[PATCH v2 3/3] drivers/base/node.c: use bin_attribute to avoid buff overflow

From: Tian Tao
Date: Wed Jun 02 2021 - 09:49:15 EST


Reading sys/devices/system/cpu/cpuX/nodeX/ returns cpumap and cpulist.
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.

Signed-off-by: Tian Tao <tiantao6@xxxxxxxxxxxxx>
---
drivers/base/node.c | 52 ++++++++++++++++++++++++++++++++++------------------
1 file changed, 34 insertions(+), 18 deletions(-)

diff --git a/drivers/base/node.c b/drivers/base/node.c
index f449dbb..2659bb44 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -27,42 +27,45 @@ static struct bus_type node_subsys = {
};


-static ssize_t node_read_cpumap(struct device *dev, bool list, char *buf)
+static ssize_t node_read_cpumap(struct device *dev, bool list,
+ char *buf, loff_t off, size_t count)
{
ssize_t n;
cpumask_var_t mask;
struct node *node_dev = to_node(dev);

- /* 2008/04/07: buf currently PAGE_SIZE, need 9 chars per 32 bits. */
- BUILD_BUG_ON((NR_CPUS/32 * 9) > (PAGE_SIZE-1));
-
if (!alloc_cpumask_var(&mask, GFP_KERNEL))
return 0;

cpumask_and(mask, cpumask_of_node(node_dev->dev.id), cpu_online_mask);
- n = cpumap_print_to_pagebuf(list, buf, mask);
+ n = cpumap_print_to_buf(list, buf, mask, off, count);
free_cpumask_var(mask);

return n;
}

-static inline ssize_t cpumap_show(struct device *dev,
- struct device_attribute *attr,
- char *buf)
+static inline ssize_t cpumap_read(struct file *file, struct kobject *kobj,
+ struct bin_attribute *attr, char *buf,
+ loff_t off, size_t count)
{
- return node_read_cpumap(dev, false, buf);
+ struct device *dev = kobj_to_dev(kobj);
+
+ return node_read_cpumap(dev, false, buf, off, count);
}

-static DEVICE_ATTR_RO(cpumap);

-static inline ssize_t cpulist_show(struct device *dev,
- struct device_attribute *attr,
- char *buf)
+static BIN_ATTR_RO(cpumap, 0);
+
+static inline ssize_t cpulist_read(struct file *file, struct kobject *kobj,
+ struct bin_attribute *attr, char *buf,
+ loff_t off, size_t count)
{
- return node_read_cpumap(dev, true, buf);
+ struct device *dev = kobj_to_dev(kobj);
+
+ return node_read_cpumap(dev, true, buf, off, count);
}

-static DEVICE_ATTR_RO(cpulist);
+static BIN_ATTR_RO(cpulist, 0);

/**
* struct node_access_nodes - Access class device to hold user visible
@@ -557,15 +560,28 @@ static ssize_t node_read_distance(struct device *dev,
static DEVICE_ATTR(distance, 0444, node_read_distance, NULL);

static struct attribute *node_dev_attrs[] = {
- &dev_attr_cpumap.attr,
- &dev_attr_cpulist.attr,
&dev_attr_meminfo.attr,
&dev_attr_numastat.attr,
&dev_attr_distance.attr,
&dev_attr_vmstat.attr,
NULL
};
-ATTRIBUTE_GROUPS(node_dev);
+
+static struct bin_attribute *node_dev_bin_attrs[] = {
+ &bin_attr_cpumap,
+ &bin_attr_cpulist,
+ NULL,
+};
+
+static const struct attribute_group node_dev_group = {
+ .attrs = node_dev_attrs,
+ .bin_attrs = node_dev_bin_attrs
+};
+
+static const struct attribute_group *node_dev_groups[] = {
+ &node_dev_group,
+ NULL,
+};

#ifdef CONFIG_HUGETLBFS
/*
--
2.7.4