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 9420EC433EF for ; Fri, 15 Jul 2022 13:58:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232699AbiGON6S (ORCPT ); Fri, 15 Jul 2022 09:58:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55764 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229629AbiGON6D (ORCPT ); Fri, 15 Jul 2022 09:58:03 -0400 Received: from mail-oi1-x22b.google.com (mail-oi1-x22b.google.com [IPv6:2607:f8b0:4864:20::22b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F8AC820E2; Fri, 15 Jul 2022 06:58:02 -0700 (PDT) Received: by mail-oi1-x22b.google.com with SMTP id i126so6160797oih.4; Fri, 15 Jul 2022 06:58:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=pWWv1KjyLTxceoIzSgy/J2oEMl6lFWv01sP88AzTVPo=; b=hy6A+q4WFgzT0FtJwgri6Gva45SKUhbqrX+TC2oEBddixiPv7wdKlHSAdBnQfupc/7 Yym9Wmt4saQj9DK2MkwAcJlZe2T5h/5+gIwPQuJVrDoovWg6VOL6poCmKkxNncp1DKtM YUJfJyRdi2d0GUlIxB5OM/snsNXqsKyV4qT457NjwNvvtfs3ZEPbAP+rWeusaFogisiq nQtMgMi6937mFeZeOmXXb5gCKdjeOhrYq9owTM7sRuy9SZG40VuITyrep7+Fn0D/gj/e cHJWJ/2AgI1nYOgQK5nDxJs4c9LhMy638pIAk+Ult+MszOYmb79700XjDWA6dFBG73+x 9Geg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=pWWv1KjyLTxceoIzSgy/J2oEMl6lFWv01sP88AzTVPo=; b=YElVnnbXS6W9FY9mbeRMVdW+plQNRdtPKLMm3SPYU1ozqk9vXt1nqn8+4hozq6EXoH 8ZF9r21QOyK61vYfi246/IzfJyuEN3HdGXiBZ8xDTTsl84irH9WTH5dqflkxAh/YxU56 +Vq4C3ifQ0DEztAx4ErtVgAvFlRE95XUuxGTP+JUSqLoocL51HSt+WHFQkKpO/1HxiNd X5adxu+dJ0yUiTnsgdLec5KKOUNSNJtYMqhJzITplw0v3uxxD2W9aZF70G8zU6idhhci siDsyOfYLQsgyvmQCAAiMEs0wcsI/zSr9lEBLkopKFvo4HBdqmjc9uHpp9JbDnj/wmlw 5xxw== X-Gm-Message-State: AJIora/3A8X9aSnRGx0IGrJCVlXURYZJJpzrmkyBM8VOKCUderSTP+Jc XIDJ3KGcYIlQu3utbydv9Fk= X-Google-Smtp-Source: AGRyM1sDdKwE/nzapTw7FtXptc62bmMajKWpwknjCsW6on5LO+kQEKuNpxWGAUWKzgoFtLOAEDAIKA== X-Received: by 2002:aca:43d5:0:b0:339:e447:fe2f with SMTP id q204-20020aca43d5000000b00339e447fe2fmr10220246oia.113.1657893481311; Fri, 15 Jul 2022 06:58:01 -0700 (PDT) Received: from localhost ([12.97.180.36]) by smtp.gmail.com with ESMTPSA id er10-20020a056870c88a00b0010cbd1baf5esm2261951oab.51.2022.07.15.06.58.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Jul 2022 06:58:01 -0700 (PDT) Date: Fri, 15 Jul 2022 06:58:00 -0700 From: Yury Norov To: Phil Auld Cc: linux-kernel@vger.kernel.org, Greg Kroah-Hartman , "Rafael J . Wysocki" , Barry Song <21cnbao@gmail.com>, Tian Tao , stable@vger.kernel.org Subject: Re: [PATCH v5] drivers/base: fix userspace break from using bin_attributes for cpumap and cpulist Message-ID: References: <20220715134924.3466194-1-pauld@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220715134924.3466194-1-pauld@redhat.com> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Fri, Jul 15, 2022 at 09:49:24AM -0400, Phil Auld wrote: > 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 == 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 = 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 size limitation of cpumap ABI") > Fixes: bb9ec13d156 ("topology: use bin_attribute to break the size limitation 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, struct kobject *kobj, > return n; > } > > -static BIN_ATTR_RO(cpumap, 0); > +static BIN_ATTR_RO(cpumap, CPUMAP_FILE_MAX_BYTES); > > 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, struct kobject *kobj, > return n; > } > > -static BIN_ATTR_RO(cpulist, 0); > +static BIN_ATTR_RO(cpulist, CPULIST_FILE_MAX_BYTES); > > /** > * 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); > > 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); > > 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); > > 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); > > #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 > > #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 > > 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); > > #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 > > #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 > > static struct bin_attribute *bin_attrs[] = { > 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 cpumask *mask, > [0] = 1UL \ > } } > > +/* > + * Provide a valid theoretical max size for cpumap and cpulist sysfs files > + * to avoid breaking userspace which may allocate a buffer based on the size > + * 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 */ > -- > 2.31.1