WARNING in zap_class

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    babf09c3 Merge tag 'tag-chrome-platform-fixes-for-v5.1-rc2..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1509f28b200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9a31fb246de2a622
dashboard link: https://syzkaller.appspot.com/bug?extid=740dcc3824577fb40563
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+740dcc3824577fb40563@xxxxxxxxxxxxxxxxxxxxxxxxx

WARNING: CPU: 0 PID: 24046 at kernel/locking/lockdep.c:4548  
remove_class_from_lock_chain kernel/locking/lockdep.c:4528 [inline]
WARNING: CPU: 0 PID: 24046 at kernel/locking/lockdep.c:4548  
remove_class_from_lock_chains kernel/locking/lockdep.c:4568 [inline]
WARNING: CPU: 0 PID: 24046 at kernel/locking/lockdep.c:4548  
zap_class+0x741/0xe20 kernel/locking/lockdep.c:4607
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 24046 Comm: kworker/0:1 Not tainted 5.1.0-rc1+ #30
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events pwq_unbound_release_workfn
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 panic+0x2cb/0x65c kernel/panic.c:214
 __warn.cold+0x20/0x45 kernel/panic.c:571
 report_bug+0x263/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
RIP: 0010:remove_class_from_lock_chain kernel/locking/lockdep.c:4548  
[inline]
RIP: 0010:remove_class_from_lock_chains kernel/locking/lockdep.c:4568  
[inline]
RIP: 0010:zap_class+0x741/0xe20 kernel/locking/lockdep.c:4607
Code: 0f b6 14 38 4c 89 e0 83 e0 07 83 c0 01 38 d0 0f 8c 79 ff ff ff 84 d2  
0f 84 71 ff ff ff 4c 89 e7 e8 04 e8 51 00 e9 64 ff ff ff <0f> 0b e8 78 82  
d6 01 e9 4e fb ff ff 48 89 55 c0 4c 89 4d c8 e8 26
RSP: 0018:ffff88807a9e7c10 EFLAGS: 00010012
RAX: 0000000000010000 RBX: 11a523fb5c4fd01d RCX: ffffffff832ee40e
RDX: 00000000000035a5 RSI: ffffffff832ee45a RDI: 0000000000000006
RBP: ffff88807a9e7c68 R08: ffff88805a856280 R09: ffffffff8a08a408
R10: 0000000000960392 R11: 0000000003920adb R12: ffffffff89c19ec8
R13: 0000000000000000 R14: ffffffff89c19ec0 R15: dffffc0000000000
 __lockdep_free_key_range+0x64/0x120 kernel/locking/lockdep.c:4730
 lockdep_unregister_key+0x201/0x4c0 kernel/locking/lockdep.c:4926
 wq_unregister_lockdep kernel/workqueue.c:3455 [inline]
 pwq_unbound_release_workfn+0x233/0x2f0 kernel/workqueue.c:3675
 process_one_work+0x98e/0x1790 kernel/workqueue.c:2269
 worker_thread+0x98/0xe40 kernel/workqueue.c:2415
 kthread+0x357/0x430 kernel/kthread.c:253
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..


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