can: kvaser_usb: validate command format before parsing in hydra receive path

index efbb7bed34c9..eddd207ee8da 100644
@@ -536,6 +536,24 @@ static size_t kvaser_usb_hydra_cmd_size(struct kvaser_cmd *cmd)
 	return ret;
 }
 
+/* -EAGAIN means incomplete; -EINVAL rejects zero to ensure progress. */
+static int kvaser_usb_hydra_cmd_size_rx(struct kvaser_cmd *cmd,
+					size_t remaining, size_t *cmd_len)
+{
+	if (remaining < sizeof(cmd->header.cmd_no))
+		return -EAGAIN;
+
+	if (cmd->header.cmd_no == CMD_EXTENDED &&
+	    remaining < offsetof(struct kvaser_cmd_ext, cmd_no_ext))
+		return -EAGAIN;
+
+	*cmd_len = kvaser_usb_hydra_cmd_size(cmd);
+	if (!*cmd_len)
+		return -EINVAL;
+
+	return 0;
+}
+
 static struct kvaser_usb_net_priv *
 kvaser_usb_hydra_net_priv_from_cmd(const struct kvaser_usb *dev,
 				   const struct kvaser_cmd *cmd)

@@ -675,8 +693,10 @@ static int kvaser_usb_hydra_wait_cmd(const struct kvaser_usb *dev, u8 cmd_no,
 			size_t cmd_len;
 
 			tmp_cmd = buf + pos;
-			cmd_len = kvaser_usb_hydra_cmd_size(tmp_cmd);
-			if (pos + cmd_len > actual_len) {
+			err = kvaser_usb_hydra_cmd_size_rx(tmp_cmd,
+							   actual_len - pos,
+							   &cmd_len);
+			if (err || pos + cmd_len > actual_len) {
 				dev_err_ratelimited(&dev->intf->dev,
 						    "Format error\n");
 				break;

@@ -2110,6 +2130,7 @@ static void kvaser_usb_hydra_read_bulk_callback(struct kvaser_usb *dev,
 {
 	unsigned long irq_flags;
 	struct kvaser_cmd *cmd;
+	int err;
 	int pos = 0;
 	size_t cmd_len;
 	struct kvaser_usb_dev_card_data_hydra *card_data =

@@ -2120,24 +2141,53 @@ static void kvaser_usb_hydra_read_bulk_callback(struct kvaser_usb *dev,
 	spin_lock_irqsave(usb_rx_leftover_lock, irq_flags);
 	usb_rx_leftover_len = card_data->usb_rx_leftover_len;
 	if (usb_rx_leftover_len) {
+		const size_t cmd_size_field_end =
+			offsetof(struct kvaser_cmd_ext, cmd_no_ext);
 		int remaining_bytes;
 
 		cmd = (struct kvaser_cmd *)card_data->usb_rx_leftover;
 
-		cmd_len = kvaser_usb_hydra_cmd_size(cmd);
+		if (cmd->header.cmd_no == CMD_EXTENDED &&
+		    usb_rx_leftover_len < cmd_size_field_end) {
+			remaining_bytes = min_t(int, len,
+						cmd_size_field_end -
+						usb_rx_leftover_len);
 
-		remaining_bytes = min_t(unsigned int, len,
+			memcpy(card_data->usb_rx_leftover + usb_rx_leftover_len,
+			       buf, remaining_bytes);
+			usb_rx_leftover_len += remaining_bytes;
+			card_data->usb_rx_leftover_len = usb_rx_leftover_len;
+			pos += remaining_bytes;
+
+			if (usb_rx_leftover_len < cmd_size_field_end) {
+				spin_unlock_irqrestore(usb_rx_leftover_lock,
+						       irq_flags);
+				return;
+			}
+		}
+
+		err = kvaser_usb_hydra_cmd_size_rx(cmd, usb_rx_leftover_len,
+						   &cmd_len);
+		if (err || cmd_len < usb_rx_leftover_len) {
+			dev_err(&dev->intf->dev, "Format error\n");
+			card_data->usb_rx_leftover_len = 0;
+			spin_unlock_irqrestore(usb_rx_leftover_lock, irq_flags);
+			return;
+		}
+
+		remaining_bytes = min_t(unsigned int, len - pos,
 					cmd_len - usb_rx_leftover_len);
 		/* Make sure we do not overflow usb_rx_leftover */
 		if (remaining_bytes + usb_rx_leftover_len >
 						KVASER_USB_HYDRA_MAX_CMD_LEN) {
 			dev_err(&dev->intf->dev, "Format error\n");
+			card_data->usb_rx_leftover_len = 0;
 			spin_unlock_irqrestore(usb_rx_leftover_lock, irq_flags);
 			return;
 		}
 
-		memcpy(card_data->usb_rx_leftover + usb_rx_leftover_len, buf,
-		       remaining_bytes);
+		memcpy(card_data->usb_rx_leftover + usb_rx_leftover_len,
+		       buf + pos, remaining_bytes);
 		pos += remaining_bytes;
 
 		if (remaining_bytes + usb_rx_leftover_len == cmd_len) {

@@ -2154,9 +2204,13 @@ static void kvaser_usb_hydra_read_bulk_callback(struct kvaser_usb *dev,
 	while (pos < len) {
 		cmd = buf + pos;
 
-		cmd_len = kvaser_usb_hydra_cmd_size(cmd);
+		err = kvaser_usb_hydra_cmd_size_rx(cmd, len - pos, &cmd_len);
+		if (err && err != -EAGAIN) {
+			dev_err(&dev->intf->dev, "Format error\n");
+			return;
+		}
 
-		if (pos + cmd_len > len) {
+		if (err == -EAGAIN || pos + cmd_len > len) {
 			/* We got first part of a command */
 			int leftover_bytes;