdep.c:1994 check_noncircular+0xfe/0x110 kernel/locking/lockdep.c:2115 check_prev_add kernel/locking/lockdep.c:2864 [inline] check_prevs_add kernel/locking/lockdep.c:2989 [inline] validate_chain kernel/locking/lockdep.c:3607 [inline] __lock_acquire+0x1084/0x17d0 kernel/locking/lockdep.c:4831 lock_acquire+0xf9/0x410 kernel/locking/lockdep.c:5436 console_lock_spinning_enable kernel/printk/printk.c:1737 [inline] console_unlock+0x20a/0x640 kernel/printk/printk.c:2496 vprintk_emit+0x159/0x380 kernel/printk/printk.c:2028 vprintk_default+0x18/0x20 kernel/printk/printk.c:2045 vprintk_func+0x59/0xe0 kernel/printk/printk_safe.c:393 printk+0x53/0x6a kernel/printk/printk.c:2076 fail_dump lib/fault-inject.c:45 [inline] should_fail.cold.6+0x22/0x37 lib/fault-inject.c:146 __should_failslab+0x41/0x50 mm/failslab.c:33 should_failslab+0x9/0x20 mm/slab_common.c:1194 slab_pre_alloc_hook mm/slab.h:508 [inline] slab_alloc mm/slab.c:3300 [inline] __do_kmalloc mm/slab.c:3655 [inline] __kmalloc+0x82/0x7d0 mm/slab.c:3666 kmalloc include/linux/slab.h:557 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline] __tty_buffer_request_room+0x84/0x130 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x54/0xd0 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0x5b/0x90 drivers/tty/pty.c:122 n_tty_write+0x3b7/0x4d0 drivers/tty/n_tty.c:2356 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x15e/0x320 drivers/tty/tty_io.c:1046 do_loop_readv_writev fs/read_write.c:764 [inline] do_iter_write+0x145/0x1b0 fs/read_write.c:868 vfs_writev+0x9e/0x100 fs/read_write.c:939 do_writev+0x6e/0x110 fs/read_write.c:982 __do_sys_writev fs/read_write.c:1055 [inline] __se_sys_writev fs/read_write.c:1052 [inline] __x64_sys_writev+0x17/0x20 fs/read_write.c:1052 do_syscall_64+0x31/0x80 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:00007f40e23afc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000014 RAX: ffffffffffffffda RBX: 00007f40e23b06d4 RCX: 000000000045b419 RDX: 1000000000000252 RSI: 00000000200023c0 RDI: 0000000000000005 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000006 R13: 0000000000000cda R14: 00000000004c9d20 R15: 0000000000000002