diff --git a/mm/nommu.c b/mm/nommu.c
index 298884d..1898b2fe 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -282,6 +282,10 @@
 
 long vread(char *buf, char *addr, unsigned long count)
 {
+	/* Don't allow overflow */
+	if ((unsigned long) buf + count < count)
+		count = -(unsigned long) buf;
+
 	memcpy(buf, addr, count);
 	return count;
 }