Windows: WinUSB: Allow caching config descriptors to fail

Certain buggy devices may not provide all the advertised configuration
descriptors. Prior to this commit, failure to cache any one of the
descriptors would result in all of the descriptors being freed and the
device being inaccessible. Work around this by continuing on if fetching
a configuration descriptor fails. The device may still be usable if the
descriptor for the current configuration was successfully retrieved.

Closes #390

Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>

2 files changed, 32 insertions, 43 deletions

diff --git a/libusb/os/windows_winusb.c b/libusb/os/windows_winusb.c
index 1783700..2c4a81e 100644
--- a/libusb/os/windows_winusb.c
+++ b/libusb/os/windows_winusb.c
@@ -682,12 +682,11 @@ static void winusb_exit(struct libusb_context *ctx)
 /*
  * fetch and cache all the config descriptors through I/O
  */
-static int cache_config_descriptors(struct libusb_device *dev, HANDLE hub_handle)
+static void cache_config_descriptors(struct libusb_device *dev, HANDLE hub_handle)
 {
-	DWORD size, ret_size;
 	struct libusb_context *ctx = DEVICE_CTX(dev);
 	struct winusb_device_priv *priv = _device_priv(dev);
-	int r;
+	DWORD size, ret_size;
 	uint8_t i;
 
 	USB_CONFIGURATION_DESCRIPTOR_SHORT cd_buf_short; // dummy request
@@ -695,18 +694,18 @@ static int cache_config_descriptors(struct libusb_device *dev, HANDLE hub_handle
 	PUSB_CONFIGURATION_DESCRIPTOR cd_data;
 
 	if (dev->num_configurations == 0)
-		return LIBUSB_ERROR_INVALID_PARAM;
+		return;
 
 	priv->config_descriptor = calloc(dev->num_configurations, sizeof(PUSB_CONFIGURATION_DESCRIPTOR));
-	if (priv->config_descriptor == NULL)
-		return LIBUSB_ERROR_NO_MEM;
+	if (priv->config_descriptor == NULL) {
+		usbi_err(ctx, "could not allocate configuration descriptor array for '%s'", priv->dev_id);
+		return;
+	}
 
-	for (i = 0, r = LIBUSB_SUCCESS; ; i++) {
-		// safe loop: release all dynamic resources
+	for (i = 0; i <= dev->num_configurations; i++) {
 		safe_free(cd_buf_actual);
 
-		// safe loop: end of loop condition
-		if ((i >= dev->num_configurations) || (r != LIBUSB_SUCCESS))
+		if (i == dev->num_configurations)
 			break;
 
 		size = sizeof(cd_buf_short);
@@ -724,20 +723,20 @@ static int cache_config_descriptors(struct libusb_device *dev, HANDLE hub_handle
 		// coverity[tainted_data_argument]
 		if (!DeviceIoControl(hub_handle, IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION, &cd_buf_short, size,
 			&cd_buf_short, size, &ret_size, NULL)) {
-			usbi_info(ctx, "could not access configuration descriptor (dummy) for '%s': %s", priv->dev_id, windows_error_str(0));
-			LOOP_BREAK(LIBUSB_ERROR_IO);
+			usbi_info(ctx, "could not access configuration descriptor %u (dummy) for '%s': %s", i, priv->dev_id, windows_error_str(0));
+			continue;
 		}
 
 		if ((ret_size != size) || (cd_buf_short.desc.wTotalLength < sizeof(USB_CONFIGURATION_DESCRIPTOR))) {
-			usbi_info(ctx, "unexpected configuration descriptor size (dummy) for '%s'", priv->dev_id);
-			LOOP_BREAK(LIBUSB_ERROR_IO);
+			usbi_info(ctx, "unexpected configuration descriptor %u size (dummy) for '%s'", i, priv->dev_id);
+			continue;
 		}
 
 		size = sizeof(USB_DESCRIPTOR_REQUEST) + cd_buf_short.desc.wTotalLength;
 		cd_buf_actual = malloc(size);
 		if (cd_buf_actual == NULL) {
-			usbi_err(ctx, "could not allocate configuration descriptor buffer for '%s'", priv->dev_id);
-			LOOP_BREAK(LIBUSB_ERROR_NO_MEM);
+			usbi_err(ctx, "could not allocate configuration descriptor %u buffer for '%s'", i, priv->dev_id);
+			continue;
 		}
 
 		// Actual call
@@ -750,42 +749,33 @@ static int cache_config_descriptors(struct libusb_device *dev, HANDLE hub_handle
 
 		if (!DeviceIoControl(hub_handle, IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION, cd_buf_actual, size,
 			cd_buf_actual, size, &ret_size, NULL)) {
-			usbi_err(ctx, "could not access configuration descriptor (actual) for '%s': %s", priv->dev_id, windows_error_str(0));
-			LOOP_BREAK(LIBUSB_ERROR_IO);
+			usbi_err(ctx, "could not access configuration descriptor %u (actual) for '%s': %s", i, priv->dev_id, windows_error_str(0));
+			continue;
 		}
 
 		cd_data = (PUSB_CONFIGURATION_DESCRIPTOR)((UCHAR *)cd_buf_actual + sizeof(USB_DESCRIPTOR_REQUEST));
 
 		if ((size != ret_size) || (cd_data->wTotalLength != cd_buf_short.desc.wTotalLength)) {
-			usbi_err(ctx, "unexpected configuration descriptor size (actual) for '%s'", priv->dev_id);
-			LOOP_BREAK(LIBUSB_ERROR_IO);
+			usbi_err(ctx, "unexpected configuration descriptor %u size (actual) for '%s'", i, priv->dev_id);
+			continue;
 		}
 
 		if (cd_data->bDescriptorType != LIBUSB_DT_CONFIG) {
-			usbi_err(ctx, "not a configuration descriptor for '%s'", priv->dev_id);
-			LOOP_BREAK(LIBUSB_ERROR_IO);
+			usbi_err(ctx, "descriptor %u not a configuration descriptor for '%s'", i, priv->dev_id);
+			continue;
 		}
 
-		usbi_dbg("cached config descriptor %d (bConfigurationValue=%u, %u bytes)",
+		usbi_dbg("cached config descriptor %u (bConfigurationValue=%u, %u bytes)",
 			i, cd_data->bConfigurationValue, cd_data->wTotalLength);
 
 		// Cache the descriptor
 		priv->config_descriptor[i] = malloc(cd_data->wTotalLength);
-		if (priv->config_descriptor[i] == NULL)
-			LOOP_BREAK(LIBUSB_ERROR_NO_MEM);
-		memcpy(priv->config_descriptor[i], cd_data, cd_data->wTotalLength);
-	}
-
-	// Any failure will result in dev->num_configurations being forced to 0.
-	// We need to release any memory that may have been allocated for config
-	// descriptors that were successfully retrieved, otherwise that memory
-	// will be leaked
-	if (r != LIBUSB_SUCCESS) {
-		for (i = 0; i < dev->num_configurations; i++)
-			free(priv->config_descriptor[i]);
+		if (priv->config_descriptor[i] != NULL) {
+			memcpy(priv->config_descriptor[i], cd_data, cd_data->wTotalLength);
+		} else {
+			usbi_err(ctx, "could not allocate configuration descriptor %u buffer for '%s'", i, priv->dev_id);
+		}
 	}
-
-	return r;
 }
 
 /*
@@ -879,11 +869,8 @@ static int init_device(struct libusb_device *dev, struct libusb_device *parent_d
 		priv->active_config = conn_info.CurrentConfigurationValue;
 		usbi_dbg("found %u configurations (active conf: %u)", dev->num_configurations, priv->active_config);
 
-		// If we can't read the config descriptors, just set the number of confs to zero
-		if (cache_config_descriptors(dev, hub_handle) != LIBUSB_SUCCESS) {
-			dev->num_configurations = 0;
-			priv->dev_descriptor.bNumConfigurations = 0;
-		}
+		// Cache as many config descriptors as we can
+		cache_config_descriptors(dev, hub_handle);
 
 		// In their great wisdom, Microsoft decided to BREAK the USB speed report between Windows 7 and Windows 8
 		if (windows_version >= WINDOWS_8) {
@@ -1566,6 +1553,8 @@ static int winusb_get_config_descriptor_by_value(struct libusb_device *dev, uint
 
 	for (index = 0; index < dev->num_configurations; index++) {
 		config_header = priv->config_descriptor[index];
+		if (config_header == NULL)
+			continue;
 		if (config_header->bConfigurationValue == bConfigurationValue) {
 			*buffer = (unsigned char *)priv->config_descriptor[index];
 			return (int)config_header->wTotalLength;
diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index 346d835..482fb14 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11307
+#define LIBUSB_NANO 11308