WARNING in default_device_exit_batch

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 08a45c59 Merge branch 'mptcp-part-two'
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1799f721e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=8d2cca7133bc3ccc
dashboard link: https://syzkaller.appspot.com/bug?extid=dfdfbdef099aa0f92df1
compiler: gcc (GCC) 9.0.0 20181231 (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+dfdfbd...@syzkaller.appspotmail.com

bond2 (unregistering): Released all slaves
------------[ cut here ]------------
WARNING: CPU: 1 PID: 7 at net/core/dev.c:8782 rollback_registered_many+0xcca/0x1030 net/core/dev.c:8782
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 7 Comm: kworker/u4:0 Not tainted 5.5.0-rc6-syzkaller #0
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+0x197/0x210 lib/dump_stack.c:118
panic+0x2e3/0x75c kernel/panic.c:221
__warn.cold+0x2f/0x3e kernel/panic.c:582
report_bug+0x289/0x300 lib/bug.c:195
fixup_bug arch/x86/kernel/traps.c:174 [inline]
fixup_bug arch/x86/kernel/traps.c:169 [inline]
do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:267
do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:286
invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
RIP: 0010:rollback_registered_many+0xcca/0x1030 net/core/dev.c:8782
Code: 6b 1a 00 00 48 c7 c6 40 b7 d6 88 48 c7 c7 20 b8 d6 88 c6 05 03 9f 52 04 01 e8 51 3b 20 fb 0f 0b e9 a1 fd ff ff e8 46 8b 4f fb <0f> 0b e9 76 fd ff ff e8 3a 8b 4f fb 0f 0b e9 af fa ff ff e8 2e 8b
RSP: 0018:ffffc90000cdf9c0 EFLAGS: 00010293
RAX: ffff8880a99a81c0 RBX: ffff888057e90000 RCX: ffffffff862571fe
RDX: 0000000000000000 RSI: ffffffff8625748a RDI: 0000000000000001
RBP: ffffc90000cdfae8 R08: ffff8880a99a81c0 R09: fffffbfff149c655
R10: fffffbfff149c654 R11: ffffffff8a4e32a7 R12: ffff8880946ee6c0
R13: dffffc0000000000 R14: 00000000a0105a01 R15: ffffc90000cdfac0
unregister_netdevice_many.part.0+0x1b/0x1f0 net/core/dev.c:9912
unregister_netdevice_many net/core/dev.c:9911 [inline]
default_device_exit_batch+0x360/0x420 net/core/dev.c:10385
ops_exit_list.isra.0+0x10c/0x160 net/core/net_namespace.c:175
cleanup_net+0x549/0xb10 net/core/net_namespace.c:589
process_one_work+0x9af/0x1740 kernel/workqueue.c:2264
worker_thread+0x98/0xe40 kernel/workqueue.c:2410
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

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