From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030237Ab2CMA0T (ORCPT ); Mon, 12 Mar 2012 20:26:19 -0400 Received: from mail.windriver.com ([147.11.1.11]:49112 "EHLO mail.windriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965073Ab2CMAZP (ORCPT ); Mon, 12 Mar 2012 20:25:15 -0400 From: Paul Gortmaker To: stable@kernel.org, linux-kernel@vger.kernel.org Cc: stable-review@kernel.org, Vasiliy Kulikov , Vasiliy Kulikov , Balbir Singh , Andrew Morton , Linus Torvalds , Paul Gortmaker Subject: [34-longterm 188/196] taskstats: don't allow duplicate entries in listener mode Date: Mon, 12 Mar 2012 20:21:41 -0400 Message-Id: <1331598109-31424-143-git-send-email-paul.gortmaker@windriver.com> X-Mailer: git-send-email 1.7.9.3 In-Reply-To: <1331598109-31424-1-git-send-email-paul.gortmaker@windriver.com> References: <1331597724-31358-1-git-send-email-paul.gortmaker@windriver.com> <1331598109-31424-1-git-send-email-paul.gortmaker@windriver.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vasiliy Kulikov ------------------- This is a commit scheduled for the next v2.6.34 longterm release. If you see a problem with using this for longterm, please comment. ------------------- commit 26c4caea9d697043cc5a458b96411b86d7f6babd upstream. Currently a single process may register exit handlers unlimited times. It may lead to a bloated listeners chain and very slow process terminations. Eg 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 Cc: Balbir Singh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Paul Gortmaker --- kernel/taskstats.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/kernel/taskstats.c b/kernel/taskstats.c index 11281d5..5e21645 100644 --- a/kernel/taskstats.c +++ b/kernel/taskstats.c @@ -292,16 +292,18 @@ 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; @@ -310,9 +312,16 @@ 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; } -- 1.7.9.3