Bluetooth: hci_conn: Fix UAF in hci_enhanced_setup_sync

This checks if the ACL connection remains valid as it could be destroyed
while hci_enhanced_setup_sync is pending on cmd_sync leading to the
following trace:

BUG: KASAN: slab-use-after-free in hci_enhanced_setup_sync+0x91b/0xa60
Read of size 1 at addr ffff888002328ffd by task kworker/u5:2/37

CPU: 0 UID: 0 PID: 37 Comm: kworker/u5:2 Not tainted 6.11.0-rc6-01300-g810be445d8d6 #7099
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-2.fc40 04/01/2014
Workqueue: hci0 hci_cmd_sync_work
Call Trace:
 <TASK>
 dump_stack_lvl+0x5d/0x80
 ? hci_enhanced_setup_sync+0x91b/0xa60
 print_report+0x152/0x4c0
 ? hci_enhanced_setup_sync+0x91b/0xa60
 ? __virt_addr_valid+0x1fa/0x420
 ? hci_enhanced_setup_sync+0x91b/0xa60
 kasan_report+0xda/0x1b0
 ? hci_enhanced_setup_sync+0x91b/0xa60
 hci_enhanced_setup_sync+0x91b/0xa60
 ? __pfx_hci_enhanced_setup_sync+0x10/0x10
 ? __pfx___mutex_lock+0x10/0x10
 hci_cmd_sync_work+0x1c2/0x330
 process_one_work+0x7d9/0x1360
 ? __pfx_lock_acquire+0x10/0x10
 ? __pfx_process_one_work+0x10/0x10
 ? assign_work+0x167/0x240
 worker_thread+0x5b7/0xf60
 ? __kthread_parkme+0xac/0x1c0
 ? __pfx_worker_thread+0x10/0x10
 ? __pfx_worker_thread+0x10/0x10
 kthread+0x293/0x360
 ? __pfx_kthread+0x10/0x10
 ret_from_fork+0x2f/0x70
 ? __pfx_kthread+0x10/0x10
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Allocated by task 34:
 kasan_save_stack+0x30/0x50
 kasan_save_track+0x14/0x30
 __kasan_kmalloc+0x8f/0xa0
 __hci_conn_add+0x187/0x17d0
 hci_connect_sco+0x2e1/0xb90
 sco_sock_connect+0x2a2/0xb80
 __sys_connect+0x227/0x2a0
 __x64_sys_connect+0x6d/0xb0
 do_syscall_64+0x71/0x140
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 37:
 kasan_save_stack+0x30/0x50
 kasan_save_track+0x14/0x30
 kasan_save_free_info+0x3b/0x60
 __kasan_slab_free+0x101/0x160
 kfree+0xd0/0x250
 device_release+0x9a/0x210
 kobject_put+0x151/0x280
 hci_conn_del+0x448/0xbf0
 hci_abort_conn_sync+0x46f/0x980
 hci_cmd_sync_work+0x1c2/0x330
 process_one_work+0x7d9/0x1360
 worker_thread+0x5b7/0xf60
 kthread+0x293/0x360
 ret_from_fork+0x2f/0x70
 ret_from_fork_asm+0x1a/0x30

Cc: stable@vger.kernel.org
Fixes: e07a06b4 ("Bluetooth: Convert SCO configure_datapath to hci_sync")
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

net/bluetooth/hci_conn.c

@@ -289,6 +289,9 @@ static int hci_enhanced_setup_sync(struct hci_dev *hdev, void *data)
 
 	kfree(conn_handle);
 
+	if (!hci_conn_valid(hdev, conn))
+		return -ECANCELED;
+
 	bt_dev_dbg(hdev, "hcon %p", conn);
 
 	configure_datapath_sync(hdev, &conn->codec);