Bluetooth: hci_core: Avoid mixing up req_complete and req_complete_skb

In commit 44d27137 ("Bluetooth: Compress the size of struct
hci_ctrl") we squashed down the size of the structure by using a union
with the assumption that all users would use the flag to determine
whether we had a req_complete or a req_complete_skb.

Unfortunately we had a case in hci_req_cmd_complete() where we weren't
looking at the flag.  This can result in a situation where we might be
storing a hci_req_complete_skb_t in a hci_req_complete_t variable, or
vice versa.

During some testing I found at least one case where the function
hci_req_sync_complete() was called improperly because the kernel thought
that it didn't require an SKB.  Looking through the stack in kgdb I
found that it was called by hci_event_packet() and that
hci_event_packet() had both of its locals "req_complete" and
"req_complete_skb" pointing to the same place: both to
hci_req_sync_complete().

Let's make sure we always check the flag.

For more details on debugging done, see <http://crbug.com/588288>.

Fixes: 44d27137 ("Bluetooth: Compress the size of struct hci_ctrl")
Signed-off-by: NDouglas Anderson <dianders@chromium.org>
Acked-by: NJohan Hedberg <johan.hedberg@intel.com>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

net/bluetooth/hci_core.c

@@ -4112,8 +4112,10 @@ void hci_req_cmd_complete(struct hci_dev *hdev, u16 opcode, u8 status,
 			break;
 		}
 
-		*req_complete = bt_cb(skb)->hci.req_complete;
-		*req_complete_skb = bt_cb(skb)->hci.req_complete_skb;
+		if (bt_cb(skb)->hci.req_flags & HCI_REQ_SKB)
+			*req_complete_skb = bt_cb(skb)->hci.req_complete_skb;
+		else
+			*req_complete = bt_cb(skb)->hci.req_complete;
 		kfree_skb(skb);
 	}
 	spin_unlock_irqrestore(&hdev->cmd_q.lock, flags);