WARNING in lockdep_unregister_key (2)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    6d0a5984 Merge branch 'x86-urgent-for-linus' of git://git...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=178c986b200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=4fb64439e07a1ec0
dashboard link: https://syzkaller.appspot.com/bug?extid=800069ac21123326861a
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+800069ac21123326861a@xxxxxxxxxxxxxxxxxxxxxxxxx

WARNING: CPU: 0 PID: 7126 at kernel/locking/lockdep.c:4920  
lockdep_unregister_key+0x3bf/0x510 kernel/locking/lockdep.c:4906
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 7126 Comm: kworker/0:1 Not tainted 5.1.0-rc4+ #65
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:lockdep_unregister_key+0x3bf/0x510 kernel/locking/lockdep.c:4920
Code: 00 00 00 00 48 8b 45 d0 65 48 33 04 25 28 00 00 00 0f 85 48 01 00 00  
48 83 c4 70 5b 41 5c 41 5d 41 5e 41 5f 5d c3 0f 0b eb c7 <0f> 0b e9 e9 fe  
ff ff 0f 0b 0f 0b 48 c7 c2 e0 97 92 88 89 43 c0 48
RSP: 0018:ffff888059cbfc50 EFLAGS: 00010046
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8156dfd8
RDX: 1ffffffff1467ac7 RSI: 0000000000000004 RDI: ffffffff8a33d638
RBP: ffff888059cbfce8 R08: 0000000000002010 R09: ffffed100b397f91
R10: ffffed100b397f90 R11: 0000000000000003 R12: ffff88808d893dd8
R13: 1ffff1100b397f8c R14: ffffffff8a0b9788 R15: dffffc0000000000
 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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