From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757431Ab3HGL2i (ORCPT ); Wed, 7 Aug 2013 07:28:38 -0400 Received: from cantor2.suse.de ([195.135.220.15]:54732 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753975Ab3HGL2h (ORCPT ); Wed, 7 Aug 2013 07:28:37 -0400 From: Michal Hocko To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Johannes Weiner , KAMEZAWA Hiroyuki , Andrew Morton , Tejun Heo , "Kirill A. Shutemov" , Anton Vorontsov Subject: [PATCH 1/3] memcg: limit the number of thresholds per-memcg Date: Wed, 7 Aug 2013 13:28:25 +0200 Message-Id: <1375874907-22013-1-git-send-email-mhocko@suse.cz> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is no limit for the maximum number of threshold events registered per memcg. This might lead to an user triggered memory depletion if a regular user is allowed to register on memory.[memsw.]usage_in_bytes eventfd interface. Let's be more strict and cap the number of events that might be registered. MAX_THRESHOLD_EVENTS value is more or less random. The expectation is that it should be high enough to cover reasonable usecases while not too high to allow excessive resources consumption. 1024 events consume something like 16KB which shouldn't be a big deal and it should be good enough. Reported-by: Tejun Heo Signed-off-by: Michal Hocko --- mm/memcontrol.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e4330cd..8247db3 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5401,6 +5401,9 @@ static void mem_cgroup_oom_notify(struct mem_cgroup *memcg) mem_cgroup_oom_notify_cb(iter); } +/* Maximum number of treshold events registered per memcg. */ +#define MAX_THRESHOLD_EVENTS 1024 + static int mem_cgroup_usage_register_event(struct cgroup *cgrp, struct cftype *cft, struct eventfd_ctx *eventfd, const char *args) { @@ -5424,6 +5427,11 @@ static int mem_cgroup_usage_register_event(struct cgroup *cgrp, else BUG(); + if (thresholds->primary->size == MAX_THRESHOLD_EVENTS) { + ret = -ENOSPC; + goto unlock; + } + usage = mem_cgroup_usage(memcg, type == _MEMSWAP); /* Check if a threshold crossed before adding a new one */ -- 1.7.10.4