Move desc_len sanity checks to start of loops

Author: GuavTek

src/host/usbh.c

@@ -1631,6 +1631,13 @@ static bool _parse_configuration_descriptor(uint8_t dev_addr, tusb_desc_configur
 
   // parse each interfaces
   while( p_desc < desc_end ) {
+    if ( 0 == tu_desc_len(p_desc) ) {
+      // A zero length descriptor indicates that the device is off spec (e.g. wrong wTotalLength).
+      // Parsed interfaces should still be usable
+      TU_LOG_USBH("Encountered a zero-length descriptor after %u bytes\r\n", (uint32_t)p_desc - (uint32_t)desc_cfg);
+      break;
+    }
+
     uint8_t assoc_itf_count = 1;
 
     // Class will always starts with Interface Association (if any) and then Interface descriptor
@@ -1645,13 +1652,6 @@ static bool _parse_configuration_descriptor(uint8_t dev_addr, tusb_desc_configur
       //          desc_iad->bFunctionClass  == desc_itf->bInterfaceClass);
     }
 
-    if ( 0 == tu_desc_len(p_desc) ) {
-      // A zero length descriptor indicates that the wTotalLength field is wrong.
-      // Parsed interfaces should still be usable
-      TU_LOG_USBH("Encountered a zero-length descriptor after %u bytes\r\n", (uint32_t)p_desc - (uint32_t)desc_cfg);
-      break;
-    }
-
     TU_ASSERT( TUSB_DESC_INTERFACE == tu_desc_type(p_desc) );
     tusb_desc_interface_t const* desc_itf = (tusb_desc_interface_t const*) p_desc;
 

src/tusb.c

@@ -247,6 +247,10 @@ uint16_t tu_desc_get_interface_total_len(tusb_desc_interface_t const* desc_itf,
     p_desc = tu_desc_next(p_desc);
 
     while (len < max_len) {
+      if (tu_desc_len(p_desc) == 0) {
+        // Escape infinite loop
+        break;
+      }
       // return on IAD regardless of itf count
       if (tu_desc_type(p_desc) == TUSB_DESC_INTERFACE_ASSOCIATION) {
         return len;
@@ -255,10 +259,6 @@ uint16_t tu_desc_get_interface_total_len(tusb_desc_interface_t const* desc_itf,
           ((tusb_desc_interface_t const*) p_desc)->bAlternateSetting == 0) {
         break;
       }
-      if (tu_desc_len(p_desc) == 0) {
-        // Escape infinite loop
-        break;
-      }
 
       len += tu_desc_len(p_desc);
       p_desc = tu_desc_next(p_desc);