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

This patch against 2.5.69-bk adds a hook to proc_pid_make_inode to allow
security modules to set the security attributes on /proc/pid inodes based on
the security attributes of the associated task.  This is required by SELinux
in order to control access to the process state accessible via /proc/pid
inodes in accordance with the task's security label.

An alternative approach that was considered was to implement an xattr handler
for /proc/pid inodes.  That approach would still require a hook call from the
xattr handler to the security module to obtain an xattr value based on the
task security attributes, so it would add a further level of
indirection/translation.  The only benefit of implementing an xattr handler
for the /proc/pid inodes would be that the /proc/pid inode security labels
could then be exported to userspace.  However, the /proc/pid inode security
labels are only used internally by the security module for access control
purposes, and userspace access to the full range of process attributes is
already provided via the /proc/pid/attr interface.  Consequently, a simple
hook in proc_pid_make_inode seemed preferable.