RBP: 00007ff9aa8511d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffc632ff3df R14: 00007ff9aa851300 R15: 0000000000022000
======================================================
WARNING: possible circular locking dependency detected
5.10.227 #1 Not tainted
------------------------------------------------------
syz-executor.3/6297 is trying to acquire lock:
ffffffff84f0db60 (console_owner){-.-.}-{0:0}, at: console_unlock+0x2e1/0xb40 kernel/printk/printk.c:2513

but task is already holding lock:
ffff888015b96958 (&port->lock){-.-.}-{2:2}, at: tty_insert_flip_string_and_push_buffer+0x2b/0x160 drivers/tty/tty_buffer.c:575

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&port->lock){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x36/0x60 kernel/locking/spinlock.c:159
       tty_port_tty_get+0x1f/0x100 drivers/tty/tty_port.c:289
       tty_port_default_wakeup+0x11/0x40 drivers/tty/tty_port.c:48
       serial8250_tx_chars+0x51f/0xb00 drivers/tty/serial/8250/8250_port.c:1826
       serial8250_handle_irq+0x4e4/0x660 drivers/tty/serial/8250/8250_port.c:1922
       serial8250_default_handle_irq+0x96/0x210 drivers/tty/serial/8250/8250_port.c:1938
       serial8250_interrupt+0xf4/0x1b0 drivers/tty/serial/8250/8250_core.c:127
       __handle_irq_event_percpu+0x2ef/0x6d0 kernel/irq/handle.c:156
       handle_irq_event_percpu kernel/irq/handle.c:196 [inline]
       handle_irq_event+0xff/0x280 kernel/irq/handle.c:213
       handle_edge_irq+0x249/0xd00 kernel/irq/chip.c:819
       run_irq_on_irqstack_cond arch/x86/include/asm/irq_stack.h:103 [inline]
       handle_irq arch/x86/kernel/irq.c:230 [inline]
       __common_interrupt arch/x86/kernel/irq.c:249 [inline]
       common_interrupt+0x94/0x1a0 arch/x86/kernel/irq.c:239
       asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:626
       ffs arch/x86/include/asm/bitops.h:297 [inline]
       __do_softirq+0x173/0x7c9 kernel/softirq.c:286
       asm_call_irq_on_stack+0x12/0x20
       __run_on_irqstack arch/x86/include/asm/irq_stack.h:26 [inline]
       run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:77 [inline]
       do_softirq_own_stack+0x80/0xa0 arch/x86/kernel/irq_64.c:77
       invoke_softirq kernel/softirq.c:393 [inline]
       __irq_exit_rcu kernel/softirq.c:423 [inline]
       irq_exit_rcu+0x114/0x1b0 kernel/softirq.c:435
       sysvec_apic_timer_interrupt+0x43/0xa0 arch/x86/kernel/apic/apic.c:1094
       asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:635
       native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline]
       arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline]
       default_idle+0xe/0x20 arch/x86/kernel/process.c:706
       default_idle_call+0xbf/0x2c0 kernel/sched/idle.c:112
       cpuidle_idle_call kernel/sched/idle.c:194 [inline]
       do_idle+0x3ad/0x520 kernel/sched/idle.c:300
       cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:396
       secondary_startup_64_no_verify+0xbe/0xcb

-> #1 (&port_lock_key){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x36/0x60 kernel/locking/spinlock.c:159
       serial8250_console_write+0x9f5/0xc60 drivers/tty/serial/8250/8250_port.c:3325
       call_console_drivers kernel/printk/printk.c:1917 [inline]
       console_unlock+0x82a/0xb40 kernel/printk/printk.c:2538
       register_console kernel/printk/printk.c:2902 [inline]
       register_console+0x40c/0x850 kernel/printk/printk.c:2802
       univ8250_console_init+0x3a/0x4a drivers/tty/serial/8250/8250_core.c:700
       console_init+0x24c/0x356 kernel/printk/printk.c:3012
       start_kernel+0x2e6/0x489 init/main.c:981
       secondary_startup_64_no_verify+0xbe/0xcb

-> #0 (console_owner){-.-.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:2988 [inline]
       check_prevs_add kernel/locking/lockdep.c:3113 [inline]
       validate_chain kernel/locking/lockdep.c:3729 [inline]
       __lock_acquire+0x29e7/0x5b00 kernel/locking/lockdep.c:4955
       lock_acquire kernel/locking/lockdep.c:5566 [inline]
       lock_acquire+0x197/0x470 kernel/locking/lockdep.c:5531
       console_lock_spinning_enable kernel/printk/printk.c:1763 [inline]
       console_unlock+0x360/0xb40 kernel/printk/printk.c:2535
       vprintk_emit+0x1de/0x4e0 kernel/printk/printk.c:2060
       vprintk_func+0x8b/0x140 kernel/printk/printk_safe.c:401
       printk+0xba/0xf1 kernel/printk/printk.c:2108
       fail_dump lib/fault-inject.c:45 [inline]
       should_fail+0x47a/0x5a0 lib/fault-inject.c:146
       should_failslab+0x5/0x20 mm/slab_common.c:1200
       slab_pre_alloc_hook mm/slab.h:515 [inline]
       slab_alloc_node mm/slub.c:2821 [inline]
       slab_alloc mm/slub.c:2904 [inline]
       __kmalloc+0x72/0x390 mm/slub.c:3967
       kmalloc include/linux/slab.h:557 [inline]
       tty_buffer_alloc+0x243/0x2b0 drivers/tty/tty_buffer.c:175
       __tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:274
       tty_insert_flip_string_fixed_flag+0x91/0x250 drivers/tty/tty_buffer.c:319
       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:576
       pty_write+0xe6/0x110 drivers/tty/pty.c:119
       process_output_block drivers/tty/n_tty.c:591 [inline]
       n_tty_write+0x416/0xfe0 drivers/tty/n_tty.c:2384
       do_tty_write drivers/tty/tty_io.c:1029 [inline]
       file_tty_write.constprop.0+0x529/0x910 drivers/tty/tty_io.c:1119
       call_write_iter include/linux/fs.h:2004 [inline]
       new_sync_write+0x42c/0x660 fs/read_write.c:518
       vfs_write+0x7c0/0xb10 fs/read_write.c:605
       ksys_write+0x12d/0x260 fs/read_write.c:658
       do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x67/0xd1

other info that might help us debug this:

Chain exists of:
  console_owner --> &port_lock_key --> &port->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&port->lock);
                               lock(&port_lock_key);
                               lock(&port->lock);
  lock(console_owner);

 *** DEADLOCK ***

6 locks held by syz-executor.3/6297:
 #0: ffff8880474c4098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x90 drivers/tty/tty_ldisc.c:267
 #1: ffff8880474c4130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:953 [inline]
 #1: ffff8880474c4130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: do_tty_write drivers/tty/tty_io.c:976 [inline]
 #1: ffff8880474c4130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: file_tty_write.constprop.0+0x29f/0x910 drivers/tty/tty_io.c:1119
 #2: ffff8880474c42e8 (&o_tty->termios_rwsem/1){++++}-{3:3}, at: n_tty_write+0x1bf/0xfe0 drivers/tty/n_tty.c:2367
 #3: ffffc90000799378 (&ldata->output_lock){+.+.}-{3:3}, at: process_output_block drivers/tty/n_tty.c:546 [inline]
 #3: ffffc90000799378 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_write+0x542/0xfe0 drivers/tty/n_tty.c:2384
 #4: ffff888015b96958 (&port->lock){-.-.}-{2:2}, at: tty_insert_flip_string_and_push_buffer+0x2b/0x160 drivers/tty/tty_buffer.c:575
 #5: ffffffff84fedee0 (console_lock){+.+.}-{0:0}, at: vprintk_func+0x8b/0x140 kernel/printk/printk_safe.c:401

stack backtrace:
CPU: 1 PID: 6297 Comm: syz-executor.3 Not tainted 5.10.227 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x107/0x167 lib/dump_stack.c:118
 check_noncircular+0x263/0x2e0 kernel/locking/lockdep.c:2123
 check_prev_add kernel/locking/lockdep.c:2988 [inline]
 check_prevs_add kernel/locking/lockdep.c:3113 [inline]
 validate_chain kernel/locking/lockdep.c:3729 [inline]
 __lock_acquire+0x29e7/0x5b00 kernel/locking/lockdep.c:4955
 lock_acquire kernel/locking/lockdep.c:5566 [inline]
 lock_acquire+0x197/0x470 kernel/locking/lockdep.c:5531
 console_lock_spinning_enable kernel/printk/printk.c:1763 [inline]
 console_unlock+0x360/0xb40 kernel/printk/printk.c:2535
 vprintk_emit+0x1de/0x4e0 kernel/printk/printk.c:2060
 vprintk_func+0x8b/0x140 kernel/printk/printk_safe.c:401
 printk+0xba/0xf1 kernel/printk/printk.c:2108
 fail_dump lib/fault-inject.c:45 [inline]
 should_fail+0x47a/0x5a0 lib/fault-inject.c:146
 should_failslab+0x5/0x20 mm/slab_common.c:1200
 slab_pre_alloc_hook mm/slab.h:515 [inline]
 slab_alloc_node mm/slub.c:2821 [inline]
 slab_alloc mm/slub.c:2904 [inline]
 __kmalloc+0x72/0x390 mm/slub.c:3967
 kmalloc include/linux/slab.h:557 [inline]
 tty_buffer_alloc+0x243/0x2b0 drivers/tty/tty_buffer.c:175
 __tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:274
 tty_insert_flip_string_fixed_flag+0x91/0x250 drivers/tty/tty_buffer.c:319
 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:576
 pty_write+0xe6/0x110 drivers/tty/pty.c:119
 process_output_block drivers/tty/n_tty.c:591 [inline]
 n_tty_write+0x416/0xfe0 drivers/tty/n_tty.c:2384
 do_tty_write drivers/tty/tty_io.c:1029 [inline]
 file_tty_write.constprop.0+0x529/0x910 drivers/tty/tty_io.c:1119
 call_write_iter include/linux/fs.h:2004 [inline]
 new_sync_write+0x42c/0x660 fs/read_write.c:518
 vfs_write+0x7c0/0xb10 fs/read_write.c:605
 ksys_write+0x12d/0x260 fs/read_write.c:658
 do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x67/0xd1
RIP: 0033:0x7ff9ad2dbb19
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff9aa851188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ff9ad3eef60 RCX: 00007ff9ad2dbb19
RDX: 00000000000000d8 RSI: 00000000200000c0 RDI: 0000000000000004
RBP: 00007ff9aa8511d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffc632ff3df R14: 00007ff9aa851300 R15: 0000000000022000
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pid=6308 comm=syz-executor.7
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pid=6293 comm=syz-executor.7
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pid=6293 comm=syz-executor.7
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pid=6309 comm=syz-executor.7
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pid=6311 comm=syz-executor.7
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pid=6310 comm=syz-executor.7