[PATCH] selinux: disable setxattr on mountpoint labeled filesystems

This patch disables the setting of SELinux xattrs on files created in
filesystems labeled via mountpoint labeling (mounted with the context=
option).  selinux_inode_setxattr already prevents explicit setxattr from
userspace on such filesystems, so this provides consistent behavior for
file creation.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>