Index: vm_map.c
===================================================================
--- vm_map.c
+++ vm_map.c
@@ -2472,9 +2472,7 @@
 
 	VM_MAP_RANGE_CHECK(map, start, end);
 
-	if (vm_map_lookup_entry(map, start, &entry)) {
-		vm_map_clip_start(map, entry, start);
-	} else {
+	if (!vm_map_lookup_entry(map, start, &entry)) {
 		entry = entry->next;
 	}
 
@@ -2516,9 +2514,6 @@
 	 * breakpoint on text segment)
 	 */
 	for (current = entry; current->start < end; current = current->next) {
-
-		vm_map_clip_end(map, current, end);
-
 		if (set_max ||
 		    ((new_prot & ~(current->protection)) & VM_PROT_WRITE) == 0 ||
 		    ENTRY_CHARGED(current) ||
@@ -2530,7 +2525,8 @@
 		obj = current->object.vm_object;
 
 		if (obj == NULL || (current->eflags & MAP_ENTRY_NEEDS_COPY)) {
-			if (!swap_reserve(current->end - current->start)) {
+			if (!swap_reserve(MIN(end, current->end) -
+			    MAX(start, current->start))) {
 				vm_map_unlock(map);
 				return (KERN_RESOURCE_SHORTAGE);
 			}
@@ -2566,10 +2562,14 @@
 	}
 
 	/*
-	 * Go back and fix up protections. [Note that clipping is not
-	 * necessary the second time.]
+	 * Go back and fix up protections.
 	 */
+	if (entry->start < start)
+		vm_map_clip_start(map, entry, start);
 	for (current = entry; current->start < end; current = current->next) {
+
+		vm_map_clip_end(map, current, end);
+
 		if ((current->eflags & MAP_ENTRY_GUARD) != 0)
 			continue;