====================================================== WARNING: possible circular locking dependency detected 5.5.0-rc2-next-20191220-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.3/11134 is trying to acquire lock: ffffffff899a48a0 (console_owner){-.-.}, at: console_trylock_spinning kernel/printk/printk.c:1724 [inline] ffffffff899a48a0 (console_owner){-.-.}, at: vprintk_emit+0x3fd/0x700 kernel/printk/printk.c:1995 but task is already holding lock: ffff8880a8057140 (&(&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: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+0x46/0x70 drivers/tty/serial/serial_core.c:104 serial8250_tx_chars+0x495/0xaf0 drivers/tty/serial/8250/8250_port.c:1757 serial8250_handle_irq.part.0+0x2f4/0x3a0 drivers/tty/serial/8250/8250_port.c:1830 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1816 [inline] serial8250_default_handle_irq+0xc0/0x150 drivers/tty/serial/8250/8250_port.c:1846 serial8250_interrupt+0xf1/0x1a0 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x15d/0x970 kernel/irq/handle.c:149 handle_irq_event_percpu+0x74/0x160 kernel/irq/handle.c:189 handle_irq_event+0xa7/0x134 kernel/irq/handle.c:206 handle_edge_irq+0x25e/0x8d0 kernel/irq/chip.c:830 generic_handle_irq_desc include/linux/irqdesc.h:156 [inline] do_IRQ+0xde/0x280 arch/x86/kernel/irq.c:250 ret_from_intr+0x0/0x36 arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline] _raw_spin_unlock_irqrestore+0x90/0xe0 kernel/locking/spinlock.c:191 spin_unlock_irqrestore include/linux/spinlock.h:393 [inline] uart_write+0x3a9/0x6c0 drivers/tty/serial/serial_core.c:613 process_output_block drivers/tty/n_tty.c:595 [inline] n_tty_write+0x40e/0x1080 drivers/tty/n_tty.c:2333 do_tty_write drivers/tty/tty_io.c:962 [inline] tty_write+0x496/0x7f0 drivers/tty/tty_io.c:1046 redirected_tty_write+0xb2/0xc0 drivers/tty/tty_io.c:1067 __vfs_write+0x8a/0x110 fs/read_write.c:494 vfs_write+0x268/0x5d0 fs/read_write.c:558 ksys_write+0x14f/0x290 fs/read_write.c:611 __do_sys_write fs/read_write.c:623 [inline] __se_sys_write fs/read_write.c:620 [inline] __x64_sys_write+0x73/0xb0 fs/read_write.c:620 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #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:159 serial8250_console_write+0x253/0x9a0 drivers/tty/serial/8250/8250_port.c:3139 univ8250_console_write+0x5f/0x70 drivers/tty/serial/8250/8250_core.c:587 call_console_drivers kernel/printk/printk.c:1791 [inline] console_unlock+0xb7a/0xf00 kernel/printk/printk.c:2473 vprintk_emit+0x2a0/0x700 kernel/printk/printk.c:1996 vprintk_default+0x28/0x30 kernel/printk/printk.c:2023 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:386 printk+0xba/0xed kernel/printk/printk.c:2056 register_console+0x745/0xb50 kernel/printk/printk.c:2798 univ8250_console_init+0x3e/0x4b drivers/tty/serial/8250/8250_core.c:682 console_init+0x461/0x67b kernel/printk/printk.c:2884 start_kernel+0x653/0x943 init/main.c:713 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:242 -> #0 (console_owner){-.-.}: check_prev_add kernel/locking/lockdep.c:2476 [inline] check_prevs_add kernel/locking/lockdep.c:2581 [inline] validate_chain kernel/locking/lockdep.c:2971 [inline] __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485 console_trylock_spinning kernel/printk/printk.c:1745 [inline] vprintk_emit+0x43a/0x700 kernel/printk/printk.c:1995 vprintk_default+0x28/0x30 kernel/printk/printk.c:2023 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:386 printk+0xba/0xed kernel/printk/printk.c:2056 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x6f1/0x860 lib/fault-inject.c:144 __should_failslab+0x121/0x190 mm/failslab.c:33 should_failslab+0x9/0x14 mm/slab_common.c:1788 slab_pre_alloc_hook mm/slab.h:567 [inline] slab_alloc mm/slab.c:3306 [inline] __do_kmalloc mm/slab.c:3654 [inline] __kmalloc+0x71/0x770 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+0x1fb/0x5c0 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_put_char+0x130/0x160 drivers/tty/tty_io.c:3034 __process_echoes+0x5c8/0xa40 drivers/tty/n_tty.c:728 flush_echoes drivers/tty/n_tty.c:829 [inline] __receive_buf drivers/tty/n_tty.c:1648 [inline] n_tty_receive_buf_common+0xc77/0x2b70 drivers/tty/n_tty.c:1742 n_tty_receive_buf+0x31/0x40 drivers/tty/n_tty.c:1771 tiocsti drivers/tty/tty_io.c:2200 [inline] tty_ioctl+0x949/0x14f0 drivers/tty/tty_io.c:2576 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x123/0x180 fs/ioctl.c:747 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 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-executor.3/11134: #0: ffff8880a6ca0090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffff8880a6ca02a0 (&o_tty->termios_rwsem/1){++++}, at: n_tty_receive_buf_common+0x8a/0x2b70 drivers/tty/n_tty.c:1705 #2: ffffc90017813360 (&ldata->output_lock){+.+.}, at: flush_echoes drivers/tty/n_tty.c:827 [inline] #2: ffffc90017813360 (&ldata->output_lock){+.+.}, at: __receive_buf drivers/tty/n_tty.c:1648 [inline] #2: ffffc90017813360 (&ldata->output_lock){+.+.}, at: n_tty_receive_buf_common+0xc3a/0x2b70 drivers/tty/n_tty.c:1742 #3: ffff8880a8057140 (&(&port->lock)->rlock){-.-.}, at: pty_write+0xff/0x200 drivers/tty/pty.c:120 stack backtrace: CPU: 1 PID: 11134 Comm: syz-executor.3 Not tainted 5.5.0-rc2-next-20191220-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+0x197/0x210 lib/dump_stack.c:118 print_circular_bug.isra.0.cold+0x163/0x172 kernel/locking/lockdep.c:1685 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1809 check_prev_add kernel/locking/lockdep.c:2476 [inline] check_prevs_add kernel/locking/lockdep.c:2581 [inline] validate_chain kernel/locking/lockdep.c:2971 [inline] __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485 console_trylock_spinning kernel/printk/printk.c:1745 [inline] vprintk_emit+0x43a/0x700 kernel/printk/printk.c:1995 vprintk_default+0x28/0x30 kernel/printk/printk.c:2023 vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:386 printk+0xba/0xed kernel/printk/printk.c:2056 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x6f1/0x860 lib/fault-inject.c:144 __should_failslab+0x121/0x190 mm/failslab.c:33 should_failslab+0x9/0x14 mm/slab_common.c:1788 slab_pre_alloc_hook mm/slab.h:567 [inline] slab_alloc mm/slab.c:3306 [inline] __do_kmalloc mm/slab.c:3654 [inline] __kmalloc+0x71/0x770 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+0x1fb/0x5c0 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_put_char+0x130/0x160 drivers/tty/tty_io.c:3034 __process_echoes+0x5c8/0xa40 drivers/tty/n_tty.c:728 flush_echoes drivers/tty/n_tty.c:829 [inline] __receive_buf drivers/tty/n_tty.c:1648 [inline] n_tty_receive_buf_common+0xc77/0x2b70 drivers/tty/n_tty.c:1742 n_tty_receive_buf+0x31/0x40 drivers/tty/n_tty.c:1771 tiocsti drivers/tty/tty_io.c:2200 [inline] tty_ioctl+0x949/0x14f0 drivers/tty/tty_io.c:2576 vfs_ioctl fs/ioctl.c:47 [inline] ksys_ioctl+0x123/0x180 fs/ioctl.c:747 __do_sys_ioctl fs/ioctl.c:756 [inline] __se_sys_ioctl fs/ioctl.c:754 [inline] __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:754 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45a919 Code: ad 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f1bba6c7c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f1bba6c7c90 RCX: 000000000045a919 RDX: 0000000020000040 RSI: 0000000000005412 RDI: 0000000000000004 RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f1bba6c86d4 R13: 00000000004c5a54 R14: 00000000004dbd50 R15: 0000000000000005