print_req_error: I/O error, dev loop1, sector 0
INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
CPU: 1 PID: 4642 Comm: kworker/1:3 Not tainted 4.14.212-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:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 register_lock_class+0x32b/0x1320 kernel/locking/lockdep.c:768
 __lock_acquire+0x167/0x3f20 kernel/locking/lockdep.c:3378
 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_chan_close+0x103/0x870 net/bluetooth/l2cap_core.c:757
 l2cap_chan_timeout+0x143/0x2a0 net/bluetooth/l2cap_core.c:430
 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
BUG: unable to handle kernel NULL pointer dereference at           (null)
IP:           (null)
PGD a9045067 P4D a9045067 PUD a30ac067 PMD 0 
Oops: 0010 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 4642 Comm: kworker/1:3 Not tainted 4.14.212-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events l2cap_chan_timeout
task: ffff8880b48dc340 task.stack: ffff8880b4f80000
RIP: 0010:          (null)
RSP: 0018:ffff8880b4f87c08 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: 000000000000006f RCX: 1ffffffff1279f60
RDX: 1ffff11016645219 RSI: ffffffff8788bdc0 RDI: ffff8880b3228cc0
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: ffff8880b48dc340 R12: ffff8880a8f8e040
R13: ffff8880b3228cc0 R14: ffff88809fb5b1c0 R15: ffff8880a8f8e040
FS:  0000000000000000(0000) GS:ffff8880ba500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000009df26000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 l2cap_sock_teardown_cb+0x483/0x650 net/bluetooth/l2cap_sock.c:1366
 l2cap_chan_del+0xaf/0x950 net/bluetooth/l2cap_core.c:599
 l2cap_chan_close+0x103/0x870 net/bluetooth/l2cap_core.c:757
 l2cap_chan_timeout+0x143/0x2a0 net/bluetooth/l2cap_core.c:430
 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Code:  Bad RIP value.
RIP:           (null) RSP: ffff8880b4f87c08
CR2: 0000000000000000
---[ end trace 30bbfb98f49df7c3 ]---