From nobody Sat Apr 18 11:01:56 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 0124EC43334 for ; Thu, 14 Jul 2022 18:30:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240747AbiGNSai (ORCPT ); Thu, 14 Jul 2022 14:30:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240731AbiGNSaa (ORCPT ); Thu, 14 Jul 2022 14:30:30 -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 12BAA6B742 for ; Thu, 14 Jul 2022 11:30:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1657823427; 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=8ToowepmwkG2i1N8S6l/4CuZCRFgwgJIWHsB4NCyi8Y=; b=C9iOVX8CuTM14+2WU95mjYFxElXW3T4fZQCDbzAKJFlmWYpzw5sGFtlwJi0/5yWT9bkBfB UrklDT03y8iysLhtTdQAY3oFaDzr8oeJAPSl28RrsYjdgmX7A18qdMu/itHFbu1whsR56U ArSENXw85yrX8nEytyQuN42i4FQgyxU= 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-588-E2CU-t6XPtCeCAzAcWUzrw-1; Thu, 14 Jul 2022 14:30:23 -0400 X-MC-Unique: E2CU-t6XPtCeCAzAcWUzrw-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BA2462813D34; Thu, 14 Jul 2022 18:30:22 +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 4DCCA401E54; Thu, 14 Jul 2022 18:30:22 +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 Subject: [PATCH v4 RESEND] drivers/base: fix userspace break from using bin_attributes for cpumap and cpulist Date: Thu, 14 Jul 2022 14:30:21 -0400 Message-Id: <20220714183021.2924119-1-pauld@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.85 on 10.11.54.10 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 brea= k the size limitation of cpumap ABI") let's put in a size value at compile time. Use d= irect comparison and a worst-case maximum to ensure compile time constants. For c= pulist the max is on the order of NR_CPUS * (ceil(log10(NR_CPUS)) + 1) which for 8192 = is 40960 (8192 * 5). In order to get near that you'd need a system with every other = CPU on one node or something similar. e.g. (0,2,4,8, ... ). To simplify the math and s= upport larger NR_CPUS in the future we are using NR_CPUS * 7. We also set it to a = min of PAGE_SIZE to retain the older behavior for smaller NR_CPUS. The cpumap file= wants to be something like NR_CPUS/4 + NR_CPUS/32, for the ","s so for simplicity we= are using NR_CPUS/2. Add a set of macros for these values to cpumask.h so they can be used in mu= ltiple places. Apply these to the handful of such files in drivers/base/topology.c as well= as node.c. On an 80 cpu 4-node sytem (NR_CPUS =3D=3D 8192) before: -r--r--r--. 1 root root 0 Jul 12 14:08 /sys/devices/system/node/node0/cpuli= st -r--r--r--. 1 root root 0 Jul 11 17:25 /sys/devices/system/node/node0/cpumap after: -r--r--r--. 1 root root 57344 Jul 13 11:32 /sys/devices/system/node/node0/c= pulist -r--r--r--. 1 root root 4096 Jul 13 11:31 /sys/devices/system/node/node0/c= pumap CONFIG_NR_CPUS =3D 16384 -r--r--r--. 1 root root 114688 Jul 13 14:03 /sys/devices/system/node/node0/= cpulist -r--r--r--. 1 root root 8192 Jul 13 14:02 /sys/devices/system/node/node0/= cpumap 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" Signed-off-by: Phil Auld --- 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. drivers/base/node.c | 4 ++-- drivers/base/topology.c | 32 ++++++++++++++++---------------- include/linux/cpumask.h | 16 ++++++++++++++++ 3 files changed, 34 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..007acdb462bd 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -1071,4 +1071,20 @@ cpumap_print_list_to_buf(char *buf, const struct cpu= mask *mask, [0] =3D 1UL \ } } =20 +/*=20 + * Provide a valid theoretical max size for cpumap ands cpulist sysfs file= s to=20 + * avoid breaking userspace which may allocate a buffer based on the size=20 + * reported by e.g. fstat. + * + * For cpumap NR_CPUS/2 is a simplification of NR_CPUS/4 + NR_CPUS/32.=20 + * + * For cpulist 7 is (ceil(log10(NR_CPUS)) + 1) allowing for NR_CPUS to be = up to=20 + * 2 orders of magnitude larger than 8192. This covers a worst-case of eve= ry=20 + * other cpu being on one of two nodes for a very large NR_CPUS. + * + * Use PAGE_SIZE as a minimum for smaller configurations.=20 + */ +#define CPUMAP_FILE_MAX_BYTES (((NR_CPUS >> 1) > PAGE_SIZE) ? NR_CPUS >> = 1 : PAGE_SIZE) +#define CPULIST_FILE_MAX_BYTES (((NR_CPUS * 7) > PAGE_SIZE) ? NR_CPUS * 7= : PAGE_SIZE) + #endif /* __LINUX_CPUMASK_H */ --=20 2.31.1