Bluetooth: Make use of skb_pull to parse L2CAP signaling PDUs

This uses skb_pull when parsing signalling PDUs so skb->data for
pointing to the current PDU and skb->len as the remaining bytes to be
processed.
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/l2cap_core.c

@@ -5835,9 +5835,7 @@ static inline void l2cap_sig_channel(struct l2cap_conn *conn,
 				     struct sk_buff *skb)
 {
 	struct hci_conn *hcon = conn->hcon;
-	u8 *data = skb->data;
-	int len = skb->len;
-	struct l2cap_cmd_hdr cmd;
+	struct l2cap_cmd_hdr *cmd;
 	int err;
 
 	l2cap_raw_recv(conn, skb);
@@ -5845,35 +5843,34 @@ static inline void l2cap_sig_channel(struct l2cap_conn *conn,
 	if (hcon->type != ACL_LINK)
 		goto drop;
 
-	while (len >= L2CAP_CMD_HDR_SIZE) {
-		u16 cmd_len;
-		memcpy(&cmd, data, L2CAP_CMD_HDR_SIZE);
-		data += L2CAP_CMD_HDR_SIZE;
-		len  -= L2CAP_CMD_HDR_SIZE;
+	while (skb->len >= L2CAP_CMD_HDR_SIZE) {
+		u16 len;
+
+		cmd = (void *) skb->data;
+		skb_pull(skb, L2CAP_CMD_HDR_SIZE);
 
-		cmd_len = le16_to_cpu(cmd.len);
+		len = le16_to_cpu(cmd->len);
 
-		BT_DBG("code 0x%2.2x len %d id 0x%2.2x", cmd.code, cmd_len,
-		       cmd.ident);
+		BT_DBG("code 0x%2.2x len %d id 0x%2.2x", cmd->code, len,
+		       cmd->ident);
 
-		if (cmd_len > len || !cmd.ident) {
+		if (len > skb->len || !cmd->ident) {
 			BT_DBG("corrupted command");
 			break;
 		}
 
-		err = l2cap_bredr_sig_cmd(conn, &cmd, cmd_len, data);
+		err = l2cap_bredr_sig_cmd(conn, cmd, len, skb->data);
 		if (err) {
 			struct l2cap_cmd_rej_unk rej;
 
 			BT_ERR("Wrong link type (%d)", err);
 
 			rej.reason = cpu_to_le16(L2CAP_REJ_NOT_UNDERSTOOD);
-			l2cap_send_cmd(conn, cmd.ident, L2CAP_COMMAND_REJ,
+			l2cap_send_cmd(conn, cmd->ident, L2CAP_COMMAND_REJ,
 				       sizeof(rej), &rej);
 		}
 
-		data += cmd_len;
-		len  -= cmd_len;
+		skb_pull(skb, len);
 	}
 
 drop: