Linux: fix caching of guessed configuration
Reported and tested by Xiaofan Chen
diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index edf1545..1ed9ad8 100644
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -384,6 +384,8 @@
return r;
}
+/* cache the active config descriptor in memory. a value of -1 means that
+ * we aren't sure which one is active, so just assume the first one. */
static int cache_active_config(struct libusb_device *dev, int fd,
int active_config)
{
@@ -394,11 +396,15 @@
int idx;
int r;
- r = usbi_get_config_index_by_value(dev, active_config, &idx);
- if (r < 0)
- return r;
- if (idx == -1)
- return LIBUSB_ERROR_NOT_FOUND;
+ if (active_config == -1) {
+ idx = 0;
+ } else {
+ r = usbi_get_config_index_by_value(dev, active_config, &idx);
+ if (r < 0)
+ return r;
+ if (idx == -1)
+ return LIBUSB_ERROR_NOT_FOUND;
+ }
r = get_config_descriptor(fd, idx, tmp, sizeof(tmp));
if (r < 0) {