------------[ cut here ]------------
ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x90 kernel/workqueue.c:1355
WARNING: CPU: 1 PID: 4303 at lib/debugobjects.c:291 debug_print_object+0x166/0x220 lib/debugobjects.c:288
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 4303 Comm: syz-executor6 Not tainted 4.16.0-rc2+ #248
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 panic+0x1e4/0x41c kernel/panic.c:183
 __warn+0x1dc/0x200 kernel/panic.c:547
 report_bug+0x211/0x2d0 lib/bug.c:184
 fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
 fixup_bug arch/x86/kernel/traps.c:247 [inline]
 do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
 invalid_op+0x58/0x80 arch/x86/entry/entry_64.S:957
RIP: 0010:debug_print_object+0x166/0x220 lib/debugobjects.c:288
RSP: 0018:ffff8801c46af790 EFLAGS: 00010082
RAX: dffffc0000000008 RBX: 0000000000000003 RCX: ffffffff815ac30e
RDX: 0000000000000000 RSI: 1ffff100388d5ea2 RDI: 1ffff100388d5e77
RBP: ffff8801c46af7d0 R08: 0000000000000000 R09: 1ffff100388d5e49
R10: ffffed00388d5f21 R11: ffffffff86f395b8 R12: 0000000000000001
R13: ffffffff86f4ae20 R14: ffffffff86407fa0 R15: ffffffff815fed70
 __debug_check_no_obj_freed lib/debugobjects.c:745 [inline]
 debug_check_no_obj_freed+0x662/0xf1f lib/debugobjects.c:774
 __vunmap+0x112/0x380 mm/vmalloc.c:1530
 vfree+0x50/0xe0 mm/vmalloc.c:1606
 copy_entries_to_user net/ipv4/netfilter/arp_tables.c:718 [inline]
 get_entries net/ipv4/netfilter/arp_tables.c:871 [inline]
 do_arpt_get_ctl+0x7c4/0xa00 net/ipv4/netfilter/arp_tables.c:1489
 nf_sockopt net/netfilter/nf_sockopt.c:104 [inline]
 nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122
 ip_getsockopt+0x152/0x200 net/ipv4/ip_sockglue.c:1572
 tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3332
 sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2938
 SYSC_getsockopt net/socket.c:1881 [inline]
 SyS_getsockopt+0x178/0x340 net/socket.c:1863
 do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45683a
RSP: 002b:0000000000a3eb48 EFLAGS: 00000212 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 000000000000042c RCX: 000000000045683a
RDX: 0000000000000061 RSI: 0000000000000000 RDI: 0000000000000013
RBP: 0000000000a3f200 R08: 0000000000a3eb7c R09: 0000000000000001
R10: 0000000000a3f200 R11: 0000000000000212 R12: 0000000000a3eb80
R13: 0000000000000013 R14: 0000000000000000 R15: 0000000000001380

======================================================
WARNING: possible circular locking dependency detected
4.16.0-rc2+ #248 Not tainted
------------------------------------------------------
syz-executor6/4303 is trying to acquire lock:
 ((console_sem).lock){-.-.}, at: [<000000001208181e>] down_trylock+0x13/0x70 kernel/locking/semaphore.c:136

but task is already holding lock:
 (&obj_hash[i].lock){-.-.}, at: [<000000007f69230b>] __debug_check_no_obj_freed lib/debugobjects.c:736 [inline]
 (&obj_hash[i].lock){-.-.}, at: [<000000007f69230b>] debug_check_no_obj_freed+0x1e9/0xf1f lib/debugobjects.c:774

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&obj_hash[i].lock){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
       __debug_object_init+0x109/0x1040 lib/debugobjects.c:343
       debug_object_init+0x17/0x20 lib/debugobjects.c:391
       debug_hrtimer_init kernel/time/hrtimer.c:410 [inline]
       debug_init kernel/time/hrtimer.c:458 [inline]
       hrtimer_init+0x8c/0x410 kernel/time/hrtimer.c:1259
       init_dl_task_timer+0x1b/0x50 kernel/sched/deadline.c:1060
       __sched_fork+0x2bb/0xb60 kernel/sched/core.c:2189
       init_idle+0x75/0x820 kernel/sched/core.c:5352
       sched_init+0xb19/0xc43 kernel/sched/core.c:6049
       start_kernel+0x452/0x819 init/main.c:585
       x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378
       x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359
       secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237

-> #2 (&rq->lock){-.-.}:
       __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
       _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:144
       rq_lock kernel/sched/sched.h:1760 [inline]
       task_fork_fair+0x7a/0x690 kernel/sched/fair.c:9471
       sched_fork+0x450/0xc10 kernel/sched/core.c:2405
       copy_process.part.38+0x1758/0x4b60 kernel/fork.c:1763
       copy_process kernel/fork.c:1606 [inline]
       _do_fork+0x1f7/0xf70 kernel/fork.c:2087
       kernel_thread+0x34/0x40 kernel/fork.c:2146
       rest_init+0x22/0xf0 init/main.c:402
       start_kernel+0x7f1/0x819 init/main.c:716
       x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:378
       x86_64_start_kernel+0x77/0x7a arch/x86/kernel/head64.c:359
       secondary_startup_64+0xa5/0xb0 arch/x86/kernel/head_64.S:237

-> #1 (&p->pi_lock){-.-.}:
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
       try_to_wake_up+0xbc/0x15f0 kernel/sched/core.c:1989
       wake_up_process+0x10/0x20 kernel/sched/core.c:2152
       __up.isra.0+0x1cc/0x2c0 kernel/locking/semaphore.c:262
       up+0x13b/0x1d0 kernel/locking/semaphore.c:187
       __up_console_sem+0xb2/0x1a0 kernel/printk/printk.c:242
       console_unlock+0x5af/0xfb0 kernel/printk/printk.c:2417
       do_con_write+0x106e/0x1f70 drivers/tty/vt/vt.c:2433
       con_write+0x25/0xb0 drivers/tty/vt/vt.c:2782
       process_output_block drivers/tty/n_tty.c:579 [inline]
       n_tty_write+0x5ef/0xec0 drivers/tty/n_tty.c:2302
       do_tty_write drivers/tty/tty_io.c:949 [inline]
       tty_write+0x3fa/0x840 drivers/tty/tty_io.c:1033
       __vfs_write+0xef/0x970 fs/read_write.c:480
       vfs_write+0x189/0x510 fs/read_write.c:544
       SYSC_write fs/read_write.c:589 [inline]
       SyS_write+0xef/0x220 fs/read_write.c:581
       do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #0 ((console_sem).lock){-.-.}:
       lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
       __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
       _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
       down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
       __down_trylock_console_sem+0xa2/0x1e0 kernel/printk/printk.c:225
       console_trylock+0x15/0x70 kernel/printk/printk.c:2229
       console_trylock_spinning kernel/printk/printk.c:1643 [inline]
       vprintk_emit+0x5b5/0xb90 kernel/printk/printk.c:1906
       vprintk_default+0x28/0x30 kernel/printk/printk.c:1947
       vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
       printk+0xaa/0xca kernel/printk/printk.c:1980
       __warn_printk+0x90/0xf0 kernel/panic.c:599
       debug_print_object+0x166/0x220 lib/debugobjects.c:288
       __debug_check_no_obj_freed lib/debugobjects.c:745 [inline]
       debug_check_no_obj_freed+0x662/0xf1f lib/debugobjects.c:774
       __vunmap+0x112/0x380 mm/vmalloc.c:1530
       vfree+0x50/0xe0 mm/vmalloc.c:1606
       copy_entries_to_user net/ipv4/netfilter/arp_tables.c:718 [inline]
       get_entries net/ipv4/netfilter/arp_tables.c:871 [inline]
       do_arpt_get_ctl+0x7c4/0xa00 net/ipv4/netfilter/arp_tables.c:1489
       nf_sockopt net/netfilter/nf_sockopt.c:104 [inline]
       nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122
       ip_getsockopt+0x152/0x200 net/ipv4/ip_sockglue.c:1572
       tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3332
       sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2938
       SYSC_getsockopt net/socket.c:1881 [inline]
       SyS_getsockopt+0x178/0x340 net/socket.c:1863
       do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

other info that might help us debug this:

Chain exists of:
  (console_sem).lock --> &rq->lock --> &obj_hash[i].lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&obj_hash[i].lock);
                               lock(&rq->lock);
                               lock(&obj_hash[i].lock);
  lock((console_sem).lock);

 *** DEADLOCK ***

2 locks held by syz-executor6/4303:
 #0:  (&xt[i].mutex){+.+.}, at: [<00000000709cec9a>] xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1040
 #1:  (&obj_hash[i].lock){-.-.}, at: [<000000007f69230b>] __debug_check_no_obj_freed lib/debugobjects.c:736 [inline]
 #1:  (&obj_hash[i].lock){-.-.}, at: [<000000007f69230b>] debug_check_no_obj_freed+0x1e9/0xf1f lib/debugobjects.c:774

stack backtrace:
CPU: 1 PID: 4303 Comm: syz-executor6 Not tainted 4.16.0-rc2+ #248
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 print_circular_bug.isra.38+0x2cd/0x2dc kernel/locking/lockdep.c:1223
 check_prev_add kernel/locking/lockdep.c:1863 [inline]
 check_prevs_add kernel/locking/lockdep.c:1976 [inline]
 validate_chain kernel/locking/lockdep.c:2417 [inline]
 __lock_acquire+0x30a8/0x3e00 kernel/locking/lockdep.c:3431
 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x96/0xc0 kernel/locking/spinlock.c:152
 down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
 __down_trylock_console_sem+0xa2/0x1e0 kernel/printk/printk.c:225
 console_trylock+0x15/0x70 kernel/printk/printk.c:2229
 console_trylock_spinning kernel/printk/printk.c:1643 [inline]
 vprintk_emit+0x5b5/0xb90 kernel/printk/printk.c:1906
 vprintk_default+0x28/0x30 kernel/printk/printk.c:1947
 vprintk_func+0x57/0xc0 kernel/printk/printk_safe.c:379
 printk+0xaa/0xca kernel/printk/printk.c:1980
 __warn_printk+0x90/0xf0 kernel/panic.c:599
 debug_print_object+0x166/0x220 lib/debugobjects.c:288
 __debug_check_no_obj_freed lib/debugobjects.c:745 [inline]
 debug_check_no_obj_freed+0x662/0xf1f lib/debugobjects.c:774
 __vunmap+0x112/0x380 mm/vmalloc.c:1530
 vfree+0x50/0xe0 mm/vmalloc.c:1606
 copy_entries_to_user net/ipv4/netfilter/arp_tables.c:718 [inline]
 get_entries net/ipv4/netfilter/arp_tables.c:871 [inline]
 do_arpt_get_ctl+0x7c4/0xa00 net/ipv4/netfilter/arp_tables.c:1489
 nf_sockopt net/netfilter/nf_sockopt.c:104 [inline]
 nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122
 ip_getsockopt+0x152/0x200 net/ipv4/ip_sockglue.c:1572
 tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3332
 sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2938
 SYSC_getsockopt net/socket.c:1881 [inline]
 SyS_getsockopt+0x178/0x340 net/socket.c:1863
 do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45683a
RSP: 002b:0000000000a3eb48 EFLAGS: 00000212 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 000000000000042c RCX: 000000000045683a
RDX: 0000000000000061 RSI: 0000000000000000 RDI: 0000000000000013
RBP: 0000000000a3f200 R08: 0000000000a3eb7c R09: 0000000000000001
R10: 0000000000a3f200 R11: 0000000000000212 R12: 0000000000a3eb80
R13: 0000000000000013 R14: 0000000000000000 R15: 0000000000001380
Shutting down cpus with NMI
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..