WARNING: ODEBUG bug in netdev_freemem

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: fc2fd5f0f1aa Merge branch 'x86-platform-for-linus' of git:..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=172a9e53400000
kernel config: https://syzkaller.appspot.com/x/.config?x=9a98287508be3ff9
dashboard link: https://syzkaller.appspot.com/bug?extid=979ffc89b87309b1b94b
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+979ffc...@syzkaller.appspotmail.com

bond0 (unregistering): Releasing backup interface bond_slave_1
bond0 (unregistering): Releasing backup interface bond_slave_0
bond0 (unregistering): Released all slaves
------------[ cut here ]------------
ODEBUG: free active (active state 0) object type: timer_list hint:
delayed_work_timer_fn+0x0/0x90 kernel/workqueue.c:4916
WARNING: CPU: 1 PID: 26336 at lib/debugobjects.c:328
debug_print_object+0x16a/0x210 lib/debugobjects.c:325
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 26336 Comm: kworker/u4:3 Not tainted 4.20.0+ #391
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1d3/0x2c6 lib/dump_stack.c:113
panic+0x2ad/0x55c kernel/panic.c:188
__warn.cold.8+0x20/0x45 kernel/panic.c:540
report_bug+0x254/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:debug_print_object+0x16a/0x210 lib/debugobjects.c:325
Code: 80 88 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 92 00 00 00 48 8b 14 dd
a0 f1 80 88 4c 89 fe 48 c7 c7 40 e7 80 88 e8 76 ea b8 fd <0f> 0b 83 05 01
3b a7 06 01 48 83 c4 18 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffff888026fdee48 EFLAGS: 00010086
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8165c255 RDI: 0000000000000005
RBP: ffff888026fdee88 R08: ffff888027f762c0 R09: ffffed1015ce3ef8
R10: ffffed1015ce3ef8 R11: ffff8880ae71f7c7 R12: 0000000000000001
R13: ffffffff897a5ce0 R14: ffffffff816c1a80 R15: ffffffff8880ebe0
__debug_check_no_obj_freed lib/debugobjects.c:785 [inline]
debug_check_no_obj_freed+0x3ae/0x58d lib/debugobjects.c:817
kfree+0xbd/0x230 mm/slab.c:3816
kvfree+0x61/0x70 mm/util.c:445
netdev_freemem+0x4c/0x60 net/core/dev.c:8903
netdev_release+0x121/0x180 net/core/net-sysfs.c:1640
device_release+0x7e/0x210 drivers/base/core.c:912
kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]
kref_put include/linux/kref.h:70 [inline]
kobject_put.cold.9+0x287/0x2e4 lib/kobject.c:708
netdev_run_todo+0x715/0xa60 net/core/dev.c:8808
rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:117
default_device_exit_batch+0x43f/0x540 net/core/dev.c:9589
ops_exit_list.isra.5+0x105/0x160 net/core/net_namespace.c:156
cleanup_net+0x555/0xb10 net/core/net_namespace.c:551
process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153
worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
kthread+0x35a/0x440 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

======================================================
WARNING: possible circular locking dependency detected
4.20.0+ #391 Not tainted
------------------------------------------------------
kworker/u4:3/26336 is trying to acquire lock:
00000000d2979eea ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70
kernel/locking/semaphore.c:136

but task is already holding lock:
000000002d00477d (&obj_hash[i].lock){-.-.}, at: __debug_check_no_obj_freed
lib/debugobjects.c:776 [inline]
000000002d00477d (&obj_hash[i].lock){-.-.}, at:
debug_check_no_obj_freed+0x17a/0x58d lib/debugobjects.c:817

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+0x99/0xd0 kernel/locking/spinlock.c:152
__debug_object_init+0x127/0x1290 lib/debugobjects.c:383
debug_object_init+0x16/0x20 lib/debugobjects.c:431
debug_hrtimer_init kernel/time/hrtimer.c:401 [inline]
debug_init kernel/time/hrtimer.c:449 [inline]
hrtimer_init+0x97/0x490 kernel/time/hrtimer.c:1299
init_dl_task_timer+0x1b/0x50 kernel/sched/deadline.c:1057
__sched_fork+0x2ae/0x590 kernel/sched/core.c:2166
init_idle+0x75/0x6d0 kernel/sched/core.c:5374
sched_init+0xb33/0xc07 kernel/sched/core.c:6063
start_kernel+0x448/0x8ae init/main.c:608
x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #2 (&rq->lock){-.-.}:
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
_raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
rq_lock kernel/sched/sched.h:1149 [inline]
task_fork_fair+0xb0/0x6d0 kernel/sched/fair.c:10083
sched_fork+0x443/0xba0 kernel/sched/core.c:2359
copy_process+0x25b9/0x8790 kernel/fork.c:1892
_do_fork+0x1cb/0x11d0 kernel/fork.c:2221
kernel_thread+0x34/0x40 kernel/fork.c:2280
rest_init+0x28/0x372 init/main.c:409
arch_call_rest_init+0xe/0x1b
start_kernel+0x873/0x8ae init/main.c:741
x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #1 (&p->pi_lock){-.-.}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
try_to_wake_up+0xdc/0x1460 kernel/sched/core.c:1965
wake_up_process+0x10/0x20 kernel/sched/core.c:2129
__up.isra.1+0x1c0/0x2a0 kernel/locking/semaphore.c:262
up+0x13c/0x1c0 kernel/locking/semaphore.c:187
__up_console_sem+0xbe/0x1b0 kernel/printk/printk.c:236
console_unlock+0x811/0x1180 kernel/printk/printk.c:2432
vprintk_emit+0x39c/0x990 kernel/printk/printk.c:1922
vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
printk+0xa7/0xcf kernel/printk/printk.c:1997
check_stack_usage kernel/exit.c:755 [inline]
do_exit.cold.19+0x57/0x16f kernel/exit.c:916
do_group_exit+0x177/0x440 kernel/exit.c:970
__do_sys_exit_group kernel/exit.c:981 [inline]
__se_sys_exit_group kernel/exit.c:979 [inline]
__x64_sys_exit_group+0x3e/0x50 kernel/exit.c:979
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 ((console_sem).lock){-.-.}:
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3841
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
__down_trylock_console_sem+0xae/0x200 kernel/printk/printk.c:219
console_trylock+0x15/0xa0 kernel/printk/printk.c:2247
console_trylock_spinning kernel/printk/printk.c:1653 [inline]
vprintk_emit+0x37d/0x990 kernel/printk/printk.c:1921
vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
printk+0xa7/0xcf kernel/printk/printk.c:1997
__warn_printk+0x8c/0xe0 kernel/panic.c:594
debug_print_object+0x16a/0x210 lib/debugobjects.c:325
__debug_check_no_obj_freed lib/debugobjects.c:785 [inline]
debug_check_no_obj_freed+0x3ae/0x58d lib/debugobjects.c:817
kfree+0xbd/0x230 mm/slab.c:3816
kvfree+0x61/0x70 mm/util.c:445
netdev_freemem+0x4c/0x60 net/core/dev.c:8903
netdev_release+0x121/0x180 net/core/net-sysfs.c:1640
device_release+0x7e/0x210 drivers/base/core.c:912
kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]
kref_put include/linux/kref.h:70 [inline]
kobject_put.cold.9+0x287/0x2e4 lib/kobject.c:708
netdev_run_todo+0x715/0xa60 net/core/dev.c:8808
rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:117
default_device_exit_batch+0x43f/0x540 net/core/dev.c:9589
ops_exit_list.isra.5+0x105/0x160 net/core/net_namespace.c:156
cleanup_net+0x555/0xb10 net/core/net_namespace.c:551
process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153
worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
kthread+0x35a/0x440 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

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 ***

4 locks held by kworker/u4:3/26336:
#0: 0000000078b99b2d ((wq_completion)"%s""netns"){+.+.}, at:
__write_once_size include/linux/compiler.h:218 [inline]
#0: 0000000078b99b2d ((wq_completion)"%s""netns"){+.+.}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 0000000078b99b2d ((wq_completion)"%s""netns"){+.+.}, at: atomic64_set
include/asm-generic/atomic-instrumented.h:40 [inline]
#0: 0000000078b99b2d ((wq_completion)"%s""netns"){+.+.}, at:
atomic_long_set include/asm-generic/atomic-long.h:59 [inline]
#0: 0000000078b99b2d ((wq_completion)"%s""netns"){+.+.}, at: set_work_data
kernel/workqueue.c:617 [inline]
#0: 0000000078b99b2d ((wq_completion)"%s""netns"){+.+.}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: 0000000078b99b2d ((wq_completion)"%s""netns"){+.+.}, at:
process_one_work+0xb43/0x1c40 kernel/workqueue.c:2124
#1: 00000000220ca606 (net_cleanup_work){+.+.}, at:
process_one_work+0xb9a/0x1c40 kernel/workqueue.c:2128
#2: 00000000e946b6ef (pernet_ops_rwsem){++++}, at: cleanup_net+0x13f/0xb10
net/core/net_namespace.c:518
#3: 000000002d00477d (&obj_hash[i].lock){-.-.}, at:
__debug_check_no_obj_freed lib/debugobjects.c:776 [inline]
#3: 000000002d00477d (&obj_hash[i].lock){-.-.}, at:
debug_check_no_obj_freed+0x17a/0x58d lib/debugobjects.c:817

stack backtrace:
CPU: 1 PID: 26336 Comm: kworker/u4:3 Not tainted 4.20.0+ #391
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1d3/0x2c6 lib/dump_stack.c:113
print_circular_bug.isra.34.cold.56+0x1bd/0x27d
kernel/locking/lockdep.c:1224
check_prev_add kernel/locking/lockdep.c:1866 [inline]
check_prevs_add kernel/locking/lockdep.c:1979 [inline]
validate_chain kernel/locking/lockdep.c:2350 [inline]
__lock_acquire+0x3360/0x4c20 kernel/locking/lockdep.c:3338
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3841
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
__down_trylock_console_sem+0xae/0x200 kernel/printk/printk.c:219
console_trylock+0x15/0xa0 kernel/printk/printk.c:2247
console_trylock_spinning kernel/printk/printk.c:1653 [inline]
vprintk_emit+0x37d/0x990 kernel/printk/printk.c:1921
vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
printk+0xa7/0xcf kernel/printk/printk.c:1997
__warn_printk+0x8c/0xe0 kernel/panic.c:594
debug_print_object+0x16a/0x210 lib/debugobjects.c:325
__debug_check_no_obj_freed lib/debugobjects.c:785 [inline]
debug_check_no_obj_freed+0x3ae/0x58d lib/debugobjects.c:817
kfree+0xbd/0x230 mm/slab.c:3816
kvfree+0x61/0x70 mm/util.c:445
netdev_freemem+0x4c/0x60 net/core/dev.c:8903
netdev_release+0x121/0x180 net/core/net-sysfs.c:1640
device_release+0x7e/0x210 drivers/base/core.c:912
kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]
kref_put include/linux/kref.h:70 [inline]
kobject_put.cold.9+0x287/0x2e4 lib/kobject.c:708
netdev_run_todo+0x715/0xa60 net/core/dev.c:8808
rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:117
default_device_exit_batch+0x43f/0x540 net/core/dev.c:9589
ops_exit_list.isra.5+0x105/0x160 net/core/net_namespace.c:156
cleanup_net+0x555/0xb10 net/core/net_namespace.c:551
process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153
worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
? trace_hardirqs_on+
Lost 11 message(s)!
Shutting down cpus with NMI
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 28e8c4bc8eb4 Merge tag 'rtc-4.21' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1745f5bf400000
kernel config: https://syzkaller.appspot.com/x/.config?x=c2ab9708c613a224
dashboard link: https://syzkaller.appspot.com/bug?extid=979ffc89b87309b1b94b
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17a93c4b400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+979ffc...@syzkaller.appspotmail.com

bond0 (unregistering): Released all slaves
IPVS: ftp: loaded support on port[0] = 21

------------[ cut here ]------------
ODEBUG: free active (active state 0) object type: timer_list hint:
delayed_work_timer_fn+0x0/0x90 kernel/workqueue.c:4916

kobject: 'lo' (00000000c9c1b9e0): kobject_add_internal: parent: 'net',
set: 'devices'
WARNING: CPU: 1 PID: 9386 at lib/debugobjects.c:325
debug_print_object+0x16a/0x250 lib/debugobjects.c:325
kobject: 'loop1' (000000000c184f51): kobject_uevent_env

Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 9386 Comm: kworker/u4:6 Not tainted 4.20.0+ #4
kobject: 'lo' (00000000c9c1b9e0): kobject_uevent_env

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:

kobject: 'loop1' (000000000c184f51): fill_kobj_path: path
= '/devices/virtual/block/loop1'
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
panic+0x2cb/0x589 kernel/panic.c:189
kobject: 'lo' (00000000c9c1b9e0): fill_kobj_path: path
= '/devices/virtual/net/lo'
kobject: 'queues' (00000000cd7bde5f): kobject_add_internal: parent: 'lo',
set: '<NULL>'
__warn.cold+0x20/0x4b kernel/panic.c:544
report_bug+0x263/0x2b0 lib/bug.c:186
kobject: 'loop1' (000000000c184f51): kobject_uevent_env
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
kobject: 'loop1' (000000000c184f51): fill_kobj_path: path
= '/devices/virtual/block/loop1'
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:290
kobject: 'queues' (00000000cd7bde5f): kobject_uevent_env
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:debug_print_object+0x16a/0x250 lib/debugobjects.c:325
Code: dd c0 46 81 88 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 b5 00 00 00 48
8b 14 dd c0 46 81 88 48 c7 c7 60 3c 81 88 e8 06 22 bb fd <0f> 0b 83 05 01
85 cb 06 01 48 83 c4 20 5b 41 5c 41 5d 41 5e 5d c3
RSP: 0018:ffff8880a3ac7270 EFLAGS: 00010086

RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000

RDX: 0000000000000000 RSI: ffffffff8167d666 RDI: 0000000000000005
RBP: ffff8880a3ac72b0 R08: ffff88807a33a040 R09: ffffed1015ce3ef9

R10: ffffed1015ce3ef8 R11: ffff8880ae71f7c7 R12: 0000000000000001

R13: ffffffff899a8e20 R14: ffffffff816e2a80 R15: dffffc0000000000
kobject: 'queues' (00000000cd7bde5f): kobject_uevent_env: filter function
caused the event to drop!
kobject: 'rx-0' (000000001770de44): kobject_add_internal: parent: 'queues',
set: 'queues'
__debug_check_no_obj_freed lib/debugobjects.c:785 [inline]
debug_check_no_obj_freed+0x39d/0x588 lib/debugobjects.c:817
kobject: 'rx-0' (000000001770de44): kobject_uevent_env
kfree+0xbd/0x230 mm/slab.c:3803
kvfree+0x61/0x70 mm/util.c:445
netdev_freemem+0x4c/0x60 net/core/dev.c:8991
netdev_release+0x119/0x180 net/core/net-sysfs.c:1640
kobject: 'rx-0' (000000001770de44): fill_kobj_path: path
= '/devices/virtual/net/lo/queues/rx-0'
device_release+0x7d/0x210 drivers/base/core.c:919

kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]

kref_put include/linux/kref.h:67 [inline]
kobject_put.cold+0x28f/0x2ec lib/kobject.c:708
netdev_run_todo+0x704/0xae0 net/core/dev.c:8896
kobject: 'loop3' (0000000021871ddf): kobject_uevent_env
rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:117
default_device_exit_batch+0x4d3/0x5f0 net/core/dev.c:9677
ops_exit_list.isra.0+0x105/0x160 net/core/net_namespace.c:156
cleanup_net+0x51d/0xb10 net/core/net_namespace.c:551
process_one_work+0xd0c/0x1ce0 kernel/workqueue.c:2153
worker_thread+0x143/0x14a0 kernel/workqueue.c:2296
kthread+0x357/0x430 kernel/kthread.c:246

ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

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

4.20.0+ #4 Not tainted
------------------------------------------------------
kworker/u4:6/9386 is trying to acquire lock:
000000001121b7cd ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70

kernel/locking/semaphore.c:136

but task is already holding lock:

000000005012344f (&obj_hash[i].lock){-.-.}, at: __debug_check_no_obj_freed
lib/debugobjects.c:776 [inline]
000000005012344f (&obj_hash[i].lock){-.-.}, at:
debug_check_no_obj_freed+0x170/0x588 lib/debugobjects.c:817

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+0x95/0xcd kernel/locking/spinlock.c:152
__debug_object_init+0xf6/0x12d0 lib/debugobjects.c:383

debug_object_init+0x16/0x20 lib/debugobjects.c:431
debug_hrtimer_init kernel/time/hrtimer.c:401 [inline]
debug_init kernel/time/hrtimer.c:449 [inline]

hrtimer_init+0x97/0x480 kernel/time/hrtimer.c:1299
init_dl_task_timer+0x1b/0x50 kernel/sched/deadline.c:1057
__sched_fork+0x2bf/0x5b0 kernel/sched/core.c:2166
init_idle+0x75/0x670 kernel/sched/core.c:5374
sched_init+0xb10/0xbe8 kernel/sched/core.c:6063
start_kernel+0x445/0x8bd init/main.c:609
x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451

secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #2 (&rq->lock){-.-.}:
__raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]

_raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:144
rq_lock kernel/sched/sched.h:1149 [inline]
task_fork_fair+0xb5/0x7a0 kernel/sched/fair.c:10058
sched_fork+0x437/0xb90 kernel/sched/core.c:2359
copy_process+0x1ff6/0x8730 kernel/fork.c:1893
_do_fork+0x1a9/0x1170 kernel/fork.c:2222
kernel_thread+0x34/0x40 kernel/fork.c:2281
rest_init+0x28/0x37b init/main.c:409
arch_call_rest_init+0xe/0x1b
start_kernel+0x882/0x8bd init/main.c:741
x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:470
x86_64_start_kernel+0x77/0x7b arch/x86/kernel/head64.c:451

secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

-> #1 (&p->pi_lock){-.-.}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]

_raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
try_to_wake_up+0xb9/0x1480 kernel/sched/core.c:1965
wake_up_process+0x10/0x20 kernel/sched/core.c:2129
__up.isra.0+0x1c0/0x2a0 kernel/locking/semaphore.c:262
up+0x13e/0x1c0 kernel/locking/semaphore.c:187
__up_console_sem+0xb7/0x1c0 kernel/printk/printk.c:236
console_unlock+0x778/0x11e0 kernel/printk/printk.c:2426
do_con_write+0x1021/0x2420 drivers/tty/vt/vt.c:2767
con_write+0x27/0xb0 drivers/tty/vt/vt.c:3116
process_output_block drivers/tty/n_tty.c:593 [inline]
n_tty_write+0x497/0x1220 drivers/tty/n_tty.c:2331
do_tty_write drivers/tty/tty_io.c:959 [inline]
tty_write+0x45b/0x7a0 drivers/tty/tty_io.c:1043
__vfs_write+0x116/0xb40 fs/read_write.c:485
vfs_write+0x20c/0x580 fs/read_write.c:549
ksys_write+0x105/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:607
do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290

entry_SYSCALL_64_after_hwframe+0x49/0xbe

-> #0 ((console_sem).lock){-.-.}:

lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
__down_trylock_console_sem+0xa8/0x210 kernel/printk/printk.c:219
console_trylock+0x15/0xa0 kernel/printk/printk.c:2242
console_trylock_spinning kernel/printk/printk.c:1662 [inline]
vprintk_emit+0x351/0x960 kernel/printk/printk.c:1930
vprintk_default+0x28/0x30 kernel/printk/printk.c:1958
vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
printk+0xba/0xed kernel/printk/printk.c:1991
__warn_printk+0x9c/0x100 kernel/panic.c:598
debug_print_object+0x16a/0x250 lib/debugobjects.c:325
__debug_check_no_obj_freed lib/debugobjects.c:785 [inline]
debug_check_no_obj_freed+0x39d/0x588 lib/debugobjects.c:817
kfree+0xbd/0x230 mm/slab.c:3803
kvfree+0x61/0x70 mm/util.c:445
netdev_freemem+0x4c/0x60 net/core/dev.c:8991
netdev_release+0x119/0x180 net/core/net-sysfs.c:1640
device_release+0x7d/0x210 drivers/base/core.c:919

kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]

kref_put include/linux/kref.h:67 [inline]
kobject_put.cold+0x28f/0x2ec lib/kobject.c:708
netdev_run_todo+0x704/0xae0 net/core/dev.c:8896
rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:117
default_device_exit_batch+0x4d3/0x5f0 net/core/dev.c:9677
ops_exit_list.isra.0+0x105/0x160 net/core/net_namespace.c:156
cleanup_net+0x51d/0xb10 net/core/net_namespace.c:551
process_one_work+0xd0c/0x1ce0 kernel/workqueue.c:2153
worker_thread+0x143/0x14a0 kernel/workqueue.c:2296
kthread+0x357/0x430 kernel/kthread.c:246

ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

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 ***

4 locks held by kworker/u4:6/9386:
#0: 0000000040aa4f0f ((wq_completion)"%s""netns"){+.+.}, at:
__write_once_size include/linux/compiler.h:218 [inline]
#0: 0000000040aa4f0f ((wq_completion)"%s""netns"){+.+.}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 0000000040aa4f0f ((wq_completion)"%s""netns"){+.+.}, at: atomic64_set
include/asm-generic/atomic-instrumented.h:40 [inline]
#0: 0000000040aa4f0f ((wq_completion)"%s""netns"){+.+.}, at:
atomic_long_set include/asm-generic/atomic-long.h:59 [inline]
#0: 0000000040aa4f0f ((wq_completion)"%s""netns"){+.+.}, at: set_work_data
kernel/workqueue.c:617 [inline]
#0: 0000000040aa4f0f ((wq_completion)"%s""netns"){+.+.}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: 0000000040aa4f0f ((wq_completion)"%s""netns"){+.+.}, at:
process_one_work+0xbc7/0x1ce0 kernel/workqueue.c:2124
#1: 000000006ce09174 (net_cleanup_work){+.+.}, at:
process_one_work+0xc1d/0x1ce0 kernel/workqueue.c:2128
#2: 00000000fe168da9 (pernet_ops_rwsem){++++}, at: cleanup_net+0x126/0xb10
net/core/net_namespace.c:518
#3: 000000005012344f (&obj_hash[i].lock){-.-.}, at:
__debug_check_no_obj_freed lib/debugobjects.c:776 [inline]
#3: 000000005012344f (&obj_hash[i].lock){-.-.}, at:
debug_check_no_obj_freed+0x170/0x588 lib/debugobjects.c:817

stack backtrace:
CPU: 1 PID: 9386 Comm: kworker/u4:6 Not tainted 4.20.0+ #4

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]

dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1224

check_prev_add kernel/locking/lockdep.c:1866 [inline]
check_prevs_add kernel/locking/lockdep.c:1979 [inline]
validate_chain kernel/locking/lockdep.c:2350 [inline]

__lock_acquire+0x3014/0x4a30 kernel/locking/lockdep.c:3338
lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x95/0xcd kernel/locking/spinlock.c:152
down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
__down_trylock_console_sem+0xa8/0x210 kernel/printk/printk.c:219
console_trylock+0x15/0xa0 kernel/printk/printk.c:2242
console_trylock_spinning kernel/printk/printk.c:1662 [inline]
vprintk_emit+0x351/0x960 kernel/printk/printk.c:1930
vprintk_default+0x28/0x30 kernel/printk/printk.c:1958
vprintk_func+0x7e/0x189 kernel/printk/printk_safe.c:398
printk+0xba/0xed kernel/printk/printk.c:1991
__warn_printk+0x9c/0x100 kernel/panic.c:598
debug_print_object+0x16a/0x250 lib/debugobjects.c:325
__debug_check_no_obj_freed lib/debugobjects.c:785 [inline]
debug_check_no_obj_freed+0x39d/0x588 lib/debugobjects.c:817
kfree+0xbd/0x230 mm/slab.c:3803
kvfree+0x61/0x70 mm/util.c:445
netdev_freemem+0x4c/0x60 net/core/dev.c:8991
netdev_release+0x119/0x180 net/core/net-sysfs.c:1640
device_release+0x7d/0x210 drivers/base/core.c:919

kobject_cleanup lib/kobject.c:662 [inline]
kobject_release lib/kobject.c:691 [inline]

kref_put include/linux/kref.h:67 [inline]
kobject_put.cold+0x28f/0x2ec lib/kobject.c:708
netdev_run_todo+0x704/0xae0 net/core/dev.c:8896
rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:117
default_device_exit_batch+0x4d3/0x5f0 net/core/dev.c:9677
ops_exit_list.isra.0+0x105/0x160 net/core/net_namespace.c:156
cleanup_net+0x51d/0xb10 net/core/net_namespace.c:551
process_one_work+0xd0c/0x1ce0 kernel/workqueue.c:2153
worker_thread+0x143/0x14a0 kernel/workqueue.c:2296
kthread+0x357/0x430 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

[syzbot]

syzbot has bisected this bug to:

commit 96e5da7c842424bcf64afe1082b960b42b96190b
Author: Dmitry Osipenko <dig...@gmail.com>
Date: Sun Oct 21 18:30:52 2018 +0000

memory: tegra: Introduce Tegra20 EMC driver

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=14450b93200000
start commit: 28e8c4bc Merge tag 'rtc-4.21' of git://git.kernel.org/pub/..
git tree: upstream
final crash: https://syzkaller.appspot.com/x/report.txt?x=16450b93200000
console output: https://syzkaller.appspot.com/x/log.txt?x=12450b93200000

kernel config: https://syzkaller.appspot.com/x/.config?x=c2ab9708c613a224
dashboard link: https://syzkaller.appspot.com/bug?extid=979ffc89b87309b1b94b

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17a93c4b400000

Reported-by: syzbot+979ffc...@syzkaller.appspotmail.com
Fixes: 96e5da7c8424 ("memory: tegra: Introduce Tegra20 EMC driver")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection