fix possible null-pointer dereference

Author: Youw

libusb/hid.c

@@ -1679,7 +1679,7 @@ int HID_API_EXPORT hid_send_feature_report(hid_device *dev, const unsigned char
 {
 	int res = -1;
 	int skipped_report_id = 0;
-	int report_number = data[0];
+	int report_number;
 
 	if (!data || !length) {
 		register_string_error(&dev->error, "Zero buffer/length");
@@ -1688,6 +1688,8 @@ int HID_API_EXPORT hid_send_feature_report(hid_device *dev, const unsigned char
 
 	register_libusb_error(&dev->error, LIBUSB_SUCCESS, NULL);
 
+	report_number = data[0]
+
 	if (report_number == 0x0) {
 		data++;
 		length--;
@@ -1718,7 +1720,7 @@ int HID_API_EXPORT hid_get_feature_report(hid_device *dev, unsigned char *data,
 {
 	int res = -1;
 	int skipped_report_id = 0;
-	int report_number = data[0];
+	int report_number;
 
 	if (!data || !length) {
 		register_string_error(&dev->error, "Zero buffer/length");
@@ -1727,6 +1729,8 @@ int HID_API_EXPORT hid_get_feature_report(hid_device *dev, unsigned char *data,
 
 	register_libusb_error(&dev->error, LIBUSB_SUCCESS, NULL);
 
+	report_number = data[0]
+
 	if (report_number == 0x0) {
 		/* Offset the return buffer by 1, so that the report ID
 		   will remain in byte 0. */
@@ -1757,7 +1761,7 @@ int HID_API_EXPORT hid_send_output_report(hid_device *dev, const unsigned char *
 {
 	int res = -1;
 	int skipped_report_id = 0;
-	int report_number = data[0];
+	int report_number;
 
 	if (!data || !length) {
 		register_string_error(&dev->error, "Zero buffer/length");
@@ -1766,6 +1770,8 @@ int HID_API_EXPORT hid_send_output_report(hid_device *dev, const unsigned char *
 
 	register_libusb_error(&dev->error, LIBUSB_SUCCESS, NULL);
 
+	report_number = data[0]
+
 	if (report_number == 0x0) {
 		data++;
 		length--;
@@ -1796,7 +1802,7 @@ int HID_API_EXPORT HID_API_CALL hid_get_input_report(hid_device *dev, unsigned c
 {
 	int res = -1;
 	int skipped_report_id = 0;
-	int report_number = data[0];
+	int report_number;
 
 	if (!data || !length) {
 		register_string_error(&dev->error, "Zero buffer/length");
@@ -1805,6 +1811,8 @@ int HID_API_EXPORT HID_API_CALL hid_get_input_report(hid_device *dev, unsigned c
 
 	register_libusb_error(&dev->error, LIBUSB_SUCCESS, NULL);
 
+	report_number = data[0];
+
 	if (report_number == 0x0) {
 		/* Offset the return buffer by 1, so that the report ID
 		   will remain in byte 0. */