syzbot

RDX: 0000000000000002 RSI: 000000000000540a RDI: 0000000000000003
RBP: 00007ffcb2860640 R08: 0000000000000001 R09: 00007f6d27fc0031
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
======================================================
WARNING: possible circular locking dependency detected
4.14.305-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor406/7987 is trying to acquire lock:
 (console_owner){....}, at: [<ffffffff81440a17>] log_next kernel/printk/printk.c:495 [inline]
 (console_owner){....}, at: [<ffffffff81440a17>] console_unlock+0x307/0xf20 kernel/printk/printk.c:2396

but task is already holding lock:
 (&(&port->lock)->rlock){-.-.}, at: [<ffffffff83560b1b>] tty_insert_flip_string_and_push_buffer+0x2b/0x160 drivers/tty/tty_buffer.c:569

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+0x8c/0xc0 kernel/locking/spinlock.c:160
       tty_port_tty_get+0x1d/0x80 drivers/tty/tty_port.c:288
       tty_port_default_wakeup+0x11/0x40 drivers/tty/tty_port.c:46
       serial8250_tx_chars+0x3fe/0xc70 drivers/tty/serial/8250/8250_port.c:1828
       serial8250_handle_irq.part.0+0x2c7/0x390 drivers/tty/serial/8250/8250_port.c:1918
       serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1891 [inline]
       serial8250_default_handle_irq+0x8a/0x1f0 drivers/tty/serial/8250/8250_port.c:1934
       serial8250_interrupt+0xf3/0x210 drivers/tty/serial/8250/8250_core.c:129
       __handle_irq_event_percpu+0xee/0x7f0 kernel/irq/handle.c:147
       handle_irq_event_percpu kernel/irq/handle.c:187 [inline]
       handle_irq_event+0xed/0x240 kernel/irq/handle.c:204
       handle_edge_irq+0x224/0xc40 kernel/irq/chip.c:770
       generic_handle_irq_desc include/linux/irqdesc.h:159 [inline]
       handle_irq+0x35/0x50 arch/x86/kernel/irq_64.c:87
       do_IRQ+0x93/0x1d0 arch/x86/kernel/irq.c:230
       ret_from_intr+0x0/0x1e
       native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60
       arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
       default_idle+0x47/0x370 arch/x86/kernel/process.c:558
       cpuidle_idle_call kernel/sched/idle.c:156 [inline]
       do_idle+0x250/0x3c0 kernel/sched/idle.c:246
       cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:351
       start_kernel+0x743/0x763 init/main.c:712
       secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:240

-> #1 (&port_lock_key){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x8c/0xc0 kernel/locking/spinlock.c:160
       serial8250_console_write+0x8cb/0xb40 drivers/tty/serial/8250/8250_port.c:3281
       call_console_drivers kernel/printk/printk.c:1727 [inline]
       console_unlock+0x99d/0xf20 kernel/printk/printk.c:2409
       vprintk_emit+0x224/0x620 kernel/printk/printk.c:1925
       vprintk_func+0x58/0x160 kernel/printk/printk_safe.c:409
       printk+0x9e/0xbc kernel/printk/printk.c:1998
       register_console+0x6f4/0xad0 kernel/printk/printk.c:2728
       univ8250_console_init+0x2f/0x3a drivers/tty/serial/8250/8250_core.c:691
       console_init+0x46/0x53 kernel/printk/printk.c:2809
       start_kernel+0x521/0x763 init/main.c:638
       secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:240

-> #0 (console_owner){....}:
       lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
       console_lock_spinning_enable kernel/printk/printk.c:1590 [inline]
       console_unlock+0x36f/0xf20 kernel/printk/printk.c:2406
       vprintk_emit+0x224/0x620 kernel/printk/printk.c:1925
       vprintk_func+0x58/0x160 kernel/printk/printk_safe.c:409
       printk+0x9e/0xbc kernel/printk/printk.c:1998
       fail_dump lib/fault-inject.c:44 [inline]
       should_fail.cold+0xdf/0x149 lib/fault-inject.c:149
       should_failslab+0xd6/0x130 mm/failslab.c:32
       slab_pre_alloc_hook mm/slab.h:421 [inline]
       slab_alloc mm/slab.c:3376 [inline]
       __do_kmalloc mm/slab.c:3718 [inline]
       __kmalloc+0x6d/0x400 mm/slab.c:3729
       kmalloc include/linux/slab.h:493 [inline]
       tty_buffer_alloc+0xc0/0x270 drivers/tty/tty_buffer.c:169
       __tty_buffer_request_room+0x12c/0x290 drivers/tty/tty_buffer.c:268
       tty_insert_flip_string_fixed_flag+0x8b/0x210 drivers/tty/tty_buffer.c:313
       tty_insert_flip_string include/linux/tty_flip.h:36 [inline]
       tty_insert_flip_string_and_push_buffer+0x3e/0x160 drivers/tty/tty_buffer.c:570
       pty_write+0xc3/0xf0 drivers/tty/pty.c:118
       tty_send_xchar+0x245/0x360 drivers/tty/tty_io.c:1092
       n_tty_ioctl_helper+0x145/0x350 drivers/tty/tty_ioctl.c:926
       n_tty_ioctl+0x47/0x2e0 drivers/tty/n_tty.c:2466
       tty_ioctl+0x5af/0x1430 drivers/tty/tty_io.c:2670
       vfs_ioctl fs/ioctl.c:46 [inline]
       file_ioctl fs/ioctl.c:500 [inline]
       do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684
       SYSC_ioctl fs/ioctl.c:701 [inline]
       SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
       do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
       entry_SYSCALL_64_after_hwframe+0x5e/0xd3

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 ***

5 locks held by syz-executor406/7987:
 #0:  (&tty->ldisc_sem){++++}, at: [<ffffffff8355cf92>] tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:284
 #1:  (&tty->atomic_write_lock){+.+.}, at: [<ffffffff8354be65>] tty_write_lock drivers/tty/tty_io.c:885 [inline]
 #1:  (&tty->atomic_write_lock){+.+.}, at: [<ffffffff8354be65>] tty_send_xchar+0x1b5/0x360 drivers/tty/tty_io.c:1086
 #2:  (&tty->termios_rwsem){++++}, at: [<ffffffff8354be98>] tty_send_xchar+0x1e8/0x360 drivers/tty/tty_io.c:1089
 #3:  (&(&port->lock)->rlock){-.-.}, at: [<ffffffff83560b1b>] tty_insert_flip_string_and_push_buffer+0x2b/0x160 drivers/tty/tty_buffer.c:569
 #4:  (console_lock){+.+.}, at: [<ffffffff81444378>] vprintk_func+0x58/0x160 kernel/printk/printk_safe.c:409

stack backtrace:
CPU: 1 PID: 7987 Comm: syz-executor406 Not tainted 4.14.305-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x281 lib/dump_stack.c:58
 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1258
 check_prev_add kernel/locking/lockdep.c:1905 [inline]
 check_prevs_add kernel/locking/lockdep.c:2022 [inline]
 validate_chain kernel/locking/lockdep.c:2464 [inline]
 __lock_acquire+0x2e0e/0x3f20 kernel/locking/lockdep.c:3491
 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
 console_lock_spinning_enable kernel/printk/printk.c:1590 [inline]
 console_unlock+0x36f/0xf20 kernel/printk/printk.c:2406
 vprintk_emit+0x224/0x620 kernel/printk/printk.c:1925
 vprintk_func+0x58/0x160 kernel/printk/printk_safe.c:409
 printk+0x9e/0xbc kernel/printk/printk.c:1998
 fail_dump lib/fault-inject.c:44 [inline]
 should_fail.cold+0xdf/0x149 lib/fault-inject.c:149
 should_failslab+0xd6/0x130 mm/failslab.c:32
 slab_pre_alloc_hook mm/slab.h:421 [inline]
 slab_alloc mm/slab.c:3376 [inline]
 __do_kmalloc mm/slab.c:3718 [inline]
 __kmalloc+0x6d/0x400 mm/slab.c:3729
 kmalloc include/linux/slab.h:493 [inline]
 tty_buffer_alloc+0xc0/0x270 drivers/tty/tty_buffer.c:169
 __tty_buffer_request_room+0x12c/0x290 drivers/tty/tty_buffer.c:268
 tty_insert_flip_string_fixed_flag+0x8b/0x210 drivers/tty/tty_buffer.c:313
 tty_insert_flip_string include/linux/tty_flip.h:36 [inline]
 tty_insert_flip_string_and_push_buffer+0x3e/0x160 drivers/tty/tty_buffer.c:570
 pty_write+0xc3/0xf0 drivers/tty/pty.c:118
 tty_send_xchar+0x245/0x360 drivers/tty/tty_io.c:1092
 n_tty_ioctl_helper+0x145/0x350 drivers/tty/tty_ioctl.c:926
 n_tty_ioctl+0x47/0x2e0 drivers/tty/n_tty.c:2466
 tty_ioctl+0x5af/0x1430 drivers/tty/tty_io.c:2670
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:500 [inline]
 do_vfs_ioctl+0x75a/0xff0 fs/ioctl.c:684
 SYSC_ioctl fs/ioctl.c:701 [inline]
 SyS_ioctl+0x7f/0xb0 fs/ioctl.c:692
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x5e/0xd3
RIP: 0033:0x7f6d28001699
RSP: 002b:00007ffcb2860638 EFLAGS: 00000