WARNING: locking bug in l2cap_sock_teardown_cb

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c7150cd2 Linux 4.14.225
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15992f56d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=112b229d8a53892f
dashboard link: https://syzkaller.appspot.com/bug?extid=c6af4378d1b912effbf7

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+c6af43...@syzkaller.appspotmail.com

input: syz1 as /devices/virtual/input/input6
DEBUG_LOCKS_WARN_ON(class_idx > MAX_LOCKDEP_KEYS)
------------[ cut here ]------------
WARNING: CPU: 0 PID: 12136 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: 12136 Comm: syz-executor.4 Not tainted 4.14.225-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+0x1b2/0x281 lib/dump_stack.c:58
panic+0x1f9/0x42d kernel/panic.c:183
__warn.cold+0x20/0x44 kernel/panic.c:547
report_bug+0x208/0x250 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:ffff888048117598 EFLAGS: 00010086
RAX: 0000000000000031 RBX: 0000000000000007 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffed1009022ea9
RBP: ffff88809bd7ab32 R08: 0000000000000031 R09: 0000000000000000
R10: 0000000000000001 R11: 0000003471381bfd R12: ffff88809bd7ab28
R13: 0000000000000000 R14: 00000000dc490763 R15: ffffffff8beb5d40
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+0x93/0x650 net/bluetooth/l2cap_sock.c:1341
l2cap_chan_del+0xaf/0x950 net/bluetooth/l2cap_core.c:599
l2cap_conn_del+0x36e/0x690 net/bluetooth/l2cap_core.c:1729
l2cap_disconn_cfm net/bluetooth/l2cap_core.c:7441 [inline]
l2cap_disconn_cfm+0x7c/0xb0 net/bluetooth/l2cap_core.c:7434
hci_disconn_cfm include/net/bluetooth/hci_core.h:1226 [inline]
hci_conn_hash_flush+0x127/0x260 net/bluetooth/hci_conn.c:1393
hci_dev_do_close+0x535/0xca0 net/bluetooth/hci_core.c:1622
hci_unregister_dev+0x17f/0x8c0 net/bluetooth/hci_core.c:3193
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+0xa44/0x2850 kernel/exit.c:868
do_group_exit+0x100/0x2e0 kernel/exit.c:965
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: 0033:0x465f69
RSP: 002b:00007f1808a72218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000056c010 RCX: 0000000000465f69
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000056c010
RBP: 000000000056c008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c014
R13: 00007ffedb41bd8f R14: 00007f1808a72300 R15: 0000000000022000
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.