diff -urNp 2.4.19pre9ac1/fs/locks.c 2.4.19pre9ac2/fs/locks.c
--- 2.4.19pre9ac1/fs/locks.c	Thu May 30 16:08:03 2002
+++ 2.4.19pre9ac2/fs/locks.c	Thu May 30 18:07:49 2002
@@ -273,9 +273,18 @@ static int flock_to_posix_lock(struct fi
 		return -EINVAL;
 	}
 
-	if (((start += l->l_start) < 0) || (l->l_len < 0))
+	/* POSIX-1996 leaves the case l->l_len < 0 undefined;
+	   POSIX-2001 defines it. */
+	start += l->l_start;
+	if (l->l_len < 0) {
+		end = start - 1;
+		start += l->l_len;
+	} else {
+		end = start + l->l_len - 1;
+	}
+
+	if (start < 0)
 		return -EINVAL;
-	end = start + l->l_len - 1;
 	if (l->l_len > 0 && end < 0)
 		return -EOVERFLOW;
 	fl->fl_start = start;	/* we record the absolute position */