Re: WARNING: ODEBUG bug in netdev_freemem

From: syzbot
Date: Tue Jan 01 2019 - 23:10:46 EST

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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+979ffc89b87309b1b94b@xxxxxxxxxxxxxxxxxxxxxxxxx

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
Shutting down cpus with NMI
Kernel Offset: disabled
Rebooting in 86400 seconds..

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