--- linux-2.4.20-oM3-orig/mm/mremap.c	Wed Mar 31 12:41:23 2004
+++ linux-2.4.20-oM3-mod/mm/mremap.c	Wed Mar 31 13:18:12 2004
@@ -182,6 +182,8 @@
 	}
 
 	if (!move_page_tables(current->mm, new_addr, addr, old_len)) {
+		unsigned long vm_locked = vma->vm_flags & VM_LOCKED;
+
 		if (allocated_vma) {
 			*new_vma = *vma;
 			new_vma->vm_start = new_addr;
@@ -200,10 +202,11 @@
 		 */
 		do_munmap(current->mm, addr, old_len, 0);
 		current->mm->total_vm += new_len >> PAGE_SHIFT;
-		if (new_vma->vm_flags & VM_LOCKED) {
+		if (vm_locked) {
 			current->mm->locked_vm += new_len >> PAGE_SHIFT;
-			make_pages_present(new_vma->vm_start,
-					   new_vma->vm_end);
+			if (new_len > old_len)
+				make_pages_present(new_addr + old_len,
+						   new_addr + new_len);
 		}
 		return new_addr;
 	}
@@ -252,6 +255,13 @@
 
 		if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
 			goto out;
+		/*
+		 * Allow new_len == 0 only if new_addr == addr
+		 * to preserve truncation in place (that was working
+		 * safe and some app may depend on it).
+		 */
+		if (unlikely(!new_len && new_addr != addr))
+			goto out;
 
 		/* Check if the location we're moving into overlaps the
 		 * old location at all, and fail if it does.
@@ -262,7 +272,9 @@
 		if ((addr <= new_addr) && (addr+old_len) > new_addr)
 			goto out;
 
-		do_munmap(current->mm, new_addr, new_len, 1);
+		ret = do_munmap(current->mm, new_addr, new_len, 1);
+		if (ret && new_len)
+			goto out;
 	}
 
 	/*
@@ -270,9 +282,11 @@
 	 * the unnecessary pages..
 	 * do_munmap does all the needed commit accounting
 	 */
-	ret = addr;
-	if (old_len >= new_len) {
-		do_munmap(current->mm, addr+new_len, old_len - new_len, 1);
+ 	if (old_len >= new_len) {
+		ret = do_munmap(current->mm, addr+new_len, old_len - new_len, 1);
+		if (ret && old_len != new_len)
+			goto out;
+		ret = addr;
 		if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 			goto out;
 	}