Index: uspace/lib/libc/generic/malloc.c
===================================================================
--- uspace/lib/libc/generic/malloc.c	(revision ed90317444652a29e89501a128d66020aaea52b5)
+++ uspace/lib/libc/generic/malloc.c	(revision e70edd172d2cf9046b75757402180d66ef63665f)
@@ -164,4 +164,7 @@
 {
 	if (size == 0)
+		return false;
+
+	if ((heap_start + size < heap_start) || (heap_end + size < heap_end))
 		return false;