apparmor: fix rlimit for posix cpu timers

Posix cpu timers requires an additional step beyond setting the rlimit.
Refactor the code so its clear when what code is setting the
limit and conditionally update the posix cpu timers when appropriate.

Fixes: baa73d9e47 ("posix-timers: Make them configurable")
Reviewed-by: Georgia Garcia <georgia.garcia@canonical.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>

security/apparmor/resource.c

@@ -196,6 +196,11 @@ void __aa_transition_rlimits(struct aa_label *old_l, struct aa_label *new_l)
 					     rules->rlimits.limits[j].rlim_max);
 			/* soft limit should not exceed hard limit */
 			rlim->rlim_cur = min(rlim->rlim_cur, rlim->rlim_max);
+			if (j == RLIMIT_CPU &&
+			    rlim->rlim_cur != RLIM_INFINITY &&
+			    IS_ENABLED(CONFIG_POSIX_TIMERS))
+				(void) update_rlimit_cpu(current->group_leader,
+							 rlim->rlim_cur);
 		}
 	}
 }