[PATCH net 1/3] class: add class_find_and_get_file_ns() helper function

From: Taehee Yoo
Date: Tue Mar 24 2020 - 08:31:03 EST


The new helper function is to find and get a class file.
This function is useful for checking whether the class file is existing
or not. This function will be used by networking stack to
check "/sys/class/net/*" file.

Reported-by: syzbot+830c6dbfc71edc4f0b8f@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: b76cdba9cdb2 ("[PATCH] bonding: add sysfs functionality to bonding (large)")
Signed-off-by: Taehee Yoo <ap420073@xxxxxxxxx>
---
drivers/base/class.c | 12 ++++++++++++
include/linux/device/class.h | 4 +++-
2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/base/class.c b/drivers/base/class.c
index bcd410e6d70a..dedf41f32f0d 100644
--- a/drivers/base/class.c
+++ b/drivers/base/class.c
@@ -105,6 +105,17 @@ void class_remove_file_ns(struct class *cls, const struct class_attribute *attr,
sysfs_remove_file_ns(&cls->p->subsys.kobj, &attr->attr, ns);
}

+struct kernfs_node *class_find_and_get_file_ns(struct class *cls,
+ const char *name,
+ const void *ns)
+{
+ struct kernfs_node *kn = NULL;
+
+ if (cls)
+ kn = kernfs_find_and_get_ns(cls->p->subsys.kobj.sd, name, ns);
+ return kn;
+}
+
static struct class *class_get(struct class *cls)
{
if (cls)
@@ -580,6 +591,7 @@ int __init classes_init(void)

EXPORT_SYMBOL_GPL(class_create_file_ns);
EXPORT_SYMBOL_GPL(class_remove_file_ns);
+EXPORT_SYMBOL_GPL(class_find_and_get_file_ns);
EXPORT_SYMBOL_GPL(class_unregister);
EXPORT_SYMBOL_GPL(class_destroy);

diff --git a/include/linux/device/class.h b/include/linux/device/class.h
index e8d470c457d1..230cf2ce6d3f 100644
--- a/include/linux/device/class.h
+++ b/include/linux/device/class.h
@@ -209,7 +209,9 @@ extern int __must_check class_create_file_ns(struct class *class,
extern void class_remove_file_ns(struct class *class,
const struct class_attribute *attr,
const void *ns);
-
+struct kernfs_node *class_find_and_get_file_ns(struct class *cls,
+ const char *name,
+ const void *ns);
static inline int __must_check class_create_file(struct class *class,
const struct class_attribute *attr)
{
--
2.17.1