I was about to submit this in a PR of my own, but noticed I've been beaten
to it.  :-)  Anyway, it seems the fix is in rev 1.36 of
syssrc/sys/kern/subr_extent.c and I was able to merge it via 'cvs -j1.35
-j1.36 subr_extent.c' into 1.5.  It looks like regress/sys/kern/extent/*
was pulled up into 1.5 without first pulling up the fix the new tests test
for in subr_extent.c.

//Jesse Off


Index: subr_extent.c
===================================================================
RCS file: /cvsroot/syssrc/sys/kern/subr_extent.c,v
retrieving revision 1.35
retrieving revision 1.36
diff -u -r1.35 -r1.36
--- subr_extent.c       2000/06/27 17:41:33     1.35
+++ subr_extent.c       2000/07/07 14:10:48     1.36
@@ -694,7 +694,7 @@
                                 * overflows, then the request
                                 * can't fit.
                                 */
-                               if (dontcross > ex->ex_end ||
+                               if (newstart + size - 1 > ex->ex_end ||
                                    dontcross < newstart)
                                        goto fail;
                        }
@@ -788,7 +788,7 @@
                         * overflows, then the request
                         * can't fit.
                         */
-                       if (dontcross > ex->ex_end ||
+                       if (newstart + size - 1 > ex->ex_end ||
                            dontcross < newstart)
                                goto fail;
                }