From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E56EC3A5A1 for ; Thu, 22 Aug 2019 12:29:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ED3F6206BB for ; Thu, 22 Aug 2019 12:29:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=android.com header.i=@android.com header.b="jo6+B+Np" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732778AbfHVM3z (ORCPT ); Thu, 22 Aug 2019 08:29:55 -0400 Received: from mail-wm1-f67.google.com ([209.85.128.67]:36064 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729212AbfHVM3y (ORCPT ); Thu, 22 Aug 2019 08:29:54 -0400 Received: by mail-wm1-f67.google.com with SMTP id g67so5591958wme.1 for ; Thu, 22 Aug 2019 05:29:52 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=android.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=gzVL8rDH4XSsN4Vadk8YEc7OcsBJCS9WRckj0x2C9Ng=; b=jo6+B+NpeyoMYop+k8YaZLPGyu9ng5kpuG+vz4e+uEg0XA4IL9M3+BxBzgSZRtGwL+ s+10j+X6pNtZhI76jyPX3eIodKSoF+pfFAW2rPFu29tImIAmnJJTCYkDEyCUOABrqpyM LRugCuLZzp3iC8q2r2yipyqL64I8DWruZ2rzGbWuRFG6MVxqgJ2zlv6HTMQ7bhiCFtza I1c1yW8oYEjln+Plulp2reEQMKP2rxVhajR/qoFVbfx8/UHcFcTPR99sOFk2DRuy81aC cW4T38dhHMttNZAzKzIJ22KOliC5ONTAih0rRMsp0TRXbE3RT9X/5r3dA4XdOOFG75aH ypAg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=gzVL8rDH4XSsN4Vadk8YEc7OcsBJCS9WRckj0x2C9Ng=; b=iFvQMgQEkXE6gepitqtV21RDqaeshGCht40WwRviBZ6EWvuupxW+zmPmLhTyqTIDoB LXXJeovCMe457V8mMA4czHIbeSlIJQyub+yDzybzgDAc8PBjwbi7vyrsqs1oBi+jtvYL JWs+tVaCDmHZnEZxubzmdRRJzFJ5FkTwAc5WxLIZ+++i6CEa3aFc3HSrhn+Cnh5zRWv/ AwmXwAkRiYyHz84AZjx8TurZgY+gQ9S71KwKO0563iWP8pH4fcztRdu1LuXHmKZxxGCY 9WZpiZPDU1fJnDFG06LgVHLyxi3SQq0Uroovrvd9kMZxOIrVr7bWH3ahHN0/ksv7Tlfl yNgw== X-Gm-Message-State: APjAAAXRC2FWEhPysRCFlP/l+lqAU5tRc/P3F+y3iq9CSoe9vtAWn9wH Ba1DOBs8k3dahgCnVUUSgwIdXQ== X-Google-Smtp-Source: APXvYqx4LnQ+mAcp8cDDK0S1ahpLGmUy9KpuKp1HNeHAho8YzwnoyQ3sHFxGNGxJWABsAzxcpmujPg== X-Received: by 2002:a1c:9950:: with SMTP id b77mr6301928wme.46.1566476991805; Thu, 22 Aug 2019 05:29:51 -0700 (PDT) Received: from google.com ([2a00:79e0:d:210:e751:37a0:1e95:e65d]) by smtp.gmail.com with ESMTPSA id f6sm54981340wrh.30.2019.08.22.05.29.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Aug 2019 05:29:51 -0700 (PDT) Date: Thu, 22 Aug 2019 13:29:49 +0100 From: Alessio Balsini To: Peter Zijlstra Cc: mingo@kernel.org, juri.lelli@redhat.com, linux-kernel@vger.kernel.org, dietmar.eggemann@arm.com, luca.abeni@santannapisa.it, bristot@redhat.com, dvyukov@google.com, tglx@linutronix.de, vpillai@digitalocean.com, rostedt@goodmis.org, kernel-team@android.com Subject: Re: [RFC][PATCH 01/13] sched/deadline: Impose global limits on sched_attr::sched_period Message-ID: <20190822122949.GA245353@google.com> References: <20190726145409.947503076@infradead.org> <20190726161357.397880775@infradead.org> <20190802172104.GA134279@google.com> <20190805115309.GJ2349@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190805115309.GJ2349@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 05, 2019 at 01:53:09PM +0200, Peter Zijlstra wrote: > > Like so? > Yes, that's exactly what I meant! What about this refactoring? Thanks, Alessio --- >From 459d5488acb3fac938b0f35f480a81a6e401ef92 Mon Sep 17 00:00:00 2001 From: Alessio Balsini Date: Thu, 22 Aug 2019 12:55:55 +0100 Subject: [PATCH] sched/deadline: Impose global limits on sched_attr::sched_period There are two DoS scenarios with SCHED_DEADLINE related to sched_attr::sched_period: - since access-control only looks at utilization and density, a very large period can allow a very large runtime, which in turn can incur a very large latency to lower priority tasks. - for very short periods we can end up spending more time programming the hardware timer than actually running the task. Mitigate these by imposing limits on the period. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Alessio Balsini --- include/linux/sched/sysctl.h | 7 +++++ kernel/sched/deadline.c | 51 ++++++++++++++++++++++++++++++++++-- kernel/sysctl.c | 14 ++++++++++ 3 files changed, 70 insertions(+), 2 deletions(-) diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h index d4f6215ee03f7..7c8ef07e52133 100644 --- a/include/linux/sched/sysctl.h +++ b/include/linux/sched/sysctl.h @@ -56,6 +56,13 @@ int sched_proc_update_handler(struct ctl_table *table, int write, extern unsigned int sysctl_sched_rt_period; extern int sysctl_sched_rt_runtime; +extern unsigned int sysctl_sched_dl_period_max; +extern unsigned int sysctl_sched_dl_period_min; + +extern int sched_dl_period_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, + loff_t *ppos); + #ifdef CONFIG_UCLAMP_TASK extern unsigned int sysctl_sched_uclamp_util_min; extern unsigned int sysctl_sched_uclamp_util_max; diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 0b9cbfb2b1d4f..fcdf70d9c0516 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -2640,6 +2640,42 @@ void __getparam_dl(struct task_struct *p, struct sched_attr *attr) attr->sched_flags = dl_se->flags; } +/* + * Default limits for DL period: on the top end we guard against small util + * tasks still getting ridiculous long effective runtimes, on the bottom end we + * guard against timer DoS. + */ +unsigned int sysctl_sched_dl_period_max = 1 << 22; /* ~4 seconds */ +unsigned int sysctl_sched_dl_period_min = 100; /* 100 us */ + +int sched_dl_period_handler(struct ctl_table *table, int write, + void __user *buffer, size_t *lenp, + loff_t *ppos) +{ + unsigned int old_max, old_min; + static DEFINE_MUTEX(mutex); + int ret; + + mutex_lock(&mutex); + old_max = sysctl_sched_dl_period_max; + old_min = sysctl_sched_dl_period_min; + + ret = proc_douintvec(table, write, buffer, lenp, ppos); + if (!ret && write) { + u64 max = (u64)sysctl_sched_dl_period_max * NSEC_PER_USEC; + u64 min = (u64)sysctl_sched_dl_period_min * NSEC_PER_USEC; + + if (min < 1ULL << DL_SCALE || max < min) { + sysctl_sched_dl_period_max = old_max; + sysctl_sched_dl_period_min = old_min; + ret = -EINVAL; + } + } + mutex_unlock(&mutex); + + return ret; +} + /* * This function validates the new parameters of a -deadline task. * We ask for the deadline not being zero, and greater or equal @@ -2652,6 +2688,8 @@ void __getparam_dl(struct task_struct *p, struct sched_attr *attr) */ bool __checkparam_dl(const struct sched_attr *attr) { + u64 period, max, min; + /* special dl tasks don't actually use any parameter */ if (attr->sched_flags & SCHED_FLAG_SUGOV) return true; @@ -2675,12 +2713,21 @@ bool __checkparam_dl(const struct sched_attr *attr) attr->sched_period & (1ULL << 63)) return false; + period = attr->sched_period; + if (!period) + period = attr->sched_deadline; + /* runtime <= deadline <= period (if period != 0) */ - if ((attr->sched_period != 0 && - attr->sched_period < attr->sched_deadline) || + if (period < attr->sched_deadline || attr->sched_deadline < attr->sched_runtime) return false; + max = (u64)READ_ONCE(sysctl_sched_dl_period_max) * NSEC_PER_USEC; + min = (u64)READ_ONCE(sysctl_sched_dl_period_min) * NSEC_PER_USEC; + + if (period < min || period > max) + return false; + return true; } diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 078950d9605ba..0d07e4707e9d2 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -442,6 +442,20 @@ static struct ctl_table kern_table[] = { .mode = 0644, .proc_handler = sched_rt_handler, }, + { + .procname = "sched_deadline_period_max_us", + .data = &sysctl_sched_dl_period_max, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = sched_dl_period_handler, + }, + { + .procname = "sched_deadline_period_min_us", + .data = &sysctl_sched_dl_period_min, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = sched_dl_period_handler, + }, { .procname = "sched_rr_timeslice_ms", .data = &sysctl_sched_rr_timeslice, -- 2.23.0.187.g17f5b7556c-goog