From nobody Sat Apr 18 07:35:53 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 3A537C43334 for ; Fri, 15 Jul 2022 13:49:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230158AbiGONtk (ORCPT ); Fri, 15 Jul 2022 09:49:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50008 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229671AbiGONtj (ORCPT ); Fri, 15 Jul 2022 09:49:39 -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 6324525EA4 for ; Fri, 15 Jul 2022 06:49:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1657892977; 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=amabN4tTEMh+/YwAFG30tjFcz2ElQGektMQtXLodpFI=; b=PFwA2mHD6VSlTQHUBX0wXH77XzID2Hx+kAOYiRo6azs4DeIFWlqkk46rgWLwSQdOMvWq8/ HRBBF7PUr3GP8goqkgP0JFhWmrUuDX2IMsx0TV+4LszJwcxnDhG+d9XetqEf9DA+j9k/c4 4N73cWPOzgawtvmAVKL0Uf04YWLou74= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-660-Z4EXuOs0NA6ZvoCz4bRe6Q-1; Fri, 15 Jul 2022 09:49:26 -0400 X-MC-Unique: Z4EXuOs0NA6ZvoCz4bRe6Q-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 02723185A7A4; Fri, 15 Jul 2022 13:49:26 +0000 (UTC) Received: from pauld.bos.com (dhcp-17-237.bos.redhat.com [10.18.17.237]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7C6842166B26; Fri, 15 Jul 2022 13:49:25 +0000 (UTC) From: Phil Auld To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , "Rafael J . Wysocki" , Barry Song <21cnbao@gmail.com>, Tian Tao , Yury Norov , stable@vger.kernel.org Subject: [PATCH v5] drivers/base: fix userspace break from using bin_attributes for cpumap and cpulist Date: Fri, 15 Jul 2022 09:49:24 -0400 Message-Id: <20220715134924.3466194-1-pauld@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" Using bin_attributes with a 0 size causes fstat and friends to return that 0 size. This breaks userspace code that retrieves the size before reading the file. Rather than reverting 75bd50fa841 ("drivers/base/node.c: use bin_attribute to break the size limitation of cpumap ABI") let's put in a size value at compile time. For cpulist the maximum size is on the order of NR_CPUS * (ceil(log10(NR_CPUS)) + 1)/2 which for 8192 is 20480 (8192 * 5)/2. In order to get near that you'd need a system with every other CPU on one node. For example: (0,2,4,8, ... ). To simplify the math and support larger NR_CPUS in the future we are using (NR_CPUS * 7)/2. We also set it to a min of PAGE_SIZE to retain the older behavior for smaller NR_CPUS. The cpumap file the size works out to be NR_CPUS/4 + NR_CPUS/32 - 1 (or NR_CPUS * 9/32 - 1) including the ","s. Add a set of macros for these values to cpumask.h so they can be used in multiple places. Apply these to the handful of such files in drivers/base/topology.c as well as node.c. As an example, on an 80 cpu 4-node system (NR_CPUS =3D=3D 8192): before: -r--r--r--. 1 root root 0 Jul 12 14:08 system/node/node0/cpulist -r--r--r--. 1 root root 0 Jul 11 17:25 system/node/node0/cpumap after: -r--r--r--. 1 root root 28672 Jul 13 11:32 system/node/node0/cpulist -r--r--r--. 1 root root 4096 Jul 13 11:31 system/node/node0/cpumap CONFIG_NR_CPUS =3D 16384 -r--r--r--. 1 root root 57344 Jul 13 14:03 system/node/node0/cpulist -r--r--r--. 1 root root 4607 Jul 13 14:02 system/node/node0/cpumap The actual number of cpus doesn't matter for the reported size since they are based on NR_CPUS. Fixes: 75bd50fa841 ("drivers/base/node.c: use bin_attribute to break the si= ze limitation of cpumap ABI") Fixes: bb9ec13d156 ("topology: use bin_attribute to break the size limitati= on of cpumap ABI") Cc: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" Cc: Yury Norov Cc: stable@vger.kernel.org Signed-off-by: Phil Auld Acked-by: Yury Norov (for include/linux/cpumask.h) --- v2: Fix cpumap size calculation. Increase multiplier for cpulist size. v3: Add comments in code. v4: Define constants in cpumask.h. Move comments there. Also fix topology.c. v5: Fixed math based on Yury's corrections. drivers/base/node.c | 4 ++-- drivers/base/topology.c | 32 ++++++++++++++++---------------- include/linux/cpumask.h | 18 ++++++++++++++++++ 3 files changed, 36 insertions(+), 18 deletions(-) diff --git a/drivers/base/node.c b/drivers/base/node.c index 0ac6376ef7a1..eb0f43784c2b 100644 --- a/drivers/base/node.c +++ b/drivers/base/node.c @@ -45,7 +45,7 @@ static inline ssize_t cpumap_read(struct file *file, stru= ct kobject *kobj, return n; } =20 -static BIN_ATTR_RO(cpumap, 0); +static BIN_ATTR_RO(cpumap, CPUMAP_FILE_MAX_BYTES); =20 static inline ssize_t cpulist_read(struct file *file, struct kobject *kobj, struct bin_attribute *attr, char *buf, @@ -66,7 +66,7 @@ static inline ssize_t cpulist_read(struct file *file, str= uct kobject *kobj, return n; } =20 -static BIN_ATTR_RO(cpulist, 0); +static BIN_ATTR_RO(cpulist, CPULIST_FILE_MAX_BYTES); =20 /** * struct node_access_nodes - Access class device to hold user visible diff --git a/drivers/base/topology.c b/drivers/base/topology.c index ac6ad9ab67f9..89f98be5c5b9 100644 --- a/drivers/base/topology.c +++ b/drivers/base/topology.c @@ -62,47 +62,47 @@ define_id_show_func(ppin, "0x%llx"); static DEVICE_ATTR_ADMIN_RO(ppin); =20 define_siblings_read_func(thread_siblings, sibling_cpumask); -static BIN_ATTR_RO(thread_siblings, 0); -static BIN_ATTR_RO(thread_siblings_list, 0); +static BIN_ATTR_RO(thread_siblings, CPUMAP_FILE_MAX_BYTES); +static BIN_ATTR_RO(thread_siblings_list, CPULIST_FILE_MAX_BYTES); =20 define_siblings_read_func(core_cpus, sibling_cpumask); -static BIN_ATTR_RO(core_cpus, 0); -static BIN_ATTR_RO(core_cpus_list, 0); +static BIN_ATTR_RO(core_cpus, CPUMAP_FILE_MAX_BYTES); +static BIN_ATTR_RO(core_cpus_list, CPULIST_FILE_MAX_BYTES); =20 define_siblings_read_func(core_siblings, core_cpumask); -static BIN_ATTR_RO(core_siblings, 0); -static BIN_ATTR_RO(core_siblings_list, 0); +static BIN_ATTR_RO(core_siblings, CPUMAP_FILE_MAX_BYTES); +static BIN_ATTR_RO(core_siblings_list, CPULIST_FILE_MAX_BYTES); =20 #ifdef TOPOLOGY_CLUSTER_SYSFS define_siblings_read_func(cluster_cpus, cluster_cpumask); -static BIN_ATTR_RO(cluster_cpus, 0); -static BIN_ATTR_RO(cluster_cpus_list, 0); +static BIN_ATTR_RO(cluster_cpus, CPUMAP_FILE_MAX_BYTES); +static BIN_ATTR_RO(cluster_cpus_list, CPULIST_FILE_MAX_BYTES); #endif =20 #ifdef TOPOLOGY_DIE_SYSFS define_siblings_read_func(die_cpus, die_cpumask); -static BIN_ATTR_RO(die_cpus, 0); -static BIN_ATTR_RO(die_cpus_list, 0); +static BIN_ATTR_RO(die_cpus, CPUMAP_FILE_MAX_BYTES); +static BIN_ATTR_RO(die_cpus_list, CPULIST_FILE_MAX_BYTES); #endif =20 define_siblings_read_func(package_cpus, core_cpumask); -static BIN_ATTR_RO(package_cpus, 0); -static BIN_ATTR_RO(package_cpus_list, 0); +static BIN_ATTR_RO(package_cpus, CPUMAP_FILE_MAX_BYTES); +static BIN_ATTR_RO(package_cpus_list, CPULIST_FILE_MAX_BYTES); =20 #ifdef TOPOLOGY_BOOK_SYSFS define_id_show_func(book_id, "%d"); static DEVICE_ATTR_RO(book_id); define_siblings_read_func(book_siblings, book_cpumask); -static BIN_ATTR_RO(book_siblings, 0); -static BIN_ATTR_RO(book_siblings_list, 0); +static BIN_ATTR_RO(book_siblings, CPUMAP_FILE_MAX_BYTES); +static BIN_ATTR_RO(book_siblings_list, CPULIST_FILE_MAX_BYTES); #endif =20 #ifdef TOPOLOGY_DRAWER_SYSFS define_id_show_func(drawer_id, "%d"); static DEVICE_ATTR_RO(drawer_id); define_siblings_read_func(drawer_siblings, drawer_cpumask); -static BIN_ATTR_RO(drawer_siblings, 0); -static BIN_ATTR_RO(drawer_siblings_list, 0); +static BIN_ATTR_RO(drawer_siblings, CPUMAP_FILE_MAX_BYTES); +static BIN_ATTR_RO(drawer_siblings_list, CPULIST_FILE_MAX_BYTES); #endif =20 static struct bin_attribute *bin_attrs[] =3D { diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index fe29ac7cc469..4592d0845941 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -1071,4 +1071,22 @@ cpumap_print_list_to_buf(char *buf, const struct cpu= mask *mask, [0] =3D 1UL \ } } =20 +/* + * Provide a valid theoretical max size for cpumap and cpulist sysfs files + * to avoid breaking userspace which may allocate a buffer based on the si= ze + * reported by e.g. fstat. + * + * for cpumap NR_CPUS * 9/32 - 1 should be an exact length. + * + * For cpulist 7 is (ceil(log10(NR_CPUS)) + 1) allowing for NR_CPUS to be = up + * to 2 orders of magnitude larger than 8192. And then we divide by 2 to + * cover a worst-case of every other cpu being on one of two nodes for a + * very large NR_CPUS. + * + * Use PAGE_SIZE as a minimum for smaller configurations. + */ +#define CPUMAP_FILE_MAX_BYTES ((((NR_CPUS * 9)/32 - 1) > PAGE_SIZE) \ + ? (NR_CPUS * 9)/32 - 1 : PAGE_SIZE) +#define CPULIST_FILE_MAX_BYTES (((NR_CPUS * 7)/2 > PAGE_SIZE) ? (NR_CPUS = * 7)/2 : PAGE_SIZE) + #endif /* __LINUX_CPUMASK_H */ --=20 2.31.1