diff -rup qemu-kvm-0.15.1/hw/e1000.c me/hw/e1000.c
--- qemu-kvm-0.15.1/hw/e1000.c	2011-10-19 09:54:48.000000000 -0400
+++ me/hw/e1000.c	2012-05-29 09:28:15.832104874 -0400
@@ -472,6 +472,8 @@ process_tx_desc(E1000State *s, struct e1
             bytes = split_size;
             if (tp->size + bytes > msh)
                 bytes = msh - tp->size;
+
+            bytes = MIN(sizeof(tp->data) - tp->size, bytes);
             cpu_physical_memory_read(addr, tp->data + tp->size, bytes);
             if ((sz = tp->size + bytes) >= hdr && tp->size < hdr)
                 memmove(tp->header, tp->data, hdr);
@@ -487,6 +489,7 @@ process_tx_desc(E1000State *s, struct e1
         // context descriptor TSE is not set, while data descriptor TSE is set
         DBGOUT(TXERR, "TCP segmentaion Error\n");
     } else {
+        split_size = MIN(sizeof(tp->data) - tp->size, split_size);
         cpu_physical_memory_read(addr, tp->data + tp->size, split_size);
         tp->size += split_size;
     }