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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BAC87C4332F for ; Mon, 7 Mar 2022 10:11:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234023AbiCGKMl (ORCPT ); Mon, 7 Mar 2022 05:12:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47284 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242131AbiCGKLP (ORCPT ); Mon, 7 Mar 2022 05:11:15 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 09FAB887A4; Mon, 7 Mar 2022 01:54:30 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1E6176092A; Mon, 7 Mar 2022 09:54:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 256F5C340E9; Mon, 7 Mar 2022 09:54:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1646646868; bh=/P+khQUCz1gjLADcUzL6/3+TSXlLSdClqooalGmBoUk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b/d+3JD2V7GVBJqJf5Trxw6xuzxbJdFR0rDUQfhGIY73iobBvTUGD1Kkl6b0mommG ypGN2rDWUVLWLJZb9fT7WCemkEgzkB2TrrKazLVJ5OOtJ+LfoHzJUDVcah26MVaIf/ RLuSWPW30JpVC4zY3uJzEUxNB/+iaGYGGgpjWjQc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Linus Torvalds , "Peter Zijlstra (Intel)" , Tadeusz Struk , Zhang Qiao , Dietmar Eggemann Subject: [PATCH 5.16 119/186] sched: Fix yet more sched_fork() races Date: Mon, 7 Mar 2022 10:19:17 +0100 Message-Id: <20220307091657.406205277@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220307091654.092878898@linuxfoundation.org> References: <20220307091654.092878898@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Peter Zijlstra commit b1e8206582f9d680cff7d04828708c8b6ab32957 upstream. Where commit 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group") fixed a fork race vs cgroup, it opened up a race vs syscalls by not placing the task on the runqueue before it gets exposed through the pidhash. Commit 13765de8148f ("sched/fair: Fix fault in reweight_entity") is trying to fix a single instance of this, instead fix the whole class of issues, effectively reverting this commit. Fixes: 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group") Reported-by: Linus Torvalds Signed-off-by: Peter Zijlstra (Intel) Tested-by: Tadeusz Struk Tested-by: Zhang Qiao Tested-by: Dietmar Eggemann Link: https://lkml.kernel.org/r/YgoeCbwj5mbCR0qA@hirez.programming.kicks-ass.net Signed-off-by: Greg Kroah-Hartman --- include/linux/sched/task.h | 4 ++-- kernel/fork.c | 13 ++++++++++++- kernel/sched/core.c | 34 +++++++++++++++++++++------------- 3 files changed, 35 insertions(+), 16 deletions(-) --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -54,8 +54,8 @@ extern asmlinkage void schedule_tail(str extern void init_idle(struct task_struct *idle, int cpu); extern int sched_fork(unsigned long clone_flags, struct task_struct *p); -extern void sched_post_fork(struct task_struct *p, - struct kernel_clone_args *kargs); +extern void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs); +extern void sched_post_fork(struct task_struct *p); extern void sched_dead(struct task_struct *p); void __noreturn do_task_dead(void); --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2294,6 +2294,17 @@ static __latent_entropy struct task_stru goto bad_fork_put_pidfd; /* + * Now that the cgroups are pinned, re-clone the parent cgroup and put + * the new task on the correct runqueue. All this *before* the task + * becomes visible. + * + * This isn't part of ->can_fork() because while the re-cloning is + * cgroup specific, it unconditionally needs to place the task on a + * runqueue. + */ + sched_cgroup_fork(p, args); + + /* * From this point on we must avoid any synchronous user-space * communication until we take the tasklist-lock. In particular, we do * not want user-space to be able to predict the process start-time by @@ -2402,7 +2413,7 @@ static __latent_entropy struct task_stru fd_install(pidfd, pidfile); proc_fork_connector(p); - sched_post_fork(p, args); + sched_post_fork(p); cgroup_post_fork(p, args); perf_event_fork(p); --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1203,9 +1203,8 @@ int tg_nop(struct task_group *tg, void * } #endif -static void set_load_weight(struct task_struct *p) +static void set_load_weight(struct task_struct *p, bool update_load) { - bool update_load = !(READ_ONCE(p->__state) & TASK_NEW); int prio = p->static_prio - MAX_RT_PRIO; struct load_weight *load = &p->se.load; @@ -4393,7 +4392,7 @@ int sched_fork(unsigned long clone_flags p->static_prio = NICE_TO_PRIO(0); p->prio = p->normal_prio = p->static_prio; - set_load_weight(p); + set_load_weight(p, false); /* * We don't need the reset flag anymore after the fork. It has @@ -4411,6 +4410,7 @@ int sched_fork(unsigned long clone_flags init_entity_runnable_average(&p->se); + #ifdef CONFIG_SCHED_INFO if (likely(sched_info_on())) memset(&p->sched_info, 0, sizeof(p->sched_info)); @@ -4426,18 +4426,23 @@ int sched_fork(unsigned long clone_flags return 0; } -void sched_post_fork(struct task_struct *p, struct kernel_clone_args *kargs) +void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs) { unsigned long flags; -#ifdef CONFIG_CGROUP_SCHED - struct task_group *tg; -#endif + /* + * Because we're not yet on the pid-hash, p->pi_lock isn't strictly + * required yet, but lockdep gets upset if rules are violated. + */ raw_spin_lock_irqsave(&p->pi_lock, flags); #ifdef CONFIG_CGROUP_SCHED - tg = container_of(kargs->cset->subsys[cpu_cgrp_id], - struct task_group, css); - p->sched_task_group = autogroup_task_group(p, tg); + if (1) { + struct task_group *tg; + tg = container_of(kargs->cset->subsys[cpu_cgrp_id], + struct task_group, css); + tg = autogroup_task_group(p, tg); + p->sched_task_group = tg; + } #endif rseq_migrate(p); /* @@ -4448,7 +4453,10 @@ void sched_post_fork(struct task_struct if (p->sched_class->task_fork) p->sched_class->task_fork(p); raw_spin_unlock_irqrestore(&p->pi_lock, flags); +} +void sched_post_fork(struct task_struct *p) +{ uclamp_post_fork(p); } @@ -6880,7 +6888,7 @@ void set_user_nice(struct task_struct *p put_prev_task(rq, p); p->static_prio = NICE_TO_PRIO(nice); - set_load_weight(p); + set_load_weight(p, true); old_prio = p->prio; p->prio = effective_prio(p); @@ -7171,7 +7179,7 @@ static void __setscheduler_params(struct */ p->rt_priority = attr->sched_priority; p->normal_prio = normal_prio(p); - set_load_weight(p); + set_load_weight(p, true); } /* @@ -9410,7 +9418,7 @@ void __init sched_init(void) #endif } - set_load_weight(&init_task); + set_load_weight(&init_task, false); /* * The boot idle thread does lazy MMU switching as well: