WARNING: locking bug in l2cap_sock_teardown_cb (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=163d966bf00000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=46991871b4264ba67ffe
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

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+469918...@syzkaller.appspotmail.com

------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(class_idx > MAX_LOCKDEP_KEYS)
WARNING: CPU: 0 PID: 2855 at kernel/locking/lockdep.c:3393 __lock_acquire+0x1221/0x3ff0 kernel/locking/lockdep.c:3393
IPVS: ftp: loaded support on port[0] = 21
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 2855 Comm: kworker/0:2 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events l2cap_chan_timeout
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
panic+0x26a/0x50e kernel/panic.c:186
__warn.cold+0x20/0x5a kernel/panic.c:541
report_bug+0x262/0x2b0 lib/bug.c:183
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x1d7/0x310 arch/x86/kernel/traps.c:296
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1038
RIP: 0010:__lock_acquire+0x1221/0x3ff0 kernel/locking/lockdep.c:3393
Code: d2 0f 85 2d 1f 00 00 44 8b 3d 5b ed eb 0b 45 85 ff 0f 85 78 ef ff ff 48 c7 c6 e0 43 6a 88 48 c7 c7 40 19 6a 88 e8 54 b3 a7 06 <0f> 0b e9 61 ef ff ff 8b 05 52 2d d9 0b 85 c0 0f 85 4e f9 ff ff 4c
RSP: 0018:ffff8880adf07930 EFLAGS: 00010082
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff814dff01 RDI: ffffed1015be0f18
RBP: ffff8880adef6e8a R08: 0000000000000000 R09: 000000000000287f
R10: 0000000000000006 R11: ffffffff8c66501b R12: 000000000004066f
R13: ffff8880adef6540 R14: ffff8880adef6e80 R15: 0000000000000000
lock_acquire+0x170/0x3c0 kernel/locking/lockdep.c:3908
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:168
spin_lock_bh include/linux/spinlock.h:334 [inline]
lock_sock_nested+0x3b/0x110 net/core/sock.c:2884
l2cap_sock_teardown_cb+0xa0/0x6d0 net/bluetooth/l2cap_sock.c:1348
l2cap_chan_del+0xbc/0xa50 net/bluetooth/l2cap_core.c:603
l2cap_chan_close+0x1b5/0x950 net/bluetooth/l2cap_core.c:761
l2cap_chan_timeout+0x17e/0x2f0 net/bluetooth/l2cap_core.c:430
process_one_work+0x864/0x1570 kernel/workqueue.c:2153
worker_thread+0x64c/0x1130 kernel/workqueue.c:2296
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
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.