------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 18541 at lib/refcount.c:28 refcount_warn_saturate+0x11a/0x1d0 lib/refcount.c:28
Modules linked in:
CPU: 0 UID: 0 PID: 18541 Comm: syz.2.3608 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:refcount_warn_saturate+0x11a/0x1d0 lib/refcount.c:28
Code: 40 b7 e2 8b e8 47 f0 ba fc 90 0f 0b 90 90 eb d7 e8 db 54 f7 fc c6 05 e3 2d c5 0a 01 90 48 c7 c7 a0 b7 e2 8b e8 27 f0 ba fc 90 <0f> 0b 90 90 eb b7 e8 bb 54 f7 fc c6 05 c0 2d c5 0a 01 90 48 c7 c7
RSP: 0018:ffffc9000428f8d8 EFLAGS: 00010246
RAX: 528db4a972320200 RBX: 0000000000000003 RCX: ffff8880791d1e00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: 0000000000000000 R08: ffffc9000428f607 R09: 1ffff92000851ec0
R10: dffffc0000000000 R11: fffff52000851ec1 R12: ffff8880328dc400
R13: ffff8881453b0c60 R14: ffff8881453b0c78 R15: dffffc0000000000
FS:  00007f1c5936a6c0(0000) GS:ffff888125c15000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffc81b69fc0 CR3: 000000003f862000 CR4: 00000000003526f0
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+0x3c7/0x3d0 lib/klist.c:206
 klist_put lib/klist.c:217 [inline]
 klist_del lib/klist.c:230 [inline]
 klist_remove+0x1bd/0x340 lib/klist.c:249
 device_move+0x193/0x700 drivers/base/core.c:4615
 hci_conn_del_sysfs+0xb8/0x170 net/bluetooth/hci_sysfs.c:75
 hci_conn_cleanup net/bluetooth/hci_conn.c:173 [inline]
 hci_conn_del+0xc33/0x11b0 net/bluetooth/hci_conn.c:1211
 hci_conn_hash_flush+0x191/0x230 net/bluetooth/hci_conn.c:2600
 hci_dev_close_sync+0xaef/0x1330 net/bluetooth/hci_sync.c:5294
 hci_dev_do_close net/bluetooth/hci_core.c:501 [inline]
 hci_dev_close+0x108/0x200 net/bluetooth/hci_core.c:526
 sock_do_ioctl+0xdc/0x300 net/socket.c:1238
 sock_ioctl+0x576/0x790 net/socket.c:1359
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1c5858eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1c5936a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f1c587d5fa0 RCX: 00007f1c5858eba9
RDX: 0000000000000000 RSI: 00000000400448ca RDI: 0000000000000005
RBP: 00007f1c58611e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1c587d6038 R14: 00007f1c587d5fa0 R15: 00007ffc9d7a3fe8
 </TASK>