From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756527Ab1FPP4M (ORCPT ); Thu, 16 Jun 2011 11:56:12 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:48316 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754820Ab1FPP4E (ORCPT ); Thu, 16 Jun 2011 11:56:04 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:from:to:cc:subject:date:message-id:x-mailer; b=EkoFadcASN6Q3nPhI9JIARCfqBvoNylnusYHoO6uKF+fN+yp1r25T767MZzWbwZvkC WawGt6gryBKJxk4QFNLmcdNz55mJIJSmYwU9A5mRlpC2S+qpCindDaET/JQ6yeugsTZO U7w59LTmJKwBx2zzSagwJzD8qg5Cj/veU1sHY= From: Vasiliy Kulikov To: linux-kernel@vger.kernel.org Cc: Vasiliy Kulikov , Balbir Singh Subject: [PATCH v2] taskstats: don't allow duplicate entries in listener mode Date: Thu, 16 Jun 2011 19:55:59 +0400 Message-Id: <1308239759-4797-1-git-send-email-segoon@openwall.com> X-Mailer: git-send-email 1.7.0.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Currently a single process may register exit handlers unlimited times. It may lead to a bloated listeners chain and very slow process terminations. E.g. after 10KK sent TASKSTATS_CMD_ATTR_REGISTER_CPUMASKs ~300 Mb of kernel memory is stolen for the handlers chain and "time id" shows 2-7 seconds instead of normal 0.003. It makes it possible to exhaust all kernel memory and to eat much of CPU time by triggerring numerous exits on a single CPU. The patch limits the number of times a single process may register itself on a single CPU to one. One little issue is kept unfixed - as taskstats_exit() is called before exit_files() in do_exit(), the orphaned listener entry (if it was not explicitly deregistered) is kept until the next someone's exit() and implicit deregistration in send_cpu_listeners(). So, if a process registered itself as a listener exits and the next spawned process gets the same pid, it would inherit taskstats attributes. Signed-off-by: Vasiliy Kulikov --- v2 - removed wrong "From" line. kernel/taskstats.c | 15 ++++++++++++--- 1 files changed, 12 insertions(+), 3 deletions(-) diff --git a/kernel/taskstats.c b/kernel/taskstats.c index 9ffea36..fc0f220 100644 --- a/kernel/taskstats.c +++ b/kernel/taskstats.c @@ -285,16 +285,18 @@ ret: static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd) { struct listener_list *listeners; - struct listener *s, *tmp; + struct listener *s, *tmp, *s2; unsigned int cpu; if (!cpumask_subset(mask, cpu_possible_mask)) return -EINVAL; + s = NULL; if (isadd == REGISTER) { for_each_cpu(cpu, mask) { - s = kmalloc_node(sizeof(struct listener), GFP_KERNEL, - cpu_to_node(cpu)); + if (!s) + s = kmalloc_node(sizeof(struct listener), + GFP_KERNEL, cpu_to_node(cpu)); if (!s) goto cleanup; s->pid = pid; @@ -303,9 +305,16 @@ static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd) listeners = &per_cpu(listener_array, cpu); down_write(&listeners->sem); + list_for_each_entry_safe(s2, tmp, &listeners->list, list) { + if (s2->pid == pid) + goto next_cpu; + } list_add(&s->list, &listeners->list); + s = NULL; +next_cpu: up_write(&listeners->sem); } + kfree(s); return 0; } -- 1.7.0.4