Bluetooth: btusb: validate Realtek vendor event length

[ Upstream commit df541cd ]

btusb_recv_event_realtek() reads the event code at data[0] and the Realtek
subevent code at data[2] before deciding whether to consume a vendor event
as a coredump.

For example, the two-byte event ff 00 contains a complete vendor-event
header declaring zero parameters. The old classifier still reads a
nonexistent third byte and can misclassify the event as a coredump if the
adjacent byte is 0x34.

Require the HCI event header and first parameter to be present before
inspecting the Realtek subevent code. Short events continue through the
normal HCI receive path, which owns their protocol validation.

Fixes: 044014c ("Bluetooth: btrtl: Add Realtek devcoredump support")
Signed-off-by: Pengpeng Hou <pengpeng@iscas.ac.cn>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: neosys007

drivers/bluetooth/btusb.c

@@ -2671,7 +2671,9 @@ static int btusb_setup_realtek(struct hci_dev *hdev)
 
 static int btusb_recv_event_realtek(struct hci_dev *hdev, struct sk_buff *skb)
 {
-	if (skb->data[0] == HCI_VENDOR_PKT && skb->data[2] == RTK_SUB_EVENT_CODE_COREDUMP) {
+	if (skb->len >= HCI_EVENT_HDR_SIZE + 1 &&
+	    skb->data[0] == HCI_VENDOR_PKT &&
+	    skb->data[2] == RTK_SUB_EVENT_CODE_COREDUMP) {
 		struct rtk_dev_coredump_hdr hdr = {
 			.code = RTK_DEVCOREDUMP_CODE_MEMDUMP,
 		};