Follows a trivial patch to check for RLIMIT_CPU to 0 in the right place.

diff -urN linux-2.6.20.3.orig/kernel/sys.c linux-2.6.20.3/kernel/sys.c
--- linux-2.6.20.3.orig/kernel/sys.c	2007-03-13 20:27:08.000000000 +0200
+++ linux-2.6.20.3/kernel/sys.c	2007-04-17 16:38:51.651236000 +0300
@@ -1916,6 +1916,16 @@
 	if (retval)
 		return retval;
 
+	if (resource == RLIMIT_CPU && new_rlim.rlim_cur == 0) {
+		/*
+		 * The caller is asking for an immediate RLIMIT_CPU
+		 * expiry.  But we use the zero value to mean "it was
+		 * never set".  So let's cheat and make it one second
+		 * instead
+		 */
+		new_rlim.rlim_cur = 1;
+	}
+
 	task_lock(current->group_leader);
 	*old_rlim = new_rlim;
 	task_unlock(current->group_leader);
@@ -1937,15 +1947,6 @@
 		unsigned long rlim_cur = new_rlim.rlim_cur;
 		cputime_t cputime;
 
-		if (rlim_cur == 0) {
-			/*
-			 * The caller is asking for an immediate RLIMIT_CPU
-			 * expiry.  But we use the zero value to mean "it was
-			 * never set".  So let's cheat and make it one second
-			 * instead
-			 */
-			rlim_cur = 1;
-		}
 		cputime = secs_to_cputime(rlim_cur);
 		read_lock(&tasklist_lock);
 		spin_lock_irq(&current->sighand->siglock);