firewire: cdev: tcodes input validation

The behaviour of fw-transaction.c::fw_send_request is ill-defined for
any other tcodes than read/ write/ lock request tcodes.  Therefore
prevent requests with wrong tcodes from entering the transaction layer.

Maybe fw_send_request should check them itself, but I am not inclined to
change it and fw_fill_request from void-valued functions to ones which
return error codes and pass those up.  Besides, maybe fw_send_request is
going to support one more tcode than ioctl_send_request in the future
(TCODE_STREAM_DATA).
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/fw-cdev.c

@@ -398,6 +398,7 @@ static int ioctl_send_request(struct client *client, void *buffer)
 	struct fw_device *device = client->device;
 	struct fw_cdev_send_request *request = buffer;
 	struct response *response;
+	int ret;
 
 	/* What is the biggest size we'll accept, really? */
 	if (request->length > 4096)
@@ -414,8 +415,26 @@ static int ioctl_send_request(struct client *client, void *buffer)
 	if (request->data &&
 	    copy_from_user(response->response.data,
 			   u64_to_uptr(request->data), request->length)) {
-		kfree(response);
-		return -EFAULT;
+		ret = -EFAULT;
+		goto err;
+	}
+
+	switch (request->tcode) {
+	case TCODE_WRITE_QUADLET_REQUEST:
+	case TCODE_WRITE_BLOCK_REQUEST:
+	case TCODE_READ_QUADLET_REQUEST:
+	case TCODE_READ_BLOCK_REQUEST:
+	case TCODE_LOCK_MASK_SWAP:
+	case TCODE_LOCK_COMPARE_SWAP:
+	case TCODE_LOCK_FETCH_ADD:
+	case TCODE_LOCK_LITTLE_ADD:
+	case TCODE_LOCK_BOUNDED_ADD:
+	case TCODE_LOCK_WRAP_ADD:
+	case TCODE_LOCK_VENDOR_DEPENDENT:
+		break;
+	default:
+		ret = -EINVAL;
+		goto err;
 	}
 
 	response->resource.release = release_transaction;
@@ -434,6 +453,10 @@ static int ioctl_send_request(struct client *client, void *buffer)
 		return sizeof(request) + request->length;
 	else
 		return sizeof(request);
+ err:
+	kfree(response);
+
+	return ret;
 }
 
 struct address_handler {