CVE-2023-53673: Bluetooth: hci_event: call disconnect callback before deleting conn
In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: hci_event: call disconnect callback before deleting conn

In hci_cs_disconnect, we do hci_conn_del even if disconnection failed.

ISO, L2CAP and SCO connections refer to the hci_conn without
hci_conn_get, so disconn_cfm must be called so they can clean up their
conn, otherwise use-after-free occurs.

ISO:
==========================================================
iso_sock_connect:880: sk 00000000eabd6557
iso_connect_cis:356: 70:1a:b8:98:ff:a2 -> 28:3d:c2:4a:7e:da
...
iso_conn_add:140: hcon 000000001696f1fd conn 00000000b6251073
hci_dev_put:1487: hci0 orig refcnt 17
__iso_chan_add:214: conn 00000000b6251073
iso_sock_clear_timer:117: sock 00000000eabd6557 state 3
...
hci_rx_work:4085: hci0 Event packet
hci_event_packet:7601: hci0: event 0x0f
hci_cmd_status_evt:4346: hci0: opcode 0x0406
hci_cs_disconnect:2760: hci0: status 0x0c
hci_sent_cmd_data:3107: hci0 opcode 0x0406
hci_conn_del:1151: hci0 hcon 000000001696f1fd handle 2560
hci_conn_unlink:1102: hci0: hcon 000000001696f1fd
hci_conn_drop:1451: hcon 00000000d8521aaf orig refcnt 2
hci_chan_list_flush:2780: hcon 000000001696f1fd
hci_dev_put:1487: hci0 orig refcnt 21
hci_dev_put:1487: hci0 orig refcnt 20
hci_req_cmd_complete:3978: opcode 0x0406 status 0x0c
... <no iso_* activity on sk/conn> ...
iso_sock_sendmsg:1098: sock 00000000dea5e2e0, sk 00000000eabd6557
BUG: kernel NULL pointer dereference, address: 0000000000000668
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP PTI
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc38 04/01/2014
RIP: 0010:iso_sock_sendmsg (net/bluetooth/iso.c:1112) bluetooth
==========================================================

L2CAP:
==================================================================
hci_cmd_status_evt:4359: hci0: opcode 0x0406
hci_cs_disconnect:2760: hci0: status 0x0c
hci_sent_cmd_data:3085: hci0 opcode 0x0406
hci_conn_del:1151: hci0 hcon ffff88800c999000 handle 3585
hci_conn_unlink:1102: hci0: hcon ffff88800c999000
hci_chan_list_flush:2780: hcon ffff88800c999000
hci_chan_del:2761: hci0 hcon ffff88800c999000 chan ffff888018ddd280
...
BUG: KASAN: slab-use-after-free in hci_send_acl+0x2d/0x540 [bluetooth]
Read of size 8 at addr ffff888018ddd298 by task bluetoothd/1175

CPU: 0 PID: 1175 Comm: bluetoothd Tainted: G            E      6.4.0-rc4+ #2
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-1.fc38 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x5b/0x90
 print_report+0xcf/0x670
 ? __virt_addr_valid+0xf8/0x180
 ? hci_send_acl+0x2d/0x540 [bluetooth]
 kasan_report+0xa8/0xe0
 ? hci_send_acl+0x2d/0x540 [bluetooth]
 hci_send_acl+0x2d/0x540 [bluetooth]
 ? __pfx___lock_acquire+0x10/0x10
 l2cap_chan_send+0x1fd/0x1300 [bluetooth]
 ? l2cap_sock_sendmsg+0xf2/0x170 [bluetooth]
 ? __pfx_l2cap_chan_send+0x10/0x10 [bluetooth]
 ? lock_release+0x1d5/0x3c0
 ? mark_held_locks+0x1a/0x90
 l2cap_sock_sendmsg+0x100/0x170 [bluetooth]
 sock_write_iter+0x275/0x280
 ? __pfx_sock_write_iter+0x10/0x10
 ? __pfx___lock_acquire+0x10/0x10
 do_iter_readv_writev+0x176/0x220
 ? __pfx_do_iter_readv_writev+0x10/0x10
 ? find_held_lock+0x83/0xa0
 ? selinux_file_permission+0x13e/0x210
 do_iter_write+0xda/0x340
 vfs_writev+0x1b4/0x400
 ? __pfx_vfs_writev+0x10/0x10
 ? __seccomp_filter+0x112/0x750
 ? populate_seccomp_data+0x182/0x220
 ? __fget_light+0xdf/0x100
 ? do_writev+0x19d/0x210
 do_writev+0x19d/0x210
 ? __pfx_do_writev+0x10/0x10
 ? mark_held_locks+0x1a/0x90
 do_syscall_64+0x60/0x90
 ? lockdep_hardirqs_on_prepare+0x149/0x210
 ? do_syscall_64+0x6c/0x90
 ? lockdep_hardirqs_on_prepare+0x149/0x210
 entry_SYSCALL_64_after_hwframe+0x72/0xdc
RIP: 0033:0x7ff45cb23e64
Code: 15 d1 1f 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b8 0f 1f 00 f3 0f 1e fa 80 3d 9d a7 0d 00 00 74 13 b8 14 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 48 83 ec 28 89 54 24 1c 48 89
RSP: 002b:00007fff21ae09b8 EFLAGS: 00000202 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 
---truncated---
CVSS v3.1: 7.8