This patch is against 2.5.2-pre9 and is available at
http://prdownloads.sourceforge.net/user-mode-linux/uml-patch-2.5.2-pre9.bz2
It's also available from the other UML mirrors - they are listed at
http://user-mode-linux.sourceforge.net/dl-sf.html
This UML is the same as the 2.4.17-4 patch.
Jeff