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From:   Tian Tao <tiantao6@hisilicon.com>
To:     <gregkh@linuxfoundation.org>, <rafael@kernel.org>,
        <andriy.shevchenko@linux.intel.com>, <akpm@linux-foundation.org>
CC:     <jonathan.cameron@huawei.com>, <song.bao.hua@hisilicon.com>,
        <linux-kernel@vger.kernel.org>, Tian Tao <tiantao6@hisilicon.com>
Subject: [PATCH v2 2/3] topology: use bin_attribute to avoid buff overflow
Date:   Wed, 2 Jun 2021 21:48:53 +0800
Message-ID: <1622641734-22538-3-git-send-email-tiantao6@hisilicon.com>
In-Reply-To: <1622641734-22538-1-git-send-email-tiantao6@hisilicon.com>
References: <1622641734-22538-1-git-send-email-tiantao6@hisilicon.com>
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Reading sys/devices/system/cpu/cpuX/topology/ returns cpu topology.
However, the size of this file is limited to PAGE_SIZE because of the
limitation for sysfs attribute. so we use bin_attribute instead of
attribute to avoid NR_CPUS too big to cause buff overflow.

This patch is based on the following discussion.
https://lore.kernel.org/lkml/20210319041618.14316-2-song.bao.hua@hisilicon.com/

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
---
 drivers/base/topology.c | 115 ++++++++++++++++++++++++++----------------------
 1 file changed, 63 insertions(+), 52 deletions(-)

diff --git a/drivers/base/topology.c b/drivers/base/topology.c
index 4d254fc..013edbb 100644
--- a/drivers/base/topology.c
+++ b/drivers/base/topology.c
@@ -21,25 +21,27 @@ static ssize_t name##_show(struct device *dev,				\
 	return sysfs_emit(buf, "%d\n", topology_##name(dev->id));	\
 }
 
-#define define_siblings_show_map(name, mask)				\
-static ssize_t name##_show(struct device *dev,				\
-			   struct device_attribute *attr, char *buf)	\
-{									\
-	return cpumap_print_to_pagebuf(false, buf, topology_##mask(dev->id));\
+#define define_siblings_read_func(name, mask)					\
+static ssize_t name##_read(struct file *file, struct kobject *kobj,		\
+				  struct bin_attribute *attr, char *buf,	\
+				  loff_t off, size_t count)			\
+{										\
+	struct device *dev = kobj_to_dev(kobj);                                 \
+										\
+	return cpumap_print_to_buf(false, buf, topology_##mask(dev->id),	\
+				   off, count);                                 \
+}										\
+										\
+static ssize_t name##_list_read(struct file *file, struct kobject *kobj,	\
+				  struct bin_attribute *attr, char *buf,	\
+				  loff_t off, size_t count)			\
+{										\
+	struct device *dev = kobj_to_dev(kobj);					\
+										\
+	return cpumap_print_to_buf(true, buf, topology_##mask(dev->id),		\
+				   off, count);					\
 }
 
-#define define_siblings_show_list(name, mask)				\
-static ssize_t name##_list_show(struct device *dev,			\
-				struct device_attribute *attr,		\
-				char *buf)				\
-{									\
-	return cpumap_print_to_pagebuf(true, buf, topology_##mask(dev->id));\
-}
-
-#define define_siblings_show_func(name, mask)	\
-	define_siblings_show_map(name, mask);	\
-	define_siblings_show_list(name, mask)
-
 define_id_show_func(physical_package_id);
 static DEVICE_ATTR_RO(physical_package_id);
 
@@ -49,71 +51,80 @@ static DEVICE_ATTR_RO(die_id);
 define_id_show_func(core_id);
 static DEVICE_ATTR_RO(core_id);
 
-define_siblings_show_func(thread_siblings, sibling_cpumask);
-static DEVICE_ATTR_RO(thread_siblings);
-static DEVICE_ATTR_RO(thread_siblings_list);
+define_siblings_read_func(thread_siblings, sibling_cpumask);
+static BIN_ATTR_RO(thread_siblings, 0);
+static BIN_ATTR_RO(thread_siblings_list, 0);
 
-define_siblings_show_func(core_cpus, sibling_cpumask);
-static DEVICE_ATTR_RO(core_cpus);
-static DEVICE_ATTR_RO(core_cpus_list);
+define_siblings_read_func(core_cpus, sibling_cpumask);
+static BIN_ATTR_RO(core_cpus, 0);
+static BIN_ATTR_RO(core_cpus_list, 0);
 
-define_siblings_show_func(core_siblings, core_cpumask);
-static DEVICE_ATTR_RO(core_siblings);
-static DEVICE_ATTR_RO(core_siblings_list);
+define_siblings_read_func(core_siblings, core_cpumask);
+static BIN_ATTR_RO(core_siblings, 0);
+static BIN_ATTR_RO(core_siblings_list, 0);
 
-define_siblings_show_func(die_cpus, die_cpumask);
-static DEVICE_ATTR_RO(die_cpus);
-static DEVICE_ATTR_RO(die_cpus_list);
+define_siblings_read_func(die_cpus, die_cpumask);
+static BIN_ATTR_RO(die_cpus, 0);
+static BIN_ATTR_RO(die_cpus_list, 0);
 
-define_siblings_show_func(package_cpus, core_cpumask);
-static DEVICE_ATTR_RO(package_cpus);
-static DEVICE_ATTR_RO(package_cpus_list);
+define_siblings_read_func(package_cpus, core_cpumask);
+static BIN_ATTR_RO(package_cpus, 0);
+static BIN_ATTR_RO(package_cpus_list, 0);
 
 #ifdef CONFIG_SCHED_BOOK
 define_id_show_func(book_id);
 static DEVICE_ATTR_RO(book_id);
-define_siblings_show_func(book_siblings, book_cpumask);
-static DEVICE_ATTR_RO(book_siblings);
-static DEVICE_ATTR_RO(book_siblings_list);
+define_siblings_read_func(book_siblings, book_cpumask);
+static BIN_ATTR_RO(book_siblings, 0);
+static BIN_ATTR_RO(book_siblings_list, 0);
 #endif
 
 #ifdef CONFIG_SCHED_DRAWER
 define_id_show_func(drawer_id);
 static DEVICE_ATTR_RO(drawer_id);
-define_siblings_show_func(drawer_siblings, drawer_cpumask);
-static DEVICE_ATTR_RO(drawer_siblings);
-static DEVICE_ATTR_RO(drawer_siblings_list);
+define_siblings_read_func(drawer_siblings, drawer_cpumask);
+static BIN_ATTR_RO(drawer_siblings, 0);
+static BIN_ATTR_RO(drawer_siblings_list, 0);
 #endif
 
+static struct bin_attribute *bin_attrs[] = {
+	&bin_attr_core_cpus,
+	&bin_attr_core_cpus_list,
+	&bin_attr_thread_siblings,
+	&bin_attr_thread_siblings_list,
+	&bin_attr_core_siblings,
+	&bin_attr_core_siblings_list,
+	&bin_attr_die_cpus,
+	&bin_attr_die_cpus_list,
+	&bin_attr_package_cpus,
+	&bin_attr_package_cpus_list,
+#ifdef CONFIG_SCHED_BOOK
+	&bin_attr_book_siblings,
+	&bin_attr_book_siblings_list,
+#endif
+#ifdef CONFIG_SCHED_DRAWER
+	&bin_attr_drawer_siblings,
+	&bin_attr_drawer_siblings_list,
+#endif
+	NULL,
+};
+
 static struct attribute *default_attrs[] = {
 	&dev_attr_physical_package_id.attr,
 	&dev_attr_die_id.attr,
 	&dev_attr_core_id.attr,
-	&dev_attr_thread_siblings.attr,
-	&dev_attr_thread_siblings_list.attr,
-	&dev_attr_core_cpus.attr,
-	&dev_attr_core_cpus_list.attr,
-	&dev_attr_core_siblings.attr,
-	&dev_attr_core_siblings_list.attr,
-	&dev_attr_die_cpus.attr,
-	&dev_attr_die_cpus_list.attr,
-	&dev_attr_package_cpus.attr,
-	&dev_attr_package_cpus_list.attr,
 #ifdef CONFIG_SCHED_BOOK
 	&dev_attr_book_id.attr,
-	&dev_attr_book_siblings.attr,
-	&dev_attr_book_siblings_list.attr,
 #endif
 #ifdef CONFIG_SCHED_DRAWER
 	&dev_attr_drawer_id.attr,
-	&dev_attr_drawer_siblings.attr,
-	&dev_attr_drawer_siblings_list.attr,
 #endif
 	NULL
 };
 
 static const struct attribute_group topology_attr_group = {
 	.attrs = default_attrs,
+	.bin_attrs = bin_attrs,
 	.name = "topology"
 };
 
-- 
2.7.4