WARNING: locking bug in l2cap_chan_del

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 458a534c Linux 4.14.197
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=14dc0f71900000
kernel config: https://syzkaller.appspot.com/x/.config?x=9f83b94e7eee9f66
dashboard link: https://syzkaller.appspot.com/bug?extid=b4f2ff10d615fa69f0eb
compiler: gcc (GCC) 10.1.0-syz 20200507

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b4f2ff...@syzkaller.appspotmail.com

DEBUG_LOCKS_WARN_ON(class_idx > MAX_LOCKDEP_KEYS)
------------[ cut here ]------------
WARNING: CPU: 0 PID: 18448 at kernel/locking/lockdep.c:3468 __lock_acquire.cold+0x7c0/0x97c kernel/locking/lockdep.c:3468
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 18448 Comm: syz-executor.3 Not tainted 4.14.197-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x1b2/0x283 lib/dump_stack.c:58
panic+0x1f9/0x42d kernel/panic.c:183
__warn.cold+0x20/0x4b kernel/panic.c:547
report_bug+0x208/0x249 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:177 [inline]
fixup_bug arch/x86/kernel/traps.c:172 [inline]
do_error_trap+0x195/0x2d0 arch/x86/kernel/traps.c:295
invalid_op+0x1b/0x40 arch/x86/entry/entry_64.S:964
RIP: 0010:__lock_acquire.cold+0x7c0/0x97c kernel/locking/lockdep.c:3468
RSP: 0018:ffff88809716f5a8 EFLAGS: 00010086
RAX: 0000000000000031 RBX: 0000000000000006 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffed1012e2deab
RBP: ffff888088b68f32 R08: 0000000000000031 R09: 0000000000000000
R10: 0000000000000001 R11: 0000006aea20cfc0 R12: ffff888088b68f28
R13: 0000000000000000 R14: 00000000b6d7a62f R15: ffffffff8a5a8c00
lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:176
spin_lock_bh include/linux/spinlock.h:322 [inline]
lock_sock_nested+0x39/0x100 net/core/sock.c:2788
l2cap_sock_teardown_cb+0x7b/0x400 net/bluetooth/l2cap_sock.c:1329
l2cap_chan_del+0xa0/0x800 net/bluetooth/l2cap_core.c:596
l2cap_conn_del+0x35f/0x670 net/bluetooth/l2cap_core.c:1726
l2cap_disconn_cfm net/bluetooth/l2cap_core.c:7435 [inline]
l2cap_disconn_cfm+0x6b/0x80 net/bluetooth/l2cap_core.c:7428
hci_disconn_cfm include/net/bluetooth/hci_core.h:1226 [inline]
hci_conn_hash_flush+0x114/0x220 net/bluetooth/hci_conn.c:1376
hci_dev_do_close+0x542/0xc50 net/bluetooth/hci_core.c:1620
hci_unregister_dev+0x170/0x7a0 net/bluetooth/hci_core.c:3191
vhci_release+0x70/0xe0 drivers/bluetooth/hci_vhci.c:354
__fput+0x25f/0x7a0 fs/file_table.c:210
task_work_run+0x11f/0x190 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0xa08/0x27f0 kernel/exit.c:865
do_group_exit+0x100/0x2e0 kernel/exit.c:962
get_signal+0x38d/0x1ca0 kernel/signal.c:2423
do_signal+0x7c/0x1550 arch/x86/kernel/signal.c:814
exit_to_usermode_loop+0x160/0x200 arch/x86/entry/common.c:160
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45d5b9
RSP: 002b:00007f75d6220cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000118d128 RCX: 000000000045d5b9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000118d128
RBP: 000000000118d120 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118d12c
R13: 00007ffc56c994ef R14: 00007f75d62219c0 R15: 000000000118d12c
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.