diff -urNp --exclude CVS --exclude BitKeeper --exclude {arch} --exclude .arch-ids x-ref/mm/mremap.c x/mm/mremap.c
--- x-ref/mm/mremap.c	2004-02-21 18:12:06.723850824 +0100
+++ x/mm/mremap.c	2004-02-21 18:12:50.319223320 +0100
@@ -279,6 +279,13 @@ unsigned long do_mremap(unsigned long ad
 
 		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.
@@ -289,7 +296,9 @@ unsigned long do_mremap(unsigned long ad
 		if ((addr <= new_addr) && (addr+old_len) > new_addr)
 			goto out;
 
-		do_munmap(current->mm, new_addr, new_len);
+		ret = do_munmap(current->mm, new_addr, new_len);
+		if (ret && new_len)
+			goto out;
 	}
 
 	/*
@@ -298,7 +307,10 @@ unsigned long do_mremap(unsigned long ad
 	 */
 	ret = addr;
 	if (old_len >= new_len) {
-		do_munmap(current->mm, addr+new_len, old_len - new_len);
+		ret = do_munmap(current->mm, addr+new_len, old_len - new_len);
+		if (ret && old_len != new_len)
+			goto out;
+		ret = addr;
 		if (!(flags & MREMAP_FIXED) || (new_addr == addr))
 			goto out;
 	}