--- vfs_mount.c.orig	Thu Dec 11 14:01:58 2003
+++ vfs_mount.c	Thu Dec 11 14:38:45 2003
@@ -68,6 +68,7 @@
 #include <sys/param.h>
 #include <sys/conf.h>
 #include <sys/cons.h>
+#include <sys/jail.h>
 #include <sys/kernel.h>
 #include <sys/linker.h>
 #include <sys/mac.h>
@@ -1013,6 +1014,12 @@
 	struct mount *mp;
 	char *pathbuf;
 	int error, id0, id1;
+
+	/*
+	 * Unmount operation is not permitted inside jail.
+	 */
+	if (jailed(td->td_ucred))
+		return (EPERM);
 
 	pathbuf = malloc(MNAMELEN, M_TEMP, M_WAITOK);
 	error = copyinstr(uap->path, pathbuf, MNAMELEN, NULL);