====================================================== WARNING: possible circular locking dependency detected 5.8.0-rc6-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/16558 is trying to acquire lock: ffffffff894e7950 (console_owner){-.-.}-{0:0}, at: console_trylock_spinning+0x11a/0x380 kernel/printk/printk.c:1756 but task is already holding lock: ffff8880919e7158 (&port->lock#2){-.-.}-{2:2}, at: pty_write+0xb6/0x180 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}: lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x9e/0xc0 kernel/locking/spinlock.c:159 tty_port_tty_get+0x21/0xe0 drivers/tty/tty_port.c:288 tty_port_default_wakeup+0x11/0x40 drivers/tty/tty_port.c:47 serial8250_tx_chars+0x5ea/0x800 drivers/tty/serial/8250/8250_port.c:1831 serial8250_handle_irq+0x2fd/0x3e0 drivers/tty/serial/8250/8250_port.c:1918 serial8250_default_handle_irq+0xac/0x190 drivers/tty/serial/8250/8250_port.c:1934 serial8250_interrupt+0x93/0x180 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x1b7/0x610 kernel/irq/handle.c:156 handle_irq_event_percpu kernel/irq/handle.c:196 [inline] handle_irq_event+0xbd/0x280 kernel/irq/handle.c:213 handle_edge_irq+0x245/0xbf0 kernel/irq/chip.c:830 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711 __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+0x155/0x260 arch/x86/kernel/irq.c:239 asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:576 arch_local_irq_restore arch/x86/include/asm/paravirt.h:770 [inline] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline] _raw_spin_unlock_irqrestore+0xa5/0xd0 kernel/locking/spinlock.c:191 spin_unlock_irqrestore include/linux/spinlock.h:408 [inline] uart_write+0x767/0x8f0 drivers/tty/serial/serial_core.c:614 do_output_char+0x63b/0x940 drivers/tty/n_tty.c:447 process_output drivers/tty/n_tty.c:514 [inline] n_tty_write+0xd5c/0x1170 drivers/tty/n_tty.c:2345 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x593/0x940 drivers/tty/tty_io.c:1046 do_loop_readv_writev fs/read_write.c:737 [inline] do_iter_write+0x402/0x540 fs/read_write.c:1020 vfs_writev fs/read_write.c:1091 [inline] do_writev+0x23f/0x4a0 fs/read_write.c:1134 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #1 (&port->lock){-.-.}-{2:2}: lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x9e/0xc0 kernel/locking/spinlock.c:159 serial8250_console_write+0x13e/0xd60 drivers/tty/serial/8250/8250_port.c:3245 call_console_drivers kernel/printk/printk.c:1814 [inline] console_unlock+0x90c/0xec0 kernel/printk/printk.c:2493 vprintk_emit+0x1f8/0x3c0 kernel/printk/printk.c:2021 printk+0x62/0x83 kernel/printk/printk.c:2070 register_console+0x7ca/0xad0 kernel/printk/printk.c:2846 univ8250_console_init+0x41/0x43 drivers/tty/serial/8250/8250_core.c:690 console_init+0x52/0x97 kernel/printk/printk.c:2946 start_kernel+0x426/0x777 init/main.c:970 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+0x1b0c/0x8920 kernel/locking/lockdep.c:3218 __lock_acquire+0x116c/0x2c30 kernel/locking/lockdep.c:4380 lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959 console_trylock_spinning+0x13a/0x380 kernel/printk/printk.c:1773 vprintk_emit+0x1db/0x3c0 kernel/printk/printk.c:2020 printk+0x62/0x83 kernel/printk/printk.c:2070 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x36c/0x4e0 lib/fault-inject.c:146 should_failslab+0x5/0x20 mm/slab_common.c:1811 slab_pre_alloc_hook mm/slab.h:569 [inline] slab_alloc mm/slab.c:3306 [inline] __do_kmalloc mm/slab.c:3654 [inline] __kmalloc+0x74/0x330 mm/slab.c:3665 kmalloc include/linux/slab.h:560 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline] __tty_buffer_request_room+0x1f3/0x540 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x91/0x2c0 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0xda/0x180 drivers/tty/pty.c:122 tty_put_char+0xc7/0x110 drivers/tty/tty_io.c:3032 __process_echoes+0x1a9/0x930 drivers/tty/n_tty.c:746 process_echoes drivers/tty/n_tty.c:811 [inline] n_tty_set_termios+0xbce/0x1080 drivers/tty/n_tty.c:1870 tty_set_termios+0xcac/0x1510 drivers/tty/tty_ioctl.c:341 set_termios+0x4a1/0x580 drivers/tty/tty_ioctl.c:414 tty_mode_ioctl+0x7b2/0xa80 drivers/tty/tty_ioctl.c:770 tty_ioctl+0xf81/0x15c0 drivers/tty/tty_io.c:2665 vfs_ioctl fs/ioctl.c:48 [inline] ksys_ioctl fs/ioctl.c:753 [inline] __do_sys_ioctl fs/ioctl.c:762 [inline] __se_sys_ioctl+0xf9/0x160 fs/ioctl.c:760 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 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 *** 5 locks held by syz-executor.4/16558: #0: ffff8880940f4098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:267 #1: ffff888097e182e8 (&o_tty->termios_rwsem/1){++++}-{3:3}, at: tty_set_termios+0xc5/0x1510 drivers/tty/tty_ioctl.c:328 #2: ffff888097e18098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref+0x18/0x80 drivers/tty/tty_ldisc.c:288 #3: ffffc90017b23378 (&ldata->output_lock){+.+.}-{3:3}, at: process_echoes drivers/tty/n_tty.c:809 [inline] #3: ffffc90017b23378 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_set_termios+0xb82/0x1080 drivers/tty/n_tty.c:1870 #4: ffff8880919e7158 (&port->lock#2){-.-.}-{2:2}, at: pty_write+0xb6/0x180 drivers/tty/pty.c:120 stack backtrace: CPU: 1 PID: 16558 Comm: syz-executor.4 Not tainted 5.8.0-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+0x1f0/0x31e lib/dump_stack.c:118 print_circular_bug+0xc72/0xea0 kernel/locking/lockdep.c:1703 check_noncircular+0x1fb/0x3a0 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+0x1b0c/0x8920 kernel/locking/lockdep.c:3218 __lock_acquire+0x116c/0x2c30 kernel/locking/lockdep.c:4380 lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959 console_trylock_spinning+0x13a/0x380 kernel/printk/printk.c:1773 vprintk_emit+0x1db/0x3c0 kernel/printk/printk.c:2020 printk+0x62/0x83 kernel/printk/printk.c:2070 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x36c/0x4e0 lib/fault-inject.c:146 should_failslab+0x5/0x20 mm/slab_common.c:1811 slab_pre_alloc_hook mm/slab.h:569 [inline] slab_alloc mm/slab.c:3306 [inline] __do_kmalloc mm/slab.c:3654 [inline] __kmalloc+0x74/0x330 mm/slab.c:3665 kmalloc include/linux/slab.h:560 [inline] tty_buffer_alloc drivers/tty/tty_buffer.c:175 [inline] __tty_buffer_request_room+0x1f3/0x540 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x91/0x2c0 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0xda/0x180 drivers/tty/pty.c:122 tty_put_char+0xc7/0x110 drivers/tty/tty_io.c:3032 __process_echoes+0x1a9/0x930 drivers/tty/n_tty.c:746 process_echoes drivers/tty/n_tty.c:811 [inline] n_tty_set_termios+0xbce/0x1080 drivers/tty/n_tty.c:1870 tty_set_termios+0xcac/0x1510 drivers/tty/tty_ioctl.c:341 set_termios+0x4a1/0x580 drivers/tty/tty_ioctl.c:414 tty_mode_ioctl+0x7b2/0xa80 drivers/tty/tty_ioctl.c:770 tty_ioctl+0xf81/0x15c0 drivers/tty/tty_io.c:2665 vfs_ioctl fs/ioctl.c:48 [inline] ksys_ioctl fs/ioctl.c:753 [inline] __do_sys_ioctl fs/ioctl.c:762 [inline] __se_sys_ioctl+0xf9/0x160 fs/ioctl.c:760 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45c369 Code: 8d 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 5b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ff430121c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000017280 RCX: 000000000045c369 RDX: 0000000020000080 RSI: 0000000000005408 RDI: 0000000000000003 RBP: 00007ff430121ca0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002 R13: 00007fff7745d79f R14: 00007ff4301229c0 R15: 000000000078bf0c