--- linux-2.6.28-rc4/mm/mmap.c	Mon Nov 10 01:36:15 2008
+++ linux-2.6.28-rc4.fix/mm/mmap.c	Wed Nov 12 01:21:39 2008
@@ -1704,7 +1704,7 @@
 	vma = find_vma_prev(mm, addr, &prev);
 	if (vma && (vma->vm_start <= addr))
 		return vma;
-	if (expand_stack(prev, addr))
+	if (!prev || expand_stack(prev, addr))
 		return NULL;
 	if (prev->vm_flags & VM_LOCKED) {
 		if (mlock_vma_pages_range(prev, addr, prev->vm_end) < 0)