Index: linux/kernel/pagg.c
===================================================================
--- linux/kernel/pagg.c	22 Aug 2004 01:19:59 -0000
+++ linux/kernel/pagg.c	8 Nov 2004 03:30:39 -0000
@@ -236,6 +236,8 @@
 		return -EINVAL;			/* error */
 	if (pagg_hook_new->name == NULL || strlen(pagg_hook_new->name) > PAGG_NAMELN)
 		return -EINVAL;			/* error */
+	if (!pagg_hook_new->attach || !pagg_hook_new->detach)
+		return -EINVAL;			/* error */		
 
 	/* Try to insert new hook entry into the pagg hook list */
 	down_write(&pagg_hook_list_sem);