R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffc2f713f6f R14: 00007ff437d7f300 R15: 0000000000022000
CPU: 0 PID: 5723 Comm: syz-executor.3 Not tainted 5.10.60 #1
======================================================
WARNING: possible circular locking dependency detected
5.10.60 #1 Not tainted
------------------------------------------------------
syz-executor.1/5727 is trying to acquire lock:
ffffffff84d0a920 (console_owner){-.-.}-{0:0}, at: console_unlock+0x2e1/0xb30 kernel/printk/printk.c:2498

but task is already holding lock:
ffff88801e379958 (&port->lock){-.-.}-{2:2}, at: pty_write+0xf4/0x1f0 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}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x36/0x50 kernel/locking/spinlock.c:159
       tty_port_tty_get+0x1f/0x100 drivers/tty/tty_port.c:288
       tty_port_default_wakeup+0x11/0x40 drivers/tty/tty_port.c:47
       serial8250_tx_chars+0x516/0xac0 drivers/tty/serial/8250/8250_port.c:1850
       serial8250_handle_irq.part.0+0x2d9/0x4d0 drivers/tty/serial/8250/8250_port.c:1937
       serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1910 [inline]
       serial8250_default_handle_irq+0xb8/0x230 drivers/tty/serial/8250/8250_port.c:1953
       serial8250_interrupt+0xf4/0x1a0 drivers/tty/serial/8250/8250_core.c:126
       __handle_irq_event_percpu+0x2ef/0x820 kernel/irq/handle.c:156
       handle_irq_event_percpu kernel/irq/handle.c:196 [inline]
       handle_irq_event+0x102/0x290 kernel/irq/handle.c:213
       handle_edge_irq+0x249/0xd00 kernel/irq/chip.c:822
       asm_call_irq_on_stack+0x12/0x20
       __run_irq_on_irqstack arch/x86/include/asm/irq_stack.h:48 [inline]
       run_irq_on_irqstack_cond arch/x86/include/asm/irq_stack.h:101 [inline]
       handle_irq arch/x86/kernel/irq.c:230 [inline]
       __common_interrupt arch/x86/kernel/irq.c:249 [inline]
       common_interrupt+0xdd/0x190 arch/x86/kernel/irq.c:239
       asm_common_interrupt+0x1e/0x40 arch/x86/include/asm/idtentry.h:626
       native_restore_fl arch/x86/include/asm/irqflags.h:41 [inline]
       arch_local_irq_restore arch/x86/include/asm/irqflags.h:84 [inline]
       __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline]
       _raw_spin_unlock_irqrestore+0x25/0x40 kernel/locking/spinlock.c:191
       spin_unlock_irqrestore include/linux/spinlock.h:409 [inline]
       uart_write+0x30b/0x5f0 drivers/tty/serial/serial_core.c:615
       do_output_char+0x5e4/0x860 drivers/tty/n_tty.c:442
       process_output drivers/tty/n_tty.c:509 [inline]
       n_tty_write+0x47c/0xf80 drivers/tty/n_tty.c:2361
       do_tty_write drivers/tty/tty_io.c:1028 [inline]
       file_tty_write.constprop.0+0x4f8/0x8d0 drivers/tty/tty_io.c:1118
       tty_write drivers/tty/tty_io.c:1125 [inline]
       redirected_tty_write drivers/tty/tty_io.c:1147 [inline]
       redirected_tty_write+0xa1/0xc0 drivers/tty/tty_io.c:1128
       call_write_iter include/linux/fs.h:1903 [inline]
       do_iter_readv_writev+0x471/0x750 fs/read_write.c:740
       do_iter_write+0x18d/0x670 fs/read_write.c:866
       vfs_writev+0x1d7/0x620 fs/read_write.c:939
       do_writev+0x139/0x300 fs/read_write.c:982
       do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #1 (&port_lock_key){-.-.}-{2:2}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x36/0x50 kernel/locking/spinlock.c:159
       serial8250_console_write+0x8e2/0xb20 drivers/tty/serial/8250/8250_port.c:3323
       call_console_drivers kernel/printk/printk.c:1909 [inline]
       console_unlock+0x823/0xb30 kernel/printk/printk.c:2523
       register_console kernel/printk/printk.c:2864 [inline]
       register_console+0x523/0x800 kernel/printk/printk.c:2754
       univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:690
       console_init+0x361/0x4fa kernel/printk/printk.c:2974
       start_kernel+0x2ed/0x496 init/main.c:984
       secondary_startup_64_no_verify+0xc2/0xcb

-> #0 (console_owner){-.-.}-{0:0}:
       check_prev_add kernel/locking/lockdep.c:2985 [inline]
       check_prevs_add kernel/locking/lockdep.c:3110 [inline]
       validate_chain kernel/locking/lockdep.c:3725 [inline]
       __lock_acquire+0x29fd/0x5b60 kernel/locking/lockdep.c:4950
       lock_acquire kernel/locking/lockdep.c:5560 [inline]
       lock_acquire+0x197/0x490 kernel/locking/lockdep.c:5525
       console_lock_spinning_enable kernel/printk/printk.c:1761 [inline]
       console_unlock+0x360/0xb30 kernel/printk/printk.c:2520
       vprintk_emit+0x1da/0x4d0 kernel/printk/printk.c:2052
       vprintk_func+0x8b/0x140 kernel/printk/printk_safe.c:401
       printk+0xba/0xed kernel/printk/printk.c:2100
       fail_dump lib/fault-inject.c:45 [inline]
       should_fail+0x470/0x590 lib/fault-inject.c:146
       should_failslab+0x5/0x10 mm/slab_common.c:1193
       slab_pre_alloc_hook mm/slab.h:515 [inline]
       slab_alloc_node mm/slub.c:2814 [inline]
       slab_alloc mm/slub.c:2897 [inline]
       __kmalloc+0x72/0x3e0 mm/slub.c:3958
       kmalloc include/linux/slab.h:557 [inline]
       tty_buffer_alloc+0x23f/0x2a0 drivers/tty/tty_buffer.c:175
       __tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:273
       tty_insert_flip_string_fixed_flag+0x8d/0x250 drivers/tty/tty_buffer.c:318
       tty_insert_flip_string include/linux/tty_flip.h:37 [inline]
       pty_write+0x126/0x1f0 drivers/tty/pty.c:122
       n_tty_write+0xa39/0xf80 drivers/tty/n_tty.c:2372
       do_tty_write drivers/tty/tty_io.c:1028 [inline]
       file_tty_write.constprop.0+0x4f8/0x8d0 drivers/tty/tty_io.c:1118
       call_write_iter include/linux/fs.h:1903 [inline]
       new_sync_write+0x427/0x650 fs/read_write.c:518
       vfs_write+0x759/0xa50 fs/read_write.c:605
       ksys_write+0x12d/0x250 fs/read_write.c:658
       do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
       entry_SYSCALL_64_after_hwframe+0x44/0xa9

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.1/5727:
 #0: ffff888040608098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:266
 #1: ffff888040608130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:952 [inline]
 #1: ffff888040608130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: do_tty_write drivers/tty/tty_io.c:975 [inline]
 #1: ffff888040608130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: file_tty_write.constprop.0+0x29d/0x8d0 drivers/tty/tty_io.c:1118
 #2: ffff8880406082e8 (&tty->termios_rwsem){++++}-{3:3}, at: n_tty_write+0x1bc/0xf80 drivers/tty/n_tty.c:2332
 #3: ffffc9001347d378 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_write+0xa00/0xf80 drivers/tty/n_tty.c:2371
 #4: ffff88801e379958 (&port->lock){-.-.}-{2:2}, at: pty_write+0xf4/0x1f0 drivers/tty/pty.c:120
 #5: ffffffff84deaca0 (console_lock){+.+.}-{0:0}, at: vprintk_func+0x8b/0x140 kernel/printk/printk_safe.c:401

stack backtrace:
CPU: 1 PID: 5727 Comm: syz-executor.1 Not tainted 5.10.60 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:118
 check_noncircular+0x268/0x310 kernel/locking/lockdep.c:2120
 check_prev_add kernel/locking/lockdep.c:2985 [inline]
 check_prevs_add kernel/locking/lockdep.c:3110 [inline]
 validate_chain kernel/locking/lockdep.c:3725 [inline]
 __lock_acquire+0x29fd/0x5b60 kernel/locking/lockdep.c:4950
 lock_acquire kernel/locking/lockdep.c:5560 [inline]
 lock_acquire+0x197/0x490 kernel/locking/lockdep.c:5525
 console_lock_spinning_enable kernel/printk/printk.c:1761 [inline]
 console_unlock+0x360/0xb30 kernel/printk/printk.c:2520
 vprintk_emit+0x1da/0x4d0 kernel/printk/printk.c:2052
 vprintk_func+0x8b/0x140 kernel/printk/printk_safe.c:401
 printk+0xba/0xed kernel/printk/printk.c:2100
 fail_dump lib/fault-inject.c:45 [inline]
 should_fail+0x470/0x590 lib/fault-inject.c:146
 should_failslab+0x5/0x10 mm/slab_common.c:1193
 slab_pre_alloc_hook mm/slab.h:515 [inline]
 slab_alloc_node mm/slub.c:2814 [inline]
 slab_alloc mm/slub.c:2897 [inline]
 __kmalloc+0x72/0x3e0 mm/slub.c:3958
 kmalloc include/linux/slab.h:557 [inline]
 tty_buffer_alloc+0x23f/0x2a0 drivers/tty/tty_buffer.c:175
 __tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:273
 tty_insert_flip_string_fixed_flag+0x8d/0x250 drivers/tty/tty_buffer.c:318
 tty_insert_flip_string include/linux/tty_flip.h:37 [inline]
 pty_write+0x126/0x1f0 drivers/tty/pty.c:122
 n_tty_write+0xa39/0xf80 drivers/tty/n_tty.c:2372
 do_tty_write drivers/tty/tty_io.c:1028 [inline]
 file_tty_write.constprop.0+0x4f8/0x8d0 drivers/tty/tty_io.c:1118
 call_write_iter include/linux/fs.h:1903 [inline]
 new_sync_write+0x427/0x650 fs/read_write.c:518
 vfs_write+0x759/0xa50 fs/read_write.c:605
 ksys_write+0x12d/0x250 fs/read_write.c:658
 do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x466609
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:00007ff437d7f188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 0000000000466609
RDX: 0000000000000178 RSI: 0000000020000740 RDI: 0000000000000003
RBP: 00007ff437d7f1d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffc2f713f6f R14: 00007ff437d7f300 R15: 0000000000022000
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:118
 fail_dump lib/fault-inject.c:52 [inline]
 should_fail.cold+0x5/0xa lib/fault-inject.c:146
 copyin lib/iov_iter.c:155 [inline]
 _copy_from_iter_full+0x1fd/0x920 lib/iov_iter.c:797
 copy_from_iter_full include/linux/uio.h:155 [inline]
 memcpy_from_msg include/linux/skbuff.h:3590 [inline]
 netlink_sendmsg+0x7c6/0xd90 net/netlink/af_netlink.c:1906
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg+0x150/0x190 net/socket.c:671
 ____sys_sendmsg+0x701/0x860 net/socket.c:2340
 ___sys_sendmsg+0xff/0x170 net/socket.c:2394
 __sys_sendmsg+0xe9/0x1b0 net/socket.c:2427
 do_syscall_64+0x33/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x466609
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:00007f0780b03188 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 000000000056bf80 RCX: 0000000000466609
RDX: 0000000000000000 RSI: 0000000020000b40 RDI: 0000000000000004
RBP: 00007f0780b031d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffdd66815ff R14: 00007f0780b03300 R15: 0000000000022000