ovl: filter trusted xattr for non-admin

ovl: filter trusted xattr for non-admin

[ Upstream commit a082c6f680da298cf075886ff032f32ccb7c5e1a ]

Filesystems filter out extended attributes in the "trusted." domain for
unprivlieged callers.

Overlay calls underlying filesystem's method with elevated privs, so need
to do the filtering in overlayfs too.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[sw0312.kim: cherry-pick linux-4.4.y commit d88cbbe7ba0c to fix smack deny issue on overlayfs]
Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Change-Id: I3d7bb51db6e57d16f05fef56d65170aab9bb63f2