From patchwork Mon Mar 22 16:02:44 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Arnd Bergmann X-Patchwork-Id: 12155365 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=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 9106AC433F2 for ; Mon, 22 Mar 2021 16:05:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F66A619C5 for ; Mon, 22 Mar 2021 16:05:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231826AbhCVQFF (ORCPT ); Mon, 22 Mar 2021 12:05:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:52588 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231455AbhCVQEi (ORCPT ); Mon, 22 Mar 2021 12:04:38 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id DD9F06199F; Mon, 22 Mar 2021 16:04:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616429077; bh=yAy/I3E6cDxsmlVnV0YJAH5ZEQIRtNmu4zak4TbdMtM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=UB5shkw7Yd4R5EAaTaJbKCgGMQHdzM6i80uoGxhNLAKr58/Z+hb/X02iDZFbFM5q7 ohBr0mnuKE2zD2dZIPp5mGV/8upXxQjJIfPGJp9PdMs6uae5VNAC7zYBRMfKWnHX2T dVcWKQocYTTmbDcT2P/QpYMSgUNzpEBC5mOFpZCLPDNYvMuLPWfLzgAFpKC9vWx2UV WcW6Gm/cjDbzo+bVOJsKrlf8DWJ6XKsV5KO6yCyvx8yAazXnd03HJIpEKsAL1WBIyL rctKK7FEjfv0XP7F/8O3bxyOq6H75TM+jdZPPW1bjsoXOWVbf0YQRUVNLoyOj2UQzP uTGmECN+tjDoA== From: Arnd Bergmann To: linux-kernel@vger.kernel.org, Martin Sebor , Tejun Heo , Zefan Li , Johannes Weiner Cc: Arnd Bergmann , x86@kernel.org, Ning Sun , Jani Nikula , Kalle Valo , Simon Kelley , James Smart , "James E.J. Bottomley" , Anders Larsen , Serge Hallyn , Imre Deak , linux-arm-kernel@lists.infradead.org, tboot-devel@lists.sourceforge.net, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, ath11k@lists.infradead.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-scsi@vger.kernel.org, cgroups@vger.kernel.org, linux-security-module@vger.kernel.org, Roman Gushchin , Christian Brauner , Alexei Starovoitov , Andrii Nakryiko , Odin Ugedal , Cong Wang , =?utf-8?q?Michal_Koutn=C3=BD?= , Bhaskar Chowdhury Subject: [PATCH 06/11] cgroup: fix -Wzero-length-bounds warnings Date: Mon, 22 Mar 2021 17:02:44 +0100 Message-Id: <20210322160253.4032422-7-arnd@kernel.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210322160253.4032422-1-arnd@kernel.org> References: <20210322160253.4032422-1-arnd@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org From: Arnd Bergmann When cgroups are enabled, but every single subsystem is turned off, CGROUP_SUBSYS_COUNT is zero, and the cgrp->subsys[] array has no members. gcc-11 points out that this leads to an invalid access in any function that might access this array: kernel/cgroup/cgroup.c: In function 'cgroup_addrm_files': kernel/cgroup/cgroup.c:460:58: warning: array subscript '' is outside the bounds of an interior zero-length array 'struct cgroup_subsys_state *[0]' [-Wzero-length-bounds] kernel/cgroup/cgroup.c:460:24: note: in expansion of macro 'rcu_dereference_check' 460 | return rcu_dereference_check(cgrp->subsys[ss->id], | ^~~~~~~~~~~~~~~~~~~~~ In file included from include/linux/cgroup.h:28, from kernel/cgroup/cgroup-internal.h:5, from kernel/cgroup/cgroup.c:31: include/linux/cgroup-defs.h:422:43: note: while referencing 'subsys' 422 | struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT]; I'm not sure what is expected to happen for such a configuration, presumably these functions are never calls in that case. Adding a sanity check in each function we get the warning for manages to shut up the warnings and do nothing instead. Signed-off-by: Arnd Bergmann Reviewed-by: Michal Koutný --- I'm grouping this together with the -Wstringop-overread warnings, since the underlying logic in gcc seems to be the same. --- kernel/cgroup/cgroup.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 9153b20e5cc6..3477f1dc7872 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -456,7 +456,7 @@ static u16 cgroup_ss_mask(struct cgroup *cgrp) static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp, struct cgroup_subsys *ss) { - if (ss) + if (ss && (CGROUP_SUBSYS_COUNT > 0)) return rcu_dereference_check(cgrp->subsys[ss->id], lockdep_is_held(&cgroup_mutex)); else @@ -534,6 +534,9 @@ struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp, { struct cgroup_subsys_state *css; + if (CGROUP_SUBSYS_COUNT == 0) + return NULL; + do { css = cgroup_css(cgrp, ss); @@ -561,6 +564,9 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp, { struct cgroup_subsys_state *css; + if (CGROUP_SUBSYS_COUNT == 0) + return NULL; + rcu_read_lock(); do { @@ -630,7 +636,7 @@ struct cgroup_subsys_state *of_css(struct kernfs_open_file *of) * the matching css from the cgroup's subsys table is guaranteed to * be and stay valid until the enclosing operation is complete. */ - if (cft->ss) + if (cft->ss && CGROUP_SUBSYS_COUNT > 0) return rcu_dereference_raw(cgrp->subsys[cft->ss->id]); else return &cgrp->self; @@ -2343,6 +2349,9 @@ struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset, struct css_set *cset = tset->cur_cset; struct task_struct *task = tset->cur_task; + if (CGROUP_SUBSYS_COUNT == 0) + return NULL; + while (&cset->mg_node != tset->csets) { if (!task) task = list_first_entry(&cset->mg_tasks, @@ -4523,7 +4532,7 @@ void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags, it->ss = css->ss; it->flags = flags; - if (it->ss) + if (it->ss && CGROUP_SUBSYS_COUNT > 0) it->cset_pos = &css->cgroup->e_csets[css->ss->id]; else it->cset_pos = &css->cgroup->cset_links;