Bluetooth: hci_event: validate skb length for unknown CC opcode

Bluetooth: hci_event: validate skb length for unknown CC opcode

In hci_cmd_complete_evt(), if the command complete event has an unknown
opcode, we assume the first byte of the remaining skb->data contains the
return status. However, parameter data has previously been pulled in
hci_event_func(), which may leave the skb empty. If so, using skb->data[0]
for the return status uses un-init memory.

The fix is to check skb->len before using skb->data.

Reported-by: syzbot+a9a4bedfca6aa9d7fa24@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=a9a4bedfca6aa9d7fa24
Tested-by: syzbot+a9a4bedfca6aa9d7fa24@syzkaller.appspotmail.com
Fixes: afcb3369f46ed ("Bluetooth: hci_event: Fix vendor (unknown) opcode status handling")
Signed-off-by: Raphael Pinsonneault-Thibeault <rpthibeault@gmail.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>