======================================================
WARNING: possible circular locking dependency detected
5.5.0-rc7-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.0/26655 is trying to acquire lock:
ffffffff89999160 (console_owner){-.-.}, at: console_trylock_spinning kernel/printk/printk.c:1724 [inline]
ffffffff89999160 (console_owner){-.-.}, at: vprintk_emit+0x3fd/0x700 kernel/printk/printk.c:1995

but task is already holding lock:
ffff8880a6407140 (&(&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:287
       tty_port_default_wakeup+0x16/0x40 drivers/tty/tty_port.c:47
       tty_port_tty_wakeup+0x57/0x70 drivers/tty/tty_port.c:387
       uart_write_wakeup+0x46/0x70 drivers/tty/serial/serial_core.c:104
       serial8250_tx_chars+0x495/0xaf0 drivers/tty/serial/8250/8250_port.c:1761
       serial8250_handle_irq.part.0+0x261/0x2b0 drivers/tty/serial/8250/8250_port.c:1834
       serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1820 [inline]
       serial8250_default_handle_irq+0xc0/0x150 drivers/tty/serial/8250/8250_port.c:1850
       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
       native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60
       arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:690
       default_idle_call+0x84/0xb0 kernel/sched/idle.c:94
       cpuidle_idle_call kernel/sched/idle.c:154 [inline]
       do_idle+0x3c8/0x6e0 kernel/sched/idle.c:269
       cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:361
       rest_init+0x23b/0x371 init/main.c:451
       arch_call_rest_init+0xe/0x1b
       start_kernel+0x904/0x943 init/main.c:785
       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

-> #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:3142
       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:2475 [inline]
       check_prevs_add kernel/locking/lockdep.c:2580 [inline]
       validate_chain kernel/locking/lockdep.c:2970 [inline]
       __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3954
       lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4484
       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+0x708/0x852 lib/fault-inject.c:144
       __should_fail_alloc_page mm/page_alloc.c:3343 [inline]
       should_fail_alloc_page+0x50/0x60 mm/page_alloc.c:3380
       prepare_alloc_pages mm/page_alloc.c:4672 [inline]
       __alloc_pages_nodemask+0x1a1/0x910 mm/page_alloc.c:4719
       __alloc_pages include/linux/gfp.h:496 [inline]
       __alloc_pages_node include/linux/gfp.h:509 [inline]
       kmem_getpages mm/slab.c:1367 [inline]
       cache_grow_begin+0x90/0xc60 mm/slab.c:2600
       cache_alloc_refill mm/slab.c:2972 [inline]
       ____cache_alloc mm/slab.c:3055 [inline]
       ____cache_alloc mm/slab.c:3038 [inline]
       __do_cache_alloc mm/slab.c:3277 [inline]
       slab_alloc mm/slab.c:3312 [inline]
       __do_kmalloc mm/slab.c:3654 [inline]
       __kmalloc+0x6b2/0x770 mm/slab.c:3665
       kmalloc include/linux/slab.h:561 [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
       n_tty_write+0xb1d/0x1080 drivers/tty/n_tty.c:2356
       do_tty_write drivers/tty/tty_io.c:962 [inline]
       tty_write+0x496/0x7f0 drivers/tty/tty_io.c:1046
       __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]
       __ia32_sys_write+0x71/0xb0 fs/read_write.c:620
       do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
       do_fast_syscall_32+0x27b/0xe16 arch/x86/entry/common.c:408
       entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

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-executor.0/26655:
 #0: ffff8880914cd090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340
 #1: ffff8880914cd118 (&tty->atomic_write_lock){+.+.}, at: tty_write_lock+0x23/0x90 drivers/tty/tty_io.c:888
 #2: ffff8880914cd2a0 (&o_tty->termios_rwsem/1){++++}, at: n_tty_write+0xe0f/0x1080 drivers/tty/n_tty.c:2378
 #3: ffffc900078c3360 (&ldata->output_lock){+.+.}, at: n_tty_write+0xadd/0x1080 drivers/tty/n_tty.c:2355
 #4: ffff8880a6407140 (&(&port->lock)->rlock){-.-.}, at: pty_write+0xff/0x200 drivers/tty/pty.c:120

stack backtrace:
CPU: 1 PID: 26655 Comm: syz-executor.0 Not tainted 5.5.0-rc7-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:1684
 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1808
 check_prev_add kernel/locking/lockdep.c:2475 [inline]
 check_prevs_add kernel/locking/lockdep.c:2580 [inline]
 validate_chain kernel/locking/lockdep.c:2970 [inline]
 __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3954
 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4484
 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+0x708/0x852 lib/fault-inject.c:144
 __should_fail_alloc_page mm/page_alloc.c:3343 [inline]
 should_fail_alloc_page+0x50/0x60 mm/page_alloc.c:3380
 prepare_alloc_pages mm/page_alloc.c:4672 [inline]
 __alloc_pages_nodemask+0x1a1/0x910 mm/page_alloc.c:4719
 __alloc_pages include/linux/gfp.h:496 [inline]
 __alloc_pages_node include/linux/gfp.h:509 [inline]
 kmem_getpages mm/slab.c:1367 [inline]
 cache_grow_begin+0x90/0xc60 mm/slab.c:2600
 cache_alloc_refill mm/slab.c:2972 [inline]
 ____cache_alloc mm/slab.c:3055 [inline]
 ____cache_alloc mm/slab.c:3038 [inline]
 __do_cache_alloc mm/slab.c:3277 [inline]
 slab_alloc mm/slab.c:3312 [inline]
 __do_kmalloc mm/slab.c:3654 [inline]
 __kmalloc+0x6b2/0x770 mm/slab.c:3665
 kmalloc include/linux/slab.h:561 [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
 n_tty_write+0xb1d/0x1080 drivers/tty/n_tty.c:2356
 do_tty_write drivers/tty/tty_io.c:962 [inline]
 tty_write+0x496/0x7f0 drivers/tty/tty_io.c:1046
 __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]
 __ia32_sys_write+0x71/0xb0 fs/read_write.c:620
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x27b/0xe16 arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f7a9a9
Code: 00 00 00 89 d3 5b 5e 5f 5d c3 b8 80 96 98 00 eb c4 8b 04 24 c3 8b 1c 24 c3 8b 34 24 c3 8b 3c 24 c3 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f5d760cc EFLAGS: 00000296 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000200001c0
RDX: 00000000ffffffde RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000