kernfs: pass struct ns_common instead of const void * for namespace tags

kernfs has historically used const void * to pass around namespace tags
used for directory-level namespace filtering. The only current user of
this is sysfs network namespace tagging where struct net pointers are
cast to void *.

Replace all const void * namespace parameters with const struct
ns_common * throughout the kernfs, sysfs, and kobject namespace layers.
This includes the kobj_ns_type_operations callbacks, kobject_namespace(),
and all sysfs/kernfs APIs that accept or return namespace tags.

Passing struct ns_common is needed because various codepaths require
access to the underlying namespace. A struct ns_common can always be
converted back to the concrete namespace type (e.g., struct net) via
container_of() or to_ns_common() in the reverse direction.

This is a preparatory change for switching to ns_id-based directory
iteration to prevent a KASLR pointer leak through the current use of
raw namespace pointers as hash seeds and comparison keys.

Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/include/linux/device/class.h b/include/linux/device/class.h
index 65880e60c720..021da0d61796 100644
--- a/include/linux/device/class.h
+++ b/include/linux/device/class.h
@@ -62,7 +62,7 @@ struct class {
 	int (*shutdown_pre)(struct device *dev);
 
 	const struct kobj_ns_type_operations *ns_type;
-	const void *(*namespace)(const struct device *dev);
+	const struct ns_common *(*namespace)(const struct device *dev);
 
 	void (*get_ownership)(const struct device *dev, kuid_t *uid, kgid_t *gid);
 
@@ -180,9 +180,9 @@ struct class_attribute {
 	struct class_attribute class_attr_##_name = __ATTR_WO(_name)
 
 int __must_check class_create_file_ns(const struct class *class, const struct class_attribute *attr,
-				      const void *ns);
+				      const struct ns_common *ns);
 void class_remove_file_ns(const struct class *class, const struct class_attribute *attr,
-			  const void *ns);
+			  const struct ns_common *ns);
 
 static inline int __must_check class_create_file(const struct class *class,
 						 const struct class_attribute *attr)