[PATCH net v2 2/3] net: core: add netdev_class_has_file_ns() helper function

[Taehee Yoo <ap420073@gmail.com>]

This helper function is to check whether the class file "/sys/class/net/*"
is existing or not.
In the next patch, this helper function will be used.

Reported-by: syzbot+830c6dbfc71edc4f0b8f@syzkaller.appspotmail.com
Fixes: b76cdba9cdb2 ("[PATCH] bonding: add sysfs functionality to bonding (large)")
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
---

v1 -> v2:
 - use class_has_file_ns(), which is introduced by the first patch.

 include/linux/netdevice.h | 2 +-
 net/core/net-sysfs.c      | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 130a668049ab..a04c487c0975 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4555,7 +4555,7 @@ int netdev_class_create_file_ns(const struct class_attribute *class_attr,
 				const void *ns);
 void netdev_class_remove_file_ns(const struct class_attribute *class_attr,
 				 const void *ns);
-
+bool netdev_class_has_file_ns(const char *name, const void *ns);
 static inline int netdev_class_create_file(const struct class_attribute *class_attr)
 {
 	return netdev_class_create_file_ns(class_attr, NULL);
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index cf0215734ceb..8a20d658eff0 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -1914,6 +1914,12 @@ void netdev_class_remove_file_ns(const struct class_attribute *class_attr,
 }
 EXPORT_SYMBOL(netdev_class_remove_file_ns);
 
+bool netdev_class_has_file_ns(const char *name, const void *ns)
+{
+	return class_has_file_ns(&net_class, name, ns);
+}
+EXPORT_SYMBOL(netdev_class_has_file_ns);
+
 int __init netdev_kobject_init(void)
 {
 	kobj_ns_type_register(&net_ns_type_operations);
-- 
2.17.1