See http://bugzilla.kernel.org/show_bug.cgi?id=6617.

This function dereference a __user pointer.
Signed-off-by: Philippe Retornaz <couriousous@mandriva.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>