From: Stephen Smalley <sds@epoch.ncsc.mil>

This patch against 2.5.68 implements an xattr handler for ext2 to support the
use of extended attributes by security modules for storing file security
labels.  As per the earlier discussion of extended attributes for security
modules, this handler uses a "security." prefix and allows for per-module
attribute names.  Security checking on userspace access to these attributes
can be performed by the security module using the LSM hooks in fs/xattr.c,
and the security module is free to internally use the inode operations
without restriction for managing its security labels.  Unlike the trusted
namespace, these labels are used internally for access control purposes by
the security module, and controls over userspace access to them require finer
granularity than capable() supports.