------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: lib/refcount.c:28 at refcount_warn_saturate+0xf4/0x130 lib/refcount.c:28, CPU#2: syz-executor/2424
Modules linked in:
CPU: 2 UID: 0 PID: 2424 Comm: syz-executor Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:refcount_warn_saturate+0xf4/0x130 lib/refcount.c:28
Code: cc e8 50 4e 0f fd 48 8d 3d 39 46 e8 0b 67 48 0f b9 3a e8 3f 4e 0f fd 5b 5d e9 58 69 93 06 e8 33 4e 0f fd 48 8d 3d 2c 46 e8 0b <67> 48 0f b9 3a e8 22 4e 0f fd 5b 5d c3 cc cc cc cc e8 16 4e 0f fd
RSP: 0018:ffffc90006b4f6d8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff888027ed8078 RCX: ffffffff84f962bb
RDX: ffff888044dd4a80 RSI: ffffffff84f9634d RDI: ffffffff90e1a980
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000004
R10: 0000000000000003 R11: 0000000000000001 R12: ffff88804d785800
R13: ffff888027ed8078 R14: ffffffff86358ac0 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8880d6587000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f133c2dea90 CR3: 00000000375bc000 CR4: 0000000000352ef0
DR0: 0000000000000101 DR1: 0000000000000007 DR2: 000000000000000f
DR3: 0000000000000006 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_sub_and_test include/linux/refcount.h:400 [inline]
 __refcount_dec_and_test include/linux/refcount.h:432 [inline]
 refcount_dec_and_test include/linux/refcount.h:450 [inline]
 kref_put include/linux/kref.h:64 [inline]
 klist_dec_and_del lib/klist.c:206 [inline]
 klist_put+0x18a/0x1d0 lib/klist.c:217
 klist_del lib/klist.c:230 [inline]
 klist_remove+0x14c/0x2e0 lib/klist.c:249
 device_move+0x12d/0x1140 drivers/base/core.c:4632
 hci_conn_del_sysfs+0x86/0x1a0 net/bluetooth/hci_sysfs.c:75
 hci_conn_cleanup net/bluetooth/hci_conn.c:173 [inline]
 hci_conn_del+0x506/0x1180 net/bluetooth/hci_conn.c:1309
 hci_conn_hash_flush+0x186/0x280 net/bluetooth/hci_conn.c:2737
 hci_dev_close_sync+0x5cf/0x13c0 net/bluetooth/hci_sync.c:5383
 hci_dev_do_close+0x2e/0xb0 net/bluetooth/hci_core.c:502
 hci_unregister_dev+0x227/0x670 net/bluetooth/hci_core.c:2679
 vhci_release+0x17d/0x230 drivers/bluetooth/hci_vhci.c:690
 __fput+0x3ff/0xb50 fs/file_table.c:510
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x951/0x2af0 kernel/exit.c:976
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1119
 get_signal+0x20ff/0x2210 kernel/signal.c:3038
 arch_do_signal_or_restart+0x91/0x7e0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x98/0x670 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x666/0x870 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fad3415d68e
Code: Unable to access opcode bytes at 0x7fad3415d664.
RSP: 002b:00007ffee122b268 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: fffffffffffffe00 RBX: 0000555588dd9500 RCX: 00007fad3415d68e
RDX: 0000000000000030 RSI: 00007ffee122b360 RDI: 00000000000000f9
RBP: 00007ffee122b30c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000258
R13: 00000000000927c0 R14: 00000000000d8673 R15: 00007ffee122b360
 </TASK>
----------------
Code disassembly (best guess):
   0:	cc                   	int3
   1:	e8 50 4e 0f fd       	call   0xfd0f4e56
   6:	48 8d 3d 39 46 e8 0b 	lea    0xbe84639(%rip),%rdi        # 0xbe84646
   d:	67 48 0f b9 3a       	ud1    (%edx),%rdi
  12:	e8 3f 4e 0f fd       	call   0xfd0f4e56
  17:	5b                   	pop    %rbx
  18:	5d                   	pop    %rbp
  19:	e9 58 69 93 06       	jmp    0x6936976
  1e:	e8 33 4e 0f fd       	call   0xfd0f4e56
  23:	48 8d 3d 2c 46 e8 0b 	lea    0xbe8462c(%rip),%rdi        # 0xbe84656
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	e8 22 4e 0f fd       	call   0xfd0f4e56
  34:	5b                   	pop    %rbx
  35:	5d                   	pop    %rbp
  36:	c3                   	ret
  37:	cc                   	int3
  38:	cc                   	int3
  39:	cc                   	int3
  3a:	cc                   	int3
  3b:	e8 16 4e 0f fd       	call   0xfd0f4e56