WARNING: ODEBUG bug in xt_compat_flush_offsets

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
e64b9562ba281dc1dc613408707375cb9c5660e5 (Sun Mar 4 20:12:48 2018 +0000)
Merge branch 'x86/urgent' of
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.
user-space arch: i386

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4759fb...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for
details.
If you forward the report, please keep this part and the footer.

------------[ 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: 0 PID: 4298 at lib/debugobjects.c:291
debug_print_object+0x166/0x220 lib/debugobjects.c:288
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 4298 Comm: syz-executor0 Not tainted 4.16.0-rc3+ #250
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+0x1b/0x40 arch/x86/entry/entry_64.S:986
RIP: 0010:debug_print_object+0x166/0x220 lib/debugobjects.c:288
RSP: 0018:ffff8801d1caf3b8 EFLAGS: 00010082
RAX: dffffc0000000008 RBX: 0000000000000003 RCX: ffffffff815abb7e
RDX: 0000000000000000 RSI: 1ffff1003a395e27 RDI: 1ffff1003a395dfc
RBP: ffff8801d1caf3f8 R08: 0000000000000000 R09: 1ffff1003a395dce
R10: ffffed003a395ea6 R11: ffffffff86f39838 R12: 0000000000000001
R13: ffffffff86f4b0a0 R14: ffffffff86408340 R15: ffffffff815fe350
__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
xt_compat_flush_offsets+0x68/0x130 net/netfilter/x_tables.c:550
get_info+0x52f/0x690 net/ipv6/netfilter/ip6_tables.c:1002
compat_do_ipt_get_ctl+0x468/0xc00 net/ipv4/netfilter/ip_tables.c:1658
compat_nf_sockopt net/netfilter/nf_sockopt.c:139 [inline]
compat_nf_getsockopt+0x8b/0x130 net/netfilter/nf_sockopt.c:163
compat_ip_getsockopt+0x18a/0x230 net/ipv4/ip_sockglue.c:1602
inet_csk_compat_getsockopt+0x95/0x120 net/ipv4/inet_connection_sock.c:1028
compat_tcp_getsockopt+0x3d/0x70 net/ipv4/tcp.c:3370
compat_sock_common_getsockopt+0xb2/0x140 net/core/sock.c:2945
C_SYSC_getsockopt net/compat.c:523 [inline]
compat_SyS_getsockopt net/compat.c:506 [inline]
C_SYSC_socketcall net/compat.c:857 [inline]
compat_SyS_socketcall+0xe74/0x17c0 net/compat.c:788
do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
do_fast_syscall_32+0x3ec/0xf9f arch/x86/entry/common.c:392
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f13c99
RSP: 002b:000000000844e3e0 EFLAGS: 00000206 ORIG_RAX: 0000000000000066
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 000000000844e3fc
RDX: 000000000844e454 RSI: 000000000844e454 RDI: 000000000844e4a8
RBP: 0000000008119958 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

======================================================
WARNING: possible circular locking dependency detected
4.16.0-rc3+ #250 Not tainted
------------------------------------------------------
syz-executor0/4298 is trying to acquire lock:
((console_sem).lock){-.-.}, at: [<000000005036a971>]
down_trylock+0x13/0x70 kernel/locking/semaphore.c:136

but task is already holding lock:
(&obj_hash[i].lock){-.-.}, at: [<000000002b262d2f>]
__debug_check_no_obj_freed lib/debugobjects.c:736 [inline]
(&obj_hash[i].lock){-.-.}, at: [<000000002b262d2f>]
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:586
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:239

-> #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:403
start_kernel+0x7f1/0x819 init/main.c:717
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:239

-> #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
vprintk_emit+0x5c3/0xb90 kernel/printk/printk.c:1907
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
regdb_fw_cb+0x1d7/0x220 net/wireless/reg.c:886
request_firmware_work_func+0x151/0x2c0
drivers/base/firmware_class.c:1442
process_one_work+0xc47/0x1bb0 kernel/workqueue.c:2113
worker_thread+0x223/0x1990 kernel/workqueue.c:2247
kthread+0x33c/0x400 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:406

-> #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
xt_compat_flush_offsets+0x68/0x130 net/netfilter/x_tables.c:550
get_info+0x52f/0x690 net/ipv6/netfilter/ip6_tables.c:1002
compat_do_ipt_get_ctl+0x468/0xc00 net/ipv4/netfilter/ip_tables.c:1658
compat_nf_sockopt net/netfilter/nf_sockopt.c:139 [inline]
compat_nf_getsockopt+0x8b/0x130 net/netfilter/nf_sockopt.c:163
compat_ip_getsockopt+0x18a/0x230 net/ipv4/ip_sockglue.c:1602
inet_csk_compat_getsockopt+0x95/0x120
net/ipv4/inet_connection_sock.c:1028
compat_tcp_getsockopt+0x3d/0x70 net/ipv4/tcp.c:3370
compat_sock_common_getsockopt+0xb2/0x140 net/core/sock.c:2945
C_SYSC_getsockopt net/compat.c:523 [inline]
compat_SyS_getsockopt net/compat.c:506 [inline]
C_SYSC_socketcall net/compat.c:857 [inline]
compat_SyS_socketcall+0xe74/0x17c0 net/compat.c:788
do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
do_fast_syscall_32+0x3ec/0xf9f arch/x86/entry/common.c:392
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_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 ***

3 locks held by syz-executor0/4298:
#0: (&xt[i].compat_mutex){+.+.}, at: [<000000003ed3dc53>]
xt_compat_lock+0x30/0x40 net/netfilter/x_tables.c:1111
#1: (&xt[i].mutex){+.+.}, at: [<000000002056caa1>]
xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1040
#2: (&obj_hash[i].lock){-.-.}, at: [<000000002b262d2f>]
__debug_check_no_obj_freed lib/debugobjects.c:736 [inline]
#2: (&obj_hash[i].lock){-.-.}, at: [<000000002b262d2f>]
debug_check_no_obj_freed+0x1e9/0xf1f lib/debugobjects.c:774

stack backtrace:
CPU: 0 PID: 4298 Comm: syz-executor0 Not tainted 4.16.0-rc3+ #250
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
xt_compat_flush_offsets+0x68/0x130 net/netfilter/x_tables.c:550
get_info+0x52f/0x690 net/ipv6/netfilter/ip6_tables.c:1002
compat_do_ipt_get_ctl+0x468/0xc00 net/ipv4/netfilter/ip_tables.c:1658
compat_nf_sockopt net/netfilter/nf_sockopt.c:139 [inline]
compat_nf_getsockopt+0x8b/0x130 net/netfilter/nf_sockopt.c:163
compat_ip_getsockopt+0x18a/0x230 net/ipv4/ip_sockglue.c:1602
inet_csk_compat_getsockopt+0x95/0x120 net/ipv4/inet_connection_sock.c:1028
compat_tcp_getsockopt+0x3d/0x70 net/ipv4/tcp.c:3370
compat_sock_common_getsockopt+0xb2/0x140 net/core/sock.c:2945
C_SYSC_getsockopt net/compat.c:523 [inline]
compat_SyS_getsockopt net/compat.c:506 [inline]
C_SYSC_socketcall net/compat.c:857 [inline]
compat_SyS_socketcall+0xe74/0x17c0 net/compat.c:788
do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
do_fast_syscall_32+0x3ec/0xf9f arch/x86/entry/common.c:392
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f13c99
RSP: 002b:000000000844e3e0 EFLAGS: 00000206 ORIG_RAX: 0000000000000066
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 000000000844e3fc
RDX: 000000000844e454 RSI: 000000000844e454 RDI: 000000000844e4a8
RBP: 0000000008119958 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 00000000000000
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.