WARNING: ODEBUG bug in do_ipt_get_ctl

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
91ab883eb21325ad80f3473633f794c78ac87f51 (Mon Feb 19 01:29:42 2018 +0000)
Linux 4.16-rc2

So far this crash happened 2 times on
https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git/master,
net-next.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d7deaf...@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.

IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
------------[ cut here ]------------
ODEBUG: free active (active state 0) object type: work_struct hint:
htable_gc+0x0/0xc0 net/netfilter/xt_hashlimit.c:376
WARNING: CPU: 1 PID: 4157 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: 4157 Comm: syz-executor3 Not tainted 4.16.0-rc2+ #320
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+0x194/0x257 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:ffff8801b7db7778 EFLAGS: 00010082
RAX: dffffc0000000008 RBX: 0000000000000003 RCX: ffffffff815abdbe
RDX: 0000000000000000 RSI: 1ffff10036fb6e9f RDI: 1ffff10036fb6e74
RBP: ffff8801b7db77b8 R08: 0000000000000000 R09: 1ffff10036fb6e46
R10: ffffed0036fb6f1e R11: ffffffff86b394b8 R12: 0000000000000001
R13: ffffffff86b14d80 R14: ffffffff86007de0 R15: ffffffff8147ac00
__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/ip_tables.c:875 [inline]
get_entries net/ipv4/netfilter/ip_tables.c:1030 [inline]
do_ipt_get_ctl+0x7f5/0xac0 net/ipv4/netfilter/ip_tables.c:1703
nf_sockopt net/netfilter/nf_sockopt.c:104 [inline]
nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122
ip_getsockopt+0x15c/0x220 net/ipv4/ip_sockglue.c:1571
tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3359
sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2934
SYSC_getsockopt net/socket.c:1880 [inline]
SyS_getsockopt+0x178/0x340 net/socket.c:1862
do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45687a
RSP: 002b:0000000000a3e3b8 EFLAGS: 00000216 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000a3e3e0 RCX: 000000000045687a
RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00000000006ff880 R08: 0000000000a3e3dc R09: 0000000000004000
R10: 0000000000a3e4e0 R11: 0000000000000216 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00000000006fd6c0

======================================================
WARNING: possible circular locking dependency detected
4.16.0-rc2+ #320 Not tainted
------------------------------------------------------
syz-executor3/4157 is trying to acquire lock:
((console_sem).lock){..-.}, at: [<000000002930b44d>]
down_trylock+0x13/0x70 kernel/locking/semaphore.c:136

but task is already holding lock:
(&obj_hash[i].lock){-.-.}, at: [<000000001f892393>]
__debug_check_no_obj_freed lib/debugobjects.c:736 [inline]
(&obj_hash[i].lock){-.-.}, at: [<000000001f892393>]
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.37+0x1758/0x4b60 kernel/fork.c:1774
copy_process kernel/fork.c:1617 [inline]
_do_fork+0x1f7/0xf70 kernel/fork.c:2098
kernel_thread+0x34/0x40 kernel/fork.c:2157
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/ip_tables.c:875 [inline]
get_entries net/ipv4/netfilter/ip_tables.c:1030 [inline]
do_ipt_get_ctl+0x7f5/0xac0 net/ipv4/netfilter/ip_tables.c:1703
nf_sockopt net/netfilter/nf_sockopt.c:104 [inline]
nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122
ip_getsockopt+0x15c/0x220 net/ipv4/ip_sockglue.c:1571
tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3359
sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2934
SYSC_getsockopt net/socket.c:1880 [inline]
SyS_getsockopt+0x178/0x340 net/socket.c:1862
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 ***

3 locks held by syz-executor3/4157:
#0: (sk_lock-AF_INET){+.+.}, at: [<000000003896cbdb>] lock_sock
include/net/sock.h:1463 [inline]
#0: (sk_lock-AF_INET){+.+.}, at: [<000000003896cbdb>]
ip_getsockopt+0x143/0x220 net/ipv4/ip_sockglue.c:1570
#1: (&xt[i].mutex){+.+.}, at: [<000000002c082b3e>]
xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1046
#2: (&obj_hash[i].lock){-.-.}, at: [<000000001f892393>]
__debug_check_no_obj_freed lib/debugobjects.c:736 [inline]
#2: (&obj_hash[i].lock){-.-.}, at: [<000000001f892393>]
debug_check_no_obj_freed+0x1e9/0xf1f lib/debugobjects.c:774

stack backtrace:
CPU: 1 PID: 4157 Comm: syz-executor3 Not tainted 4.16.0-rc2+ #320
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+0x194/0x257 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/ip_tables.c:875 [inline]
get_entries net/ipv4/netfilter/ip_tables.c:1030 [inline]
do_ipt_get_ctl+0x7f5/0xac0 net/ipv4/netfilter/ip_tables.c:1703
nf_sockopt net/netfilter/nf_sockopt.c:104 [inline]
nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122
ip_getsockopt+0x15c/0x220 net/ipv4/ip_sockglue.c:1571
tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3359
sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2934
SYSC_getsockopt net/socket.c:1880 [inline]
SyS_getsockopt+0x178/0x340 net/socket.c:1862
do_syscall_64+0x280/0x940 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x45687a
RSP: 002b:0000000000a3e3b8 EFLAGS: 00000216 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000a3e3e0 RCX: 000000000045687a
RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00000000006ff880 R08: 0000000000a3e3dc R09: 0000000000004000
R10: 0000000000a3e4e0 R11: 0000000000000216 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00000000006fd6c0
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a dumb bot. It may contain errors.
See https://goo.gl/tpsmEJ for details.
Direct all questions to syzk...@googlegroups.com.

syzbot will keep track of this bug report.
If you forgot to add the Reported-by tag, once the fix for this bug is
merged
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#syz fix: exact-commit-title
If you want to test a patch for this bug, please reply with:
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Note: if the crash happens again, it will cause creation of a new bug
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Note: all commands must start from beginning of the line in the email body.

[syzbot]

syzbot has found reproducer for the following crash on net-next commit
f74290fdb363665538743d14c4f00aeacdb68d87 (Sat Feb 24 05:04:20 2018 +0000)
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

So far this crash happened 3 times on net-next, upstream.
C reproducer is attached.

syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d7deaf...@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed.

------------[ 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: 4244 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: 4244 Comm: syzkaller150583 Not tainted 4.16.0-rc2+ #241

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:ffff8801cc2c7778 EFLAGS: 00010082
RAX: dffffc0000000008 RBX: 0000000000000003 RCX: ffffffff815abe7e
RDX: 0000000000000000 RSI: 1ffff10039858e9f RDI: 1ffff10039858e74
RBP: ffff8801cc2c77b8 R08: 0000000000000000 R09: 1ffff10039858e46
R10: ffffed0039858f1e R11: ffffffff86f395b8 R12: 0000000000000001
R13: ffffffff86f4ae20 R14: ffffffff86407fa0 R15: ffffffff815fe8e0

__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/ip_tables.c:880 [inline]
get_entries net/ipv4/netfilter/ip_tables.c:1035 [inline]
do_ipt_get_ctl+0x7f5/0xac0 net/ipv4/netfilter/ip_tables.c:1708

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: 0033:0x455faa
RSP: 002b:000000000080e8c8 EFLAGS: 00000216 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00000000006ea840 RCX: 0000000000455faa
RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00000000006ea840 R08: 000000000080e8ec R09: 0000000000004000
R10: 000000000080e9f0 R11: 0000000000000216 R12: 0000000000000004
R13: 000000000080e9f0 R14: 000000000080e8f0 R15: 0000000000000000

======================================================
WARNING: possible circular locking dependency detected

4.16.0-rc2+ #241 Not tainted
------------------------------------------------------
syzkaller150583/4244 is trying to acquire lock:
((console_sem).lock){..-.}, at: [<000000003b3aa024>]

down_trylock+0x13/0x70 kernel/locking/semaphore.c:136

but task is already holding lock:

(&obj_hash[i].lock){-.-.}, at: [<00000000e7f32348>]
__debug_check_no_obj_freed lib/debugobjects.c:736 [inline]
(&obj_hash[i].lock){-.-.}, at: [<00000000e7f32348>]

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

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

kauditd_printk_skb kernel/audit.c:506 [inline]
kauditd_hold_skb+0x163/0x180 kernel/audit.c:539
kauditd_send_queue+0xfa/0x140 kernel/audit.c:702
kauditd_thread+0x660/0x940 kernel/audit.c:828
kthread+0x33c/0x400 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:407

-> #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/ip_tables.c:880 [inline]
get_entries net/ipv4/netfilter/ip_tables.c:1035 [inline]
do_ipt_get_ctl+0x7f5/0xac0 net/ipv4/netfilter/ip_tables.c:1708

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 syzkaller150583/4244:
#0: (&xt[i].mutex){+.+.}, at: [<00000000806f2582>]
xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1040
#1: (&obj_hash[i].lock){-.-.}, at: [<00000000e7f32348>]
__debug_check_no_obj_freed lib/debugobjects.c:736 [inline]
#1: (&obj_hash[i].lock){-.-.}, at: [<00000000e7f32348>]

debug_check_no_obj_freed+0x1e9/0xf1f lib/debugobjects.c:774

stack backtrace:

CPU: 1 PID: 4244 Comm: syzkaller150583 Not tainted 4.16.0-rc2+ #241

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/ip_tables.c:880 [inline]
get_entries net/ipv4/netfilter/ip_tables.c:1035 [inline]
do_ipt_get_ctl+0x7f5/0xac0 net/ipv4/netfilter/ip_tables.c:1708

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: 0033:0x455faa
RSP: 002b:000000000080e8c8 EFLAGS: 00000216 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 00000000006ea840 RCX: 0000000000455faa
RDX: 0000000000000041 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00000000006ea840 R08: 000000000080e8ec R09: 0000000000004000
R10: 000000000080e9f0 R11: 0000000000000216 R12: 0000000000000004
R13: 000000000080e9f0 R14: 000000000080e8f0 R15: 0000000000000000

[Eric Biggers]

This last occurred 4 months ago, the report doesn't make sense, and I can't
reproduce it even with the same kernel commit, kernel config, and C repro syzbot
gave. The "debug objects" infrastructure is complaining that there was an
active timer freed by the 'vfree(counters);' in copy_entries_to_user(), via
IPT_SO_GET_ENTRIES. But, 'counters' is simply an array of

struct xt_counters {
__u64 pcnt, bcnt; /* Packet and byte counters */
};

There's no timer it can be freeing.

So I'm invalidating this report, as it probably was a weird bug elsewhere in the
kernel that has been fixed by now.

#syz invalid

- Eric