Index: /trunk/src/VBox/Devices/Network/DevE1000.cpp
===================================================================
--- /trunk/src/VBox/Devices/Network/DevE1000.cpp	(revision 82363)
+++ /trunk/src/VBox/Devices/Network/DevE1000.cpp	(revision 82364)
@@ -3933,4 +3933,6 @@
     /* We've already loaded pThis->nTxDFetched descriptors past TDH. */
     unsigned nDescsAvailable    = e1kGetTxLen(pThis) - pThis->nTxDFetched;
+    /* The following two lines ensure that pThis->nTxDFetched never overflows. */
+    AssertCompile(E1K_TXD_CACHE_SIZE < (256 * sizeof(pThis->nTxDFetched)));
     unsigned nDescsToFetch      = RT_MIN(nDescsAvailable, E1K_TXD_CACHE_SIZE - pThis->nTxDFetched);
     unsigned nDescsTotal        = TDLEN / sizeof(E1KTXDESC);
@@ -3960,5 +3962,5 @@
                  TDBAH, TDBAL));
     }
-    pThis->nTxDFetched += nDescsToFetch;
+    pThis->nTxDFetched += (uint8_t)nDescsToFetch;
     return nDescsToFetch;
 }