sched: move no_new_privs into new atomic flags

Since seccomp transitions between threads requires updates to the
no_new_privs flag to be atomic, the flag must be part of an atomic flag
set. This moves the nnp flag into a separate task field, and introduces
accessors.

Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Andy Lutomirski <luto@amacapital.net>

security/apparmor/domain.c

@@ -621,7 +621,7 @@ int aa_change_hat(const char *hats[], int count, u64 token, bool permtest)
 	 * There is no exception for unconfined as change_hat is not
 	 * available.
 	 */
-	if (current->no_new_privs)
+	if (task_no_new_privs(current))
 		return -EPERM;
 
 	/* released below */
@@ -776,7 +776,7 @@ int aa_change_profile(const char *ns_name, const char *hname, bool onexec,
 	 * no_new_privs is set because this aways results in a reduction
 	 * of permissions.
 	 */
-	if (current->no_new_privs && !unconfined(profile)) {
+	if (task_no_new_privs(current) && !unconfined(profile)) {
 		put_cred(cred);
 		return -EPERM;
 	}