From nobody Tue Apr 14 15:39:04 2026 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 E55F8C00140 for ; Wed, 3 Aug 2022 01:55:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234904AbiHCBzZ (ORCPT ); Tue, 2 Aug 2022 21:55:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33128 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233423AbiHCBzW (ORCPT ); Tue, 2 Aug 2022 21:55:22 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 46A78186D6 for ; Tue, 2 Aug 2022 18:55:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1659491720; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=HX8NATpwjkTcDpmelYUXYRI0qsy6slg8qubTweG5yEM=; b=MtYcmS8hwGBR9Qc+VzevvsNJlo7e077sbHA6qFsrSlIRkEQ7RUquI6dMVrzXKPM7oBCtDw ndHaUCDvD8ryxOGY0ig4rqlWKr2pmS79eh0Pkp/PxBOHrd1dnK+QMFCj9MAqxTtTCNDBPz 2j7Mxb3qMd4wcl25pIvsa5DpecUK0Ow= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-130-xp1F_XonMSCfCRwzY6-3vQ-1; Tue, 02 Aug 2022 21:55:16 -0400 X-MC-Unique: xp1F_XonMSCfCRwzY6-3vQ-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id DE7413806703; Wed, 3 Aug 2022 01:55:14 +0000 (UTC) Received: from llong.com (unknown [10.22.16.202]) by smtp.corp.redhat.com (Postfix) with ESMTP id 88DD92166B26; Wed, 3 Aug 2022 01:55:13 +0000 (UTC) From: Waiman Long To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Tejun Heo , Zefan Li , Johannes Weiner Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Waiman Long Subject: [PATCH] sched, cpuset: Fix dl_cpu_busy() panic due to empty cs->cpus_allowed Date: Tue, 2 Aug 2022 21:54:51 -0400 Message-Id: <20220803015451.2219567-1-longman@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" With cgroup v2, the cpuset's cpus_allowed mask can be empty indicating that the cpuset will just use the effective cpus of its parent. So cpuset_can_attach() can call task_can_attach() with an empty mask. This can lead to cpumask_any_and() returns nr_cpu_ids causing the call to dl_bw_of() to crash due to percpu value access of an out of bound cpu value. For example, [80468.182258] BUG: unable to handle page fault for address: ffffffff8b6648= b0 : [80468.191019] RIP: 0010:dl_cpu_busy+0x30/0x2b0 : [80468.207946] Call Trace: [80468.208947] cpuset_can_attach+0xa0/0x140 [80468.209953] cgroup_migrate_execute+0x8c/0x490 [80468.210931] cgroup_update_dfl_csses+0x254/0x270 [80468.211898] cgroup_subtree_control_write+0x322/0x400 [80468.212854] kernfs_fop_write_iter+0x11c/0x1b0 [80468.213777] new_sync_write+0x11f/0x1b0 [80468.214689] vfs_write+0x1eb/0x280 [80468.215592] ksys_write+0x5f/0xe0 [80468.216463] do_syscall_64+0x5c/0x80 [80468.224287] entry_SYSCALL_64_after_hwframe+0x44/0xae Fix that by using effective_cpus instead. For cgroup v1, effective_cpus is the same as cpus_allowed. For v2, effective_cpus is the real cpumask to be used by tasks within the cpuset anyway. Also update task_can_attach()'s 2nd argument name to cs_effective_cpus to reflect the change. In addition, a check is added to task_can_attach() to guard against the possibility that cpumask_any_and() may return a value >=3D nr_cpu_ids. Fixes: 7f51412a415d ("sched/deadline: Fix bandwidth check/update when migra= ting tasks between exclusive cpusets") Signed-off-by: Waiman Long Acked-by: Juri Lelli Reviewed-by: Michal Koutn=C3=BD --- include/linux/sched.h | 2 +- kernel/cgroup/cpuset.c | 2 +- kernel/sched/core.c | 8 +++++--- 3 files changed, 7 insertions(+), 5 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 88b8817b827d..6a060160f0db 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1813,7 +1813,7 @@ current_restore_flags(unsigned long orig_flags, unsig= ned long flags) } =20 extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, const stru= ct cpumask *trial); -extern int task_can_attach(struct task_struct *p, const struct cpumask *cs= _cpus_allowed); +extern int task_can_attach(struct task_struct *p, const struct cpumask *cs= _effective_cpus); #ifdef CONFIG_SMP extern void do_set_cpus_allowed(struct task_struct *p, const struct cpumas= k *new_mask); extern int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumas= k *new_mask); diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 71a418858a5e..58aadfda9b8b 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -2239,7 +2239,7 @@ static int cpuset_can_attach(struct cgroup_taskset *t= set) goto out_unlock; =20 cgroup_taskset_for_each(task, css, tset) { - ret =3D task_can_attach(task, cs->cpus_allowed); + ret =3D task_can_attach(task, cs->effective_cpus); if (ret) goto out_unlock; ret =3D security_task_setscheduler(task); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5555e49c4e12..addc3c2d2122 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8980,7 +8980,7 @@ int cpuset_cpumask_can_shrink(const struct cpumask *c= ur, } =20 int task_can_attach(struct task_struct *p, - const struct cpumask *cs_cpus_allowed) + const struct cpumask *cs_effective_cpus) { int ret =3D 0; =20 @@ -8999,9 +8999,11 @@ int task_can_attach(struct task_struct *p, } =20 if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span, - cs_cpus_allowed)) { - int cpu =3D cpumask_any_and(cpu_active_mask, cs_cpus_allowed); + cs_effective_cpus)) { + int cpu =3D cpumask_any_and(cpu_active_mask, cs_effective_cpus); =20 + if (unlikely(cpu >=3D nr_cpu_ids)) + return -EINVAL; ret =3D dl_cpu_busy(cpu, p); } =20 --=20 2.31.1