syzbot

RDX: 0000000000000002 RSI: 000000000000540a RDI: 0000000000000003
RBP: 00007ffe82619260 R08: 0000000000000001 R09: 00007f9204d40031
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000004
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
======================================================
WARNING: possible circular locking dependency detected
4.19.211-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor228/8088 is trying to acquire lock:
00000000136d8a2c (console_owner){....}, at: log_next kernel/printk/printk.c:511 [inline]
00000000136d8a2c (console_owner){....}, at: console_unlock+0x3a9/0x1110 kernel/printk/printk.c:2447

but task is already holding lock:
000000008749073c (&(&port->lock)->rlock){-.-.}, 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)->rlock){-.-.}:
       tty_port_tty_get+0x1d/0x80 drivers/tty/tty_port.c:289
       tty_port_default_wakeup+0x11/0x40 drivers/tty/tty_port.c:47
       serial8250_tx_chars+0x490/0xaf0 drivers/tty/serial/8250/8250_port.c:1813
       serial8250_handle_irq.part.0+0x31f/0x3d0 drivers/tty/serial/8250/8250_port.c:1900
       serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1873 [inline]
       serial8250_default_handle_irq+0xae/0x220 drivers/tty/serial/8250/8250_port.c:1916
       serial8250_interrupt+0x101/0x240 drivers/tty/serial/8250/8250_core.c:125
       __handle_irq_event_percpu+0x27e/0x8e0 kernel/irq/handle.c:149
       handle_irq_event_percpu kernel/irq/handle.c:189 [inline]
       handle_irq_event+0x102/0x290 kernel/irq/handle.c:206
       handle_edge_irq+0x260/0xcf0 kernel/irq/chip.c:800
       generic_handle_irq_desc include/linux/irqdesc.h:155 [inline]
       handle_irq+0x35/0x50 arch/x86/kernel/irq_64.c:87
       do_IRQ+0x93/0x1c0 arch/x86/kernel/irq.c:246
       ret_from_intr+0x0/0x1e
       arch_local_irq_restore arch/x86/include/asm/paravirt.h:789 [inline]
       __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline]
       _raw_spin_unlock_irqrestore+0xa3/0xe0 kernel/locking/spinlock.c:184
       spin_unlock_irqrestore include/linux/spinlock.h:384 [inline]
       uart_write+0x3bb/0x6f0 drivers/tty/serial/serial_core.c:612
       do_output_char+0x5de/0x850 drivers/tty/n_tty.c:445
       process_output drivers/tty/n_tty.c:512 [inline]
       n_tty_write+0x46e/0xff0 drivers/tty/n_tty.c:2343
       do_tty_write drivers/tty/tty_io.c:960 [inline]
       tty_write+0x496/0x810 drivers/tty/tty_io.c:1044
       redirected_tty_write+0xaa/0xb0 drivers/tty/tty_io.c:1065
       do_loop_readv_writev fs/read_write.c:704 [inline]
       do_loop_readv_writev fs/read_write.c:688 [inline]
       do_iter_write+0x461/0x5d0 fs/read_write.c:962
       vfs_writev+0x153/0x2e0 fs/read_write.c:1005
       do_writev+0x136/0x330 fs/read_write.c:1040
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #1 (&port_lock_key){-.-.}:
       serial8250_console_write+0x90e/0xb70 drivers/tty/serial/8250/8250_port.c:3290
       call_console_drivers kernel/printk/printk.c:1764 [inline]
       console_unlock+0xbb6/0x1110 kernel/printk/printk.c:2460
       vprintk_emit+0x2d1/0x740 kernel/printk/printk.c:1965
       vprintk_func+0x79/0x180 kernel/printk/printk_safe.c:405
       printk+0xba/0xed kernel/printk/printk.c:2040
       register_console+0x87f/0xc90 kernel/printk/printk.c:2776
       univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:684
       console_init+0x4cb/0x718 kernel/printk/printk.c:2862
       start_kernel+0x686/0x911 init/main.c:659
       secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #0 (console_owner){....}:
       console_lock_spinning_enable kernel/printk/printk.c:1627 [inline]
       console_unlock+0x411/0x1110 kernel/printk/printk.c:2457
       vprintk_emit+0x2d1/0x740 kernel/printk/printk.c:1965
       vprintk_func+0x79/0x180 kernel/printk/printk_safe.c:405
       printk+0xba/0xed kernel/printk/printk.c:2040
       fail_dump lib/fault-inject.c:44 [inline]
       should_fail+0x66b/0x7b0 lib/fault-inject.c:149
       __should_failslab+0x115/0x180 mm/failslab.c:32
       should_failslab+0x5/0x10 mm/slab_common.c:1590
       slab_pre_alloc_hook mm/slab.h:424 [inline]
       slab_alloc mm/slab.c:3383 [inline]
       __do_kmalloc mm/slab.c:3725 [inline]
       __kmalloc+0x6d/0x3c0 mm/slab.c:3736
       kmalloc include/linux/slab.h:520 [inline]
       tty_buffer_alloc+0x23f/0x2a0 drivers/tty/tty_buffer.c:170
       __tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:268
       tty_insert_flip_string_fixed_flag+0x93/0x250 drivers/tty/tty_buffer.c:313
       tty_insert_flip_string include/linux/tty_flip.h:37 [inline]
       pty_write+0x126/0x1f0 drivers/tty/pty.c:122
       tty_send_xchar+0x28d/0x3b0 drivers/tty/tty_io.c:1093
       n_tty_ioctl_helper+0x18d/0x3a0 drivers/tty/tty_ioctl.c:927
       n_tty_ioctl+0x56/0x360 drivers/tty/n_tty.c:2464
       tty_ioctl+0x65d/0x1630 drivers/tty/tty_io.c:2678
       vfs_ioctl fs/ioctl.c:46 [inline]
       file_ioctl fs/ioctl.c:501 [inline]
       do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
       ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
       __do_sys_ioctl fs/ioctl.c:712 [inline]
       __se_sys_ioctl fs/ioctl.c:710 [inline]
       __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
       do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
       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 ***

5 locks held by syz-executor228/8088:
 #0: 000000006b761e2b (&tty->ldisc_sem){++++}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:272
 #1: 00000000a42c8795 (&tty->atomic_write_lock){+.+.}, at: tty_write_lock drivers/tty/tty_io.c:886 [inline]
 #1: 00000000a42c8795 (&tty->atomic_write_lock){+.+.}, at: tty_send_xchar+0x1d9/0x3b0 drivers/tty/tty_io.c:1087
 #2: 000000008fc8ce07 (&tty->termios_rwsem){++++}, at: tty_send_xchar+0x226/0x3b0 drivers/tty/tty_io.c:1090
 #3: 000000008749073c (&(&port->lock)->rlock){-.-.}, at: pty_write+0xf4/0x1f0 drivers/tty/pty.c:120
 #4: 00000000551a309e (console_lock){+.+.}, at: vprintk_func+0x79/0x180 kernel/printk/printk_safe.c:405

stack backtrace:
CPU: 0 PID: 8088 Comm: syz-executor228 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
 print_circular_bug.constprop.0.cold+0x2d7/0x41e kernel/locking/lockdep.c:1222
 check_prev_add kernel/locking/lockdep.c:1866 [inline]
 check_prevs_add kernel/locking/lockdep.c:1979 [inline]
 validate_chain kernel/locking/lockdep.c:2420 [inline]
 __lock_acquire+0x30c9/0x3ff0 kernel/locking/lockdep.c:3416
 lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
 console_lock_spinning_enable kernel/printk/printk.c:1627 [inline]
 console_unlock+0x411/0x1110 kernel/printk/printk.c:2457
 vprintk_emit+0x2d1/0x740 kernel/printk/printk.c:1965
 vprintk_func+0x79/0x180 kernel/printk/printk_safe.c:405
 printk+0xba/0xed kernel/printk/printk.c:2040
 fail_dump lib/fault-inject.c:44 [inline]
 should_fail+0x66b/0x7b0 lib/fault-inject.c:149
 __should_failslab+0x115/0x180 mm/failslab.c:32
 should_failslab+0x5/0x10 mm/slab_common.c:1590
 slab_pre_alloc_hook mm/slab.h:424 [inline]
 slab_alloc mm/slab.c:3383 [inline]
 __do_kmalloc mm/slab.c:3725 [inline]
 __kmalloc+0x6d/0x3c0 mm/slab.c:3736
 kmalloc include/linux/slab.h:520 [inline]
 tty_buffer_alloc+0x23f/0x2a0 drivers/tty/tty_buffer.c:170
 __tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:268
 tty_insert_flip_string_fixed_flag+0x93/0x250 drivers/tty/tty_buffer.c:313
 tty_insert_flip_string include/linux/tty_flip.h:37 [inline]
 pty_write+0x126/0x1f0 drivers/tty/pty.c:122
 tty_send_xchar+0x28d/0x3b0 drivers/tty/tty_io.c:1093
 n_tty_ioctl_helper+0x18d/0x3a0 drivers/tty/tty_ioctl.c:927
 n_tty_ioctl+0x56/0x360 drivers/tty/n_tty.c:2464
 tty_ioctl+0x65d/0x1630 drivers/tty/tty_io.c:2678
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0xcdb/0x12e0 fs/ioctl.c:688
 ksys_ioctl+0x9b/0xc0 fs/ioctl.c:705
 __do_sys_ioctl fs/ioctl.c:712 [inline]
 __se_sys_ioctl fs/ioctl.c:710 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:710
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f9204d80699
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe82619258 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00