------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 2 PID: 22292 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 2 UID: 0 PID: 22292 Comm: syz.2.4870 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Code: ff 89 de e8 a8 1f 18 fd 84 db 0f 85 66 ff ff ff e8 bb 24 18 fd c6 05 5f dd c5 0b 01 90 48 c7 c7 80 c1 ef 8b e8 07 58 d6 fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 98 24 18 fd 0f b6 1d 3a dd c5 0b 31
RSP: 0018:ffffc9000d527718 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817b1cd8
RDX: ffff888049fb0000 RSI: ffffffff817b1ce5 RDI: 0000000000000001
RBP: ffff8880550a3478 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff8880552f3800
R13: ffff8880550a3478 R14: ffffffff85dae590 R15: ffffffff90655960
FS:  0000000000000000(0000) GS:ffff8880d6c05000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007faab1664f98 CR3: 000000000e182000 CR4: 0000000000352ef0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000083
DR3: ffffffffefffff15 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+0x11b/0x1b0 lib/klist.c:217
 klist_del lib/klist.c:230 [inline]
 klist_remove+0x13f/0x2e0 lib/klist.c:249
 device_move+0x12d/0x10d0 drivers/base/core.c:4615
 hci_conn_del_sysfs+0x81/0x180 net/bluetooth/hci_sysfs.c:75
 hci_conn_cleanup net/bluetooth/hci_conn.c:173 [inline]
 hci_conn_del+0x657/0x1180 net/bluetooth/hci_conn.c:1222
 hci_conn_hash_flush+0x186/0x260 net/bluetooth/hci_conn.c:2615
 hci_dev_close_sync+0x602/0x11d0 net/bluetooth/hci_sync.c:5308
 hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:501
 hci_unregister_dev+0x227/0x640 net/bluetooth/hci_core.c:2715
 vhci_release+0x17d/0x230 drivers/bluetooth/hci_vhci.c:690
 __fput+0x402/0xb70 fs/file_table.c:468
 task_work_run+0x150/0x240 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x86f/0x2bf0 kernel/exit.c:966
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1107
 get_signal+0x2671/0x26d0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x8f/0x7c0 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x85/0x130 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x426/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7faab078f749
Code: Unable to access opcode bytes at 0x7faab078f71f.
RSP: 002b:00007faab1665038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: 0000000000000001 RBX: 00007faab09e5fa0 RCX: 00007faab078f749
RDX: 0000000000000002 RSI: 00002000000017c0 RDI: 0000000000000007
RBP: 00007faab0813f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007faab09e6038 R14: 00007faab09e5fa0 R15: 00007ffd8c911c98
 </TASK>