bisecting fixing commit since 11a48a5a18c63fd7621bb050228cebf13566e4d8 building syzkaller on 2b41159686513694e75f8c376b4a32c66c8b709f testing commit 11a48a5a18c63fd7621bb050228cebf13566e4d8 with gcc (GCC) 8.1.0 kernel signature: d26095da48b3cc6c55a5752eeb2a0128316f1e25f9e622b4157fb6ce05182d6e run #0: crashed: possible deadlock in console_unlock run #1: crashed: possible deadlock in console_unlock run #2: crashed: possible deadlock in console_unlock run #3: crashed: possible deadlock in console_unlock run #4: crashed: possible deadlock in tty_port_close_start run #5: crashed: possible deadlock in console_unlock run #6: crashed: possible deadlock in tty_port_close_start run #7: crashed: possible deadlock in console_unlock run #8: crashed: possible deadlock in console_unlock run #9: crashed: possible deadlock in tty_port_close_start testing current HEAD d4fb4bfb37172dbe107aa6f093508fe80c73a46d testing commit d4fb4bfb37172dbe107aa6f093508fe80c73a46d with gcc (GCC) 8.1.0 kernel signature: 52674a11b731ff39ad8d8a56e97bb03bade417b967602c64e3d35f599f90936b run #0: crashed: possible deadlock in console_unlock run #1: crashed: possible deadlock in tty_port_close_start run #2: crashed: possible deadlock in console_unlock run #3: crashed: possible deadlock in console_unlock run #4: crashed: possible deadlock in tty_port_close_start run #5: crashed: possible deadlock in console_unlock run #6: crashed: possible deadlock in console_unlock run #7: crashed: possible deadlock in console_unlock run #8: crashed: possible deadlock in console_unlock run #9: crashed: possible deadlock in console_unlock revisions tested: 2, total time: 19m5.247966392s (build: 11m41.589210433s, test: 6m31.659829113s) the crash still happens on HEAD commit msg: Merge tag '5.7-rc2-smb3-fixes' of git://git.samba.org/sfrench/cifs-2.6 crash: possible deadlock in console_unlock ====================================================== WARNING: possible circular locking dependency detected 5.7.0-rc2-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.1/8430 is trying to acquire lock: ffffffff891abfc0 (console_owner){-.-.}-{0:0}, at: log_next kernel/printk/printk.c:524 [inline] ffffffff891abfc0 (console_owner){-.-.}-{0:0}, at: console_unlock+0x36b/0xbd0 kernel/printk/printk.c:2485 but task is already holding lock: ffffffff8b8eda58 (&port->lock#2){-.-.}-{2:2}, at: tty_port_close_start.part.4+0x26/0x450 drivers/tty/tty_port.c:567 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+0x99/0xd0 kernel/locking/spinlock.c:159 tty_port_tty_get+0x1d/0xb0 drivers/tty/tty_port.c:288 tty_port_default_wakeup+0xa/0x30 drivers/tty/tty_port.c:47 tty_port_tty_wakeup+0x53/0x70 drivers/tty/tty_port.c:388 uart_write_wakeup+0x37/0x50 drivers/tty/serial/serial_core.c:107 serial8250_tx_chars+0x3dc/0x960 drivers/tty/serial/8250/8250_port.c:1828 serial8250_handle_irq.part.25+0x22c/0x2e0 drivers/tty/serial/8250/8250_port.c:1915 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1888 [inline] serial8250_default_handle_irq+0x7c/0xe0 drivers/tty/serial/8250/8250_port.c:1931 serial8250_interrupt+0xcc/0x150 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x1b8/0x790 kernel/irq/handle.c:156 handle_irq_event_percpu+0x6c/0x140 kernel/irq/handle.c:196 handle_irq_event+0xa2/0x130 kernel/irq/handle.c:213 handle_edge_irq+0x206/0x780 kernel/irq/chip.c:830 generic_handle_irq_desc include/linux/irqdesc.h:156 [inline] do_IRQ+0xde/0x270 arch/x86/kernel/irq.c:250 ret_from_intr+0x0/0x2b arch_local_irq_restore arch/x86/include/asm/paravirt.h:759 [inline] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline] _raw_spin_unlock_irqrestore+0xaa/0xd0 kernel/locking/spinlock.c:191 spin_unlock_irqrestore include/linux/spinlock.h:408 [inline] uart_write+0x329/0x620 drivers/tty/serial/serial_core.c:616 do_output_char+0x4e8/0x700 drivers/tty/n_tty.c:447 process_output drivers/tty/n_tty.c:514 [inline] n_tty_write+0x519/0xfa0 drivers/tty/n_tty.c:2345 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x377/0x7e0 drivers/tty/tty_io.c:1046 redirected_tty_write+0xa5/0xc0 drivers/tty/tty_io.c:1067 do_loop_readv_writev fs/read_write.c:718 [inline] do_iter_write+0x378/0x510 fs/read_write.c:1001 vfs_writev+0x16d/0x2d0 fs/read_write.c:1072 do_writev+0x118/0x2e0 fs/read_write.c:1115 __do_sys_writev fs/read_write.c:1188 [inline] __se_sys_writev fs/read_write.c:1185 [inline] __x64_sys_writev+0x70/0xb0 fs/read_write.c:1185 do_syscall_64+0xca/0x630 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 -> #1 (&port->lock){-.-.}-{2:2}: __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+0x1df/0x970 drivers/tty/serial/8250/8250_port.c:3240 univ8250_console_write+0x4e/0x70 drivers/tty/serial/8250/8250_core.c:586 call_console_drivers kernel/printk/printk.c:1816 [inline] console_unlock+0x86a/0xbd0 kernel/printk/printk.c:2498 vprintk_emit+0x19a/0x560 kernel/printk/printk.c:2021 vprintk_default+0x1a/0x20 kernel/printk/printk.c:2048 vprintk_func+0x49/0x12c kernel/printk/printk_safe.c:385 printk+0x9a/0xc0 kernel/printk/printk.c:2081 register_console+0x656/0x980 kernel/printk/printk.c:2821 univ8250_console_init+0x1e/0x28 drivers/tty/serial/8250/8250_core.c:690 console_init+0x2ef/0x445 kernel/printk/printk.c:2921 start_kernel+0x4d9/0x709 init/main.c:931 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){-.-.}-{0:0}: check_prev_add kernel/locking/lockdep.c:2515 [inline] check_prevs_add kernel/locking/lockdep.c:2620 [inline] validate_chain kernel/locking/lockdep.c:3237 [inline] __lock_acquire+0x26d7/0x3bf0 kernel/locking/lockdep.c:4355 lock_acquire+0x209/0x9e0 kernel/locking/lockdep.c:4934 console_lock_spinning_enable kernel/printk/printk.c:1682 [inline] console_unlock+0x3cd/0xbd0 kernel/printk/printk.c:2495 vprintk_emit+0x19a/0x560 kernel/printk/printk.c:2021 vprintk_default+0x1a/0x20 kernel/printk/printk.c:2048 vprintk_func+0x49/0x12c kernel/printk/printk_safe.c:385 printk+0x9a/0xc0 kernel/printk/printk.c:2081 tty_port_close_start.part.4+0x403/0x450 drivers/tty/tty_port.c:569 tty_port_close_start drivers/tty/tty_port.c:641 [inline] tty_port_close+0x29/0xb0 drivers/tty/tty_port.c:634 tpk_close+0x77/0x8d drivers/char/ttyprintk.c:110 tty_release+0x32c/0xc60 drivers/tty/tty_io.c:1679 __fput+0x2a7/0x790 fs/file_table.c:280 ____fput+0x9/0x10 fs/file_table.c:313 task_work_run+0xcc/0x160 kernel/task_work.c:123 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x24e/0x2e0 arch/x86/entry/common.c:165 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline] syscall_return_slowpath arch/x86/entry/common.c:279 [inline] do_syscall_64+0x531/0x630 arch/x86/entry/common.c:305 entry_SYSCALL_64_after_hwframe+0x49/0xb3 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 *** 3 locks held by syz-executor.1/8430: #0: ffff8880986b71c0 (&tty->legacy_mutex){+.+.}-{3:3}, at: tty_lock+0x68/0xb0 drivers/tty/tty_mutex.c:19 #1: ffffffff8b8eda58 (&port->lock#2){-.-.}-{2:2}, at: tty_port_close_start.part.4+0x26/0x450 drivers/tty/tty_port.c:567 #2: ffffffff891ac240 (console_lock){+.+.}-{0:0}, at: console_trylock_spinning kernel/printk/printk.c:1744 [inline] #2: ffffffff891ac240 (console_lock){+.+.}-{0:0}, at: vprintk_emit+0x18d/0x560 kernel/printk/printk.c:2020 stack backtrace: CPU: 1 PID: 8430 Comm: syz-executor.1 Not tainted 5.7.0-rc2-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.41.cold.60+0x15a/0x169 kernel/locking/lockdep.c:1722 check_noncircular+0x349/0x400 kernel/locking/lockdep.c:1846 check_prev_add kernel/locking/lockdep.c:2515 [inline] check_prevs_add kernel/locking/lockdep.c:2620 [inline] validate_chain kernel/locking/lockdep.c:3237 [inline] __lock_acquire+0x26d7/0x3bf0 kernel/locking/lockdep.c:4355 lock_acquire+0x209/0x9e0 kernel/locking/lockdep.c:4934 console_lock_spinning_enable kernel/printk/printk.c:1682 [inline] console_unlock+0x3cd/0xbd0 kernel/printk/printk.c:2495 vprintk_emit+0x19a/0x560 kernel/printk/printk.c:2021 vprintk_default+0x1a/0x20 kernel/printk/printk.c:2048 vprintk_func+0x49/0x12c kernel/printk/printk_safe.c:385 printk+0x9a/0xc0 kernel/printk/printk.c:2081 tty_port_close_start.part.4+0x403/0x450 drivers/tty/tty_port.c:569 tty_port_close_start drivers/tty/tty_port.c:641 [inline] tty_port_close+0x29/0xb0 drivers/tty/tty_port.c:634 tpk_close+0x77/0x8d drivers/char/ttyprintk.c:110 tty_release+0x32c/0xc60 drivers/tty/tty_io.c:1679 __fput+0x2a7/0x790 fs/file_table.c:280 ____fput+0x9/0x10 fs/file_table.c:313 task_work_run+0xcc/0x160 kernel/task_work.c:123 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x24e/0x2e0 arch/x86/entry/common.c:165 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline] syscall_return_slowpath arch/x86/entry/common.c:279 [inline] do_syscall_64+0x531/0x630 arch/x86/entry/common.c:305 entry_SYSCALL_64_after_hwframe+0x49/0xb3 RIP: 0033:0x416261 Code: 75 14 b8 03 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff 48 89 04 24 b8 03 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 53 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01 RSP: 002b:00007ffe04f2be10 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000416261 RDX: 00000000000f4240 RSI: 0000000000000081 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000770120 R09: ffffffffffffffff R10: 00007ffe04f2bee0 R11: 0000000000000293 R12: 000000000076bf20 R13: 0000000000000003 R14: 0000000000770128 R15: 000000000076bf2c