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 <[e-mail]>

drivers/base/class.c

···
 };
 
 int class_create_file_ns(const struct class *cls, const struct class_attribute *attr,
-			 const void *ns)
+			 const struct ns_common *ns)
 {
 	struct subsys_private *sp = class_to_subsys(cls);
 	int error;
···
 EXPORT_SYMBOL_GPL(class_create_file_ns);
 
 void class_remove_file_ns(const struct class *cls, const struct class_attribute *attr,
-			  const void *ns)
+			  const struct ns_common *ns)
 {
 	struct subsys_private *sp = class_to_subsys(cls);
 

drivers/base/core.c

···
 	kfree(p);
 }
 
-static const void *device_namespace(const struct kobject *kobj)
+static const struct ns_common *device_namespace(const struct kobject *kobj)
 {
 	const struct device *dev = kobj_to_dev(kobj);
-	const void *ns = NULL;
 
 	if (dev->class && dev->class->namespace)
-		ns = dev->class->namespace(dev);
+		return dev->class->namespace(dev);
 
-	return ns;
+	return NULL;
 }
 
 static void device_get_ownership(const struct kobject *kobj, kuid_t *uid, kgid_t *gid)

drivers/infiniband/core/device.c

···
 	return 0;
 }
 
-static const void *net_namespace(const struct device *d)
+static const struct ns_common *net_namespace(const struct device *d)
 {
 	const struct ib_core_device *coredev =
 			container_of(d, struct ib_core_device, dev);
+	struct net *net = read_pnet(&coredev->rdma_net);
 
-	return read_pnet(&coredev->rdma_net);
+	return net ? to_ns_common(net) : NULL;
 }
 
 static struct class ib_class = {

drivers/infiniband/ulp/srp/ib_srp.c

···
 #include <linux/jiffies.h>
 #include <linux/lockdep.h>
 #include <linux/inet.h>
+#include <net/net_namespace.h>
 #include <rdma/ib_cache.h>
 
 #include <linux/atomic.h>
···
 	scsi_remove_host(target->scsi_host);
 	srp_stop_rport_timers(target->rport);
 	srp_disconnect_target(target);
-	kobj_ns_drop(KOBJ_NS_TYPE_NET, target->net);
+	kobj_ns_drop(KOBJ_NS_TYPE_NET, to_ns_common(target->net));
 	for (i = 0; i < target->ch_count; i++) {
 		ch = &target->ch[i];
 		srp_free_ch_ib(target, ch);
···
 
 	target = host_to_target(target_host);
 
-	target->net		= kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+	target->net		= to_net_ns(kobj_ns_grab_current(KOBJ_NS_TYPE_NET));
 	target->io_class	= SRP_REV16A_IB_IO_CLASS;
 	target->scsi_host	= target_host;
 	target->srp_host	= host;
···
 		 * earlier in this function.
 		 */
 		if (target->state != SRP_TARGET_REMOVED)
-			kobj_ns_drop(KOBJ_NS_TYPE_NET, target->net);
+			kobj_ns_drop(KOBJ_NS_TYPE_NET, to_ns_common(target->net));
 		scsi_host_put(target->scsi_host);
 	}
 

drivers/net/bonding/bond_sysfs.c

···
 	sysfs_attr_init(&bn->class_attr_bonding_masters.attr);
 
 	ret = netdev_class_create_file_ns(&bn->class_attr_bonding_masters,
-					  bn->net);
+					  to_ns_common(bn->net));
 	/* Permit multiple loads of the module by ignoring failures to
 	 * create the bonding_masters sysfs file.  Bonding devices
 	 * created by second or subsequent loads of the module will
···
 /* Remove /sys/class/net/bonding_masters. */
 void __net_exit bond_destroy_sysfs(struct bond_net *bn)
 {
-	netdev_class_remove_file_ns(&bn->class_attr_bonding_masters, bn->net);
+	netdev_class_remove_file_ns(&bn->class_attr_bonding_masters, to_ns_common(bn->net));
 }
 
 /* Initialize sysfs for each bond.  This sets up and registers

drivers/net/ipvlan/ipvtap.c

···
 static dev_t ipvtap_major;
 static struct cdev ipvtap_cdev;
 
-static const void *ipvtap_net_namespace(const struct device *d)
+static const struct ns_common *ipvtap_net_namespace(const struct device *d)
 {
 	const struct net_device *dev = to_net_dev(d->parent);
-	return dev_net(dev);
+
+	return to_ns_common(dev_net(dev));
 }
 
 static struct class ipvtap_class = {

drivers/net/macvtap.c

···
  */
 static dev_t macvtap_major;
 
-static const void *macvtap_net_namespace(const struct device *d)
+static const struct ns_common *macvtap_net_namespace(const struct device *d)
 {
 	const struct net_device *dev = to_net_dev(d->parent);
-	return dev_net(dev);
+
+	return to_ns_common(dev_net(dev));
 }
 
 static struct class macvtap_class = {

fs/kernfs/dir.c

···
  *
  *	Return: 31-bit hash of ns + name (so it fits in an off_t)
  */
-static unsigned int kernfs_name_hash(const char *name, const void *ns)
+static unsigned int kernfs_name_hash(const char *name,
+				     const struct ns_common *ns)
 {
 	unsigned long hash = init_name_hash(ns);
 	unsigned int len = strlen(name);
···
 }
 
 static int kernfs_name_compare(unsigned int hash, const char *name,
-			       const void *ns, const struct kernfs_node *kn)
+			       const struct ns_common *ns, const struct kernfs_node *kn)
 {
 	if (hash < kn->hash)
 		return -1;
···
  */
 static struct kernfs_node *kernfs_find_ns(struct kernfs_node *parent,
 					  const unsigned char *name,
-					  const void *ns)
+					  const struct ns_common *ns)
 {
 	struct rb_node *node = parent->dir.children.rb_node;
 	bool has_ns = kernfs_ns_enabled(parent);
···
 
 static struct kernfs_node *kernfs_walk_ns(struct kernfs_node *parent,
 					  const unsigned char *path,
-					  const void *ns)
+					  const struct ns_common *ns)
 {
 	ssize_t len;
 	char *p, *name;
···
  * Return: pointer to the found kernfs_node on success, %NULL on failure.
  */
 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
-					   const char *name, const void *ns)
+					   const char *name,
+					   const struct ns_common *ns)
 {
 	struct kernfs_node *kn;
 	struct kernfs_root *root = kernfs_root(parent);
···
  * Return: pointer to the found kernfs_node on success, %NULL on failure.
  */
 struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
-					   const char *path, const void *ns)
+					   const char *path,
+					   const struct ns_common *ns)
 {
 	struct kernfs_node *kn;
 	struct kernfs_root *root = kernfs_root(parent);
···
 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 					 const char *name, umode_t mode,
 					 kuid_t uid, kgid_t gid,
-					 void *priv, const void *ns)
+					 void *priv,
+					 const struct ns_common *ns)
 {
 	struct kernfs_node *kn;
 	int rc;
···
 	struct kernfs_node *kn;
 	struct kernfs_root *root;
 	struct inode *inode = NULL;
-	const void *ns = NULL;
+	const struct ns_common *ns = NULL;
 
 	root = kernfs_root(parent);
 	down_read(&root->kernfs_rwsem);
···
  * Return: %0 on success, -ENOENT if such entry doesn't exist.
  */
 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
-			     const void *ns)
+			     const struct ns_common *ns)
 {
 	struct kernfs_node *kn;
 	struct kernfs_root *root;
···
  * Return: %0 on success, -errno on failure.
  */
 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
-		     const char *new_name, const void *new_ns)
+		     const char *new_name, const struct ns_common *new_ns)
 {
 	struct kernfs_node *old_parent;
 	struct kernfs_root *root;
···
 	return 0;
 }
 
-static struct kernfs_node *kernfs_dir_pos(const void *ns,
+static struct kernfs_node *kernfs_dir_pos(const struct ns_common *ns,
 	struct kernfs_node *parent, loff_t hash, struct kernfs_node *pos)
 {
 	if (pos) {
···
 	return pos;
 }
 
-static struct kernfs_node *kernfs_dir_next_pos(const void *ns,
+static struct kernfs_node *kernfs_dir_next_pos(const struct ns_common *ns,
 	struct kernfs_node *parent, ino_t ino, struct kernfs_node *pos)
 {
 	pos = kernfs_dir_pos(ns, parent, ino, pos);
···
 	struct kernfs_node *parent = kernfs_dentry_node(dentry);
 	struct kernfs_node *pos = file->private_data;
 	struct kernfs_root *root;
-	const void *ns = NULL;
+	const struct ns_common *ns = NULL;
 
 	if (!dir_emit_dots(file, ctx))
 		return 0;

fs/kernfs/file.c

···
 					 umode_t mode, kuid_t uid, kgid_t gid,
 					 loff_t size,
 					 const struct kernfs_ops *ops,
-					 void *priv, const void *ns,
+					 void *priv, const struct ns_common *ns,
 					 struct lock_class_key *key)
 {
 	struct kernfs_node *kn;

fs/kernfs/kernfs-internal.h

···
 	 * instance.  If multiple tags become necessary, make the following
 	 * an array and compare kernfs_node tag against every entry.
 	 */
-	const void		*ns;
+	const struct ns_common	*ns;
 
 	/* anchored at kernfs_root->supers, protected by kernfs_rwsem */
 	struct list_head	node;

fs/kernfs/mount.c

···
  *
  * Return: the namespace tag associated with kernfs super_block @sb.
  */
-const void *kernfs_super_ns(struct super_block *sb)
+const struct ns_common *kernfs_super_ns(struct super_block *sb)
 {
 	struct kernfs_super_info *info = kernfs_info(sb);
 

fs/nfs/sysfs.c

···
 #include <linux/netdevice.h>
 #include <linux/string.h>
 #include <linux/nfs_fs.h>
+#include <net/net_namespace.h>
 #include <linux/rcupdate.h>
 #include <linux/lockd/lockd.h>
 
···
 	kfree(rcu_dereference_raw(c->identifier));
 }
 
-static const void *nfs_netns_client_namespace(const struct kobject *kobj)
+static const struct ns_common *nfs_netns_client_namespace(const struct kobject *kobj)
 {
-	return container_of(kobj, struct nfs_netns_client, kobject)->net;
+	return to_ns_common(container_of(kobj, struct nfs_netns_client,
+					 kobject)->net);
 }
 
 static struct kobj_attribute nfs_netns_client_id = __ATTR(identifier,
···
 	kfree(c);
 }
 
-static const void *nfs_netns_namespace(const struct kobject *kobj)
+static const struct ns_common *nfs_netns_namespace(const struct kobject *kobj)
 {
-	return container_of(kobj, struct nfs_netns_client, nfs_net_kobj)->net;
+	return to_ns_common(container_of(kobj, struct nfs_netns_client,
+					 nfs_net_kobj)->net);
 }
 
 static struct kobj_type nfs_netns_object_type = {
···
 	/* no-op: why? see lib/kobject.c kobject_cleanup() */
 }
 
-static const void *nfs_netns_server_namespace(const struct kobject *kobj)
+static const struct ns_common *nfs_netns_server_namespace(const struct kobject *kobj)
 {
-	return container_of(kobj, struct nfs_server, kobj)->nfs_client->cl_net;
+	return to_ns_common(container_of(kobj, struct nfs_server,
+					 kobj)->nfs_client->cl_net);
 }
 
 static struct kobj_type nfs_sb_ktype = {

fs/sysfs/dir.c

···
  * @kobj: object we're creating directory for
  * @ns: the namespace tag to use
  */
-int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
+int sysfs_create_dir_ns(struct kobject *kobj, const struct ns_common *ns)
 {
 	struct kernfs_node *parent, *kn;
 	kuid_t uid;
···
 }
 
 int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
-			const void *new_ns)
+			const struct ns_common *new_ns)
 {
 	struct kernfs_node *parent;
 	int ret;
···
 }
 
 int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
-		      const void *new_ns)
+		      const struct ns_common *new_ns)
 {
 	struct kernfs_node *kn = kobj->sd;
 	struct kernfs_node *new_parent;

fs/sysfs/file.c

···
 
 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
 		const struct attribute *attr, umode_t mode, kuid_t uid,
-		kgid_t gid, const void *ns)
+		kgid_t gid, const struct ns_common *ns)
 {
 	struct kobject *kobj = parent->priv;
 	const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
···
 
 int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
 		const struct bin_attribute *battr, umode_t mode, size_t size,
-		kuid_t uid, kgid_t gid, const void *ns)
+		kuid_t uid, kgid_t gid, const struct ns_common *ns)
 {
 	const struct attribute *attr = &battr->attr;
 	struct lock_class_key *key = NULL;
···
  * @ns: namespace the new file should belong to
  */
 int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
-			 const void *ns)
+			 const struct ns_common *ns)
 {
 	kuid_t uid;
 	kgid_t gid;
···
  * Hash the attribute name and namespace tag and kill the victim.
  */
 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
-			  const void *ns)
+			  const struct ns_common *ns)
 {
 	struct kernfs_node *parent = kobj->sd;
 

fs/sysfs/mount.c

···
 static int sysfs_init_fs_context(struct fs_context *fc)
 {
 	struct kernfs_fs_context *kfc;
-	struct net *netns;
+	struct ns_common *ns;
 
 	if (!(fc->sb_flags & SB_KERNMOUNT)) {
 		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
···
 	if (!kfc)
 		return -ENOMEM;
 
-	kfc->ns_tag = netns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+	kfc->ns_tag = ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
 	kfc->root = sysfs_root;
 	kfc->magic = SYSFS_MAGIC;
 	fc->fs_private = kfc;
 	fc->ops = &sysfs_fs_context_ops;
-	if (netns) {
+	if (ns) {
+		struct net *netns = to_net_ns(ns);
+
 		put_user_ns(fc->user_ns);
 		fc->user_ns = get_user_ns(netns->user_ns);
 	}
···
 
 static void sysfs_kill_sb(struct super_block *sb)
 {
-	void *ns = (void *)kernfs_super_ns(sb);
+	struct ns_common *ns = (struct ns_common *)kernfs_super_ns(sb);
 
 	kernfs_kill_sb(sb);
 	kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);

fs/sysfs/symlink.c

···
 void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
 			const char *name)
 {
-	const void *ns = NULL;
+	const struct ns_common *ns = NULL;
 
 	/*
 	 * We don't own @target and it may be removed at any time.
···
  *	A helper function for the common rename symlink idiom.
  */
 int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
-			 const char *old, const char *new, const void *new_ns)
+			 const char *old, const char *new,
+			 const struct ns_common *new_ns)
 {
 	struct kernfs_node *parent, *kn = NULL;
-	const void *old_ns = NULL;
+	const struct ns_common *old_ns = NULL;
 	int result;
 
 	if (!kobj)

fs/sysfs/sysfs.h

···
  */
 int sysfs_add_file_mode_ns(struct kernfs_node *parent,
 		const struct attribute *attr, umode_t amode, kuid_t uid,
-		kgid_t gid, const void *ns);
+		kgid_t gid, const struct ns_common *ns);
 int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
 		const struct bin_attribute *battr, umode_t mode, size_t size,
-		kuid_t uid, kgid_t gid, const void *ns);
+		kuid_t uid, kgid_t gid, const struct ns_common *ns);
 
 /*
  * symlink.c

include/linux/device/class.h

···
 	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);
 
···
 	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)

include/linux/kernfs.h

···
 struct file;
 struct dentry;
 struct iattr;
+struct ns_common;
 struct seq_file;
 struct vm_area_struct;
 struct vm_operations_struct;
···
 
 	struct rb_node		rb;
 
-	const void		*ns;	/* namespace tag */
+	const struct ns_common	*ns;	/* namespace tag */
 	unsigned int		hash;	/* ns + name hash */
 	unsigned short		flags;
 	umode_t			mode;
···
  */
 struct kernfs_fs_context {
 	struct kernfs_root	*root;		/* Root of the hierarchy being mounted */
-	void			*ns_tag;	/* Namespace tag of the mount (or NULL) */
+	struct ns_common	*ns_tag;	/* Namespace tag of the mount (or NULL) */
 	unsigned long		magic;		/* File system specific magic number */
 
 	/* The following are set/used by kernfs_mount() */
···
 void pr_cont_kernfs_path(struct kernfs_node *kn);
 struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
 struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
-					   const char *name, const void *ns);
+					   const char *name,
+					   const struct ns_common *ns);
 struct kernfs_node *kernfs_walk_and_get_ns(struct kernfs_node *parent,
-					   const char *path, const void *ns);
+					   const char *path,
+					   const struct ns_common *ns);
 void kernfs_get(struct kernfs_node *kn);
 void kernfs_put(struct kernfs_node *kn);
 
···
 struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
 					 const char *name, umode_t mode,
 					 kuid_t uid, kgid_t gid,
-					 void *priv, const void *ns);
+					 void *priv,
+					 const struct ns_common *ns);
 struct kernfs_node *kernfs_create_empty_dir(struct kernfs_node *parent,
 					    const char *name);
 struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
···
 					 kuid_t uid, kgid_t gid,
 					 loff_t size,
 					 const struct kernfs_ops *ops,
-					 void *priv, const void *ns,
+					 void *priv,
+					 const struct ns_common *ns,
 					 struct lock_class_key *key);
 struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
 				       const char *name,
···
 void kernfs_unbreak_active_protection(struct kernfs_node *kn);
 bool kernfs_remove_self(struct kernfs_node *kn);
 int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
-			     const void *ns);
+			     const struct ns_common *ns);
 int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
-		     const char *new_name, const void *new_ns);
+		     const char *new_name, const struct ns_common *new_ns);
 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
 __poll_t kernfs_generic_poll(struct kernfs_open_file *of,
 			     struct poll_table_struct *pt);
···
 int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
 		     const void *value, size_t size, int flags);
 
-const void *kernfs_super_ns(struct super_block *sb);
+const struct ns_common *kernfs_super_ns(struct super_block *sb);
 int kernfs_get_tree(struct fs_context *fc);
 void kernfs_free_fs_context(struct fs_context *fc);
 void kernfs_kill_sb(struct super_block *sb);
···
 
 static inline struct kernfs_node *
 kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
-		       const void *ns)
+		       const struct ns_common *ns)
 { return NULL; }
 static inline struct kernfs_node *
 kernfs_walk_and_get_ns(struct kernfs_node *parent, const char *path,
-		       const void *ns)
+		       const struct ns_common *ns)
 { return NULL; }
 
 static inline void kernfs_get(struct kernfs_node *kn) { }
···
 static inline struct kernfs_node *
 kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
 		     umode_t mode, kuid_t uid, kgid_t gid,
-		     void *priv, const void *ns)
+		     void *priv, const struct ns_common *ns)
 { return ERR_PTR(-ENOSYS); }
 
 static inline struct kernfs_node *
 __kernfs_create_file(struct kernfs_node *parent, const char *name,
 		     umode_t mode, kuid_t uid, kgid_t gid,
 		     loff_t size, const struct kernfs_ops *ops,
-		     void *priv, const void *ns, struct lock_class_key *key)
+		     void *priv, const struct ns_common *ns,
+		     struct lock_class_key *key)
 { return ERR_PTR(-ENOSYS); }
 
 static inline struct kernfs_node *
···
 { return false; }
 
 static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
-					   const char *name, const void *ns)
+					   const char *name,
+					   const struct ns_common *ns)
 { return -ENOSYS; }
 
 static inline int kernfs_rename_ns(struct kernfs_node *kn,
 				   struct kernfs_node *new_parent,
-				   const char *new_name, const void *new_ns)
+				   const char *new_name,
+				   const struct ns_common *new_ns)
 { return -ENOSYS; }
 
 static inline int kernfs_setattr(struct kernfs_node *kn,
···
 				   const void *value, size_t size, int flags)
 { return -ENOSYS; }
 
-static inline const void *kernfs_super_ns(struct super_block *sb)
+static inline const struct ns_common *kernfs_super_ns(struct super_block *sb)
 { return NULL; }
 
 static inline int kernfs_get_tree(struct fs_context *fc)

include/linux/kobject.h

···
 struct kobject * __must_check kobject_get_unless_zero(struct kobject *kobj);
 void kobject_put(struct kobject *kobj);
 
-const void *kobject_namespace(const struct kobject *kobj);
+const struct ns_common *kobject_namespace(const struct kobject *kobj);
 void kobject_get_ownership(const struct kobject *kobj, kuid_t *uid, kgid_t *gid);
 char *kobject_get_path(const struct kobject *kobj, gfp_t flag);
 
···
 	const struct sysfs_ops *sysfs_ops;
 	const struct attribute_group **default_groups;
 	const struct kobj_ns_type_operations *(*child_ns_type)(const struct kobject *kobj);
-	const void *(*namespace)(const struct kobject *kobj);
+	const struct ns_common *(*namespace)(const struct kobject *kobj);
 	void (*get_ownership)(const struct kobject *kobj, kuid_t *uid, kgid_t *gid);
 };
 

include/linux/kobject_ns.h

···
 #ifndef _LINUX_KOBJECT_NS_H
 #define _LINUX_KOBJECT_NS_H
 
+struct ns_common;
 struct sock;
 struct kobject;
 
···
 struct kobj_ns_type_operations {
 	enum kobj_ns_type type;
 	bool (*current_may_mount)(void);
-	void *(*grab_current_ns)(void);
-	const void *(*netlink_ns)(struct sock *sk);
-	const void *(*initial_ns)(void);
-	void (*drop_ns)(void *);
+	struct ns_common *(*grab_current_ns)(void);
+	const struct ns_common *(*netlink_ns)(struct sock *sk);
+	const struct ns_common *(*initial_ns)(void);
+	void (*drop_ns)(struct ns_common *);
 };
 
 int kobj_ns_type_register(const struct kobj_ns_type_operations *ops);
···
 const struct kobj_ns_type_operations *kobj_ns_ops(const struct kobject *kobj);
 
 bool kobj_ns_current_may_mount(enum kobj_ns_type type);
-void *kobj_ns_grab_current(enum kobj_ns_type type);
-void kobj_ns_drop(enum kobj_ns_type type, void *ns);
+struct ns_common *kobj_ns_grab_current(enum kobj_ns_type type);
+void kobj_ns_drop(enum kobj_ns_type type, struct ns_common *ns);
 
 #endif /* _LINUX_KOBJECT_NS_H */

include/linux/netdevice.h

···
 }
 
 int netdev_class_create_file_ns(const struct class_attribute *class_attr,
-				const void *ns);
+				const struct ns_common *ns);
 void netdev_class_remove_file_ns(const struct class_attribute *class_attr,
-				 const void *ns);
+				 const struct ns_common *ns);
 
 extern const struct kobj_ns_type_operations net_ns_type_operations;
 

include/linux/sysfs.h

···
 
 #ifdef CONFIG_SYSFS
 
-int __must_check sysfs_create_dir_ns(struct kobject *kobj, const void *ns);
+int __must_check sysfs_create_dir_ns(struct kobject *kobj, const struct ns_common *ns);
 void sysfs_remove_dir(struct kobject *kobj);
 int __must_check sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
-				     const void *new_ns);
+				     const struct ns_common *new_ns);
 int __must_check sysfs_move_dir_ns(struct kobject *kobj,
 				   struct kobject *new_parent_kobj,
-				   const void *new_ns);
+				   const struct ns_common *new_ns);
 int __must_check sysfs_create_mount_point(struct kobject *parent_kobj,
 					  const char *name);
 void sysfs_remove_mount_point(struct kobject *parent_kobj,
···
 
 int __must_check sysfs_create_file_ns(struct kobject *kobj,
 				      const struct attribute *attr,
-				      const void *ns);
+				      const struct ns_common *ns);
 int __must_check sysfs_create_files(struct kobject *kobj,
 				   const struct attribute * const *attr);
 int __must_check sysfs_chmod_file(struct kobject *kobj,
···
 						  const struct attribute *attr);
 void sysfs_unbreak_active_protection(struct kernfs_node *kn);
 void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
-			  const void *ns);
+			  const struct ns_common *ns);
 bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr);
 void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *attr);
 
···
 
 int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *target,
 			 const char *old_name, const char *new_name,
-			 const void *new_ns);
+			 const struct ns_common *new_ns);
 
 void sysfs_delete_link(struct kobject *dir, struct kobject *targ,
 			const char *name);
···
 
 #else /* CONFIG_SYSFS */
 
-static inline int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
+static inline int sysfs_create_dir_ns(struct kobject *kobj, const struct ns_common *ns)
 {
 	return 0;
 }
···
 }
 
 static inline int sysfs_rename_dir_ns(struct kobject *kobj,
-				      const char *new_name, const void *new_ns)
+				      const char *new_name, const struct ns_common *new_ns)
 {
 	return 0;
 }
 
 static inline int sysfs_move_dir_ns(struct kobject *kobj,
 				    struct kobject *new_parent_kobj,
-				    const void *new_ns)
+				    const struct ns_common *new_ns)
 {
 	return 0;
 }
···
 
 static inline int sysfs_create_file_ns(struct kobject *kobj,
 				       const struct attribute *attr,
-				       const void *ns)
+				       const struct ns_common *ns)
 {
 	return 0;
 }
···
 
 static inline void sysfs_remove_file_ns(struct kobject *kobj,
 					const struct attribute *attr,
-					const void *ns)
+					const struct ns_common *ns)
 {
 }
 
···
 
 static inline int sysfs_rename_link_ns(struct kobject *k, struct kobject *t,
 				       const char *old_name,
-				       const char *new_name, const void *ns)
+				       const char *new_name, const struct ns_common *ns)
 {
 	return 0;
 }

include/net/net_namespace.h

···
 #define ipx_unregister_sysctl()
 #endif
 
-#ifdef CONFIG_NET_NS
-void __put_net(struct net *net);
-
 static inline struct net *to_net_ns(struct ns_common *ns)
 {
 	return container_of(ns, struct net, ns);
 }
+
+#ifdef CONFIG_NET_NS
+void __put_net(struct net *net);
 
 /* Try using get_net_track() instead */
 static inline struct net *get_net(struct net *net)
···
 	return ns_ref_read(net) != 0;
 }
 
-void net_drop_ns(void *);
+void net_drop_ns(struct ns_common *);
 void net_passive_dec(struct net *net);
 
 #else

lib/kobject.c

···
  * and thus @kobj should have a namespace tag associated with it.  Returns
  * %NULL otherwise.
  */
-const void *kobject_namespace(const struct kobject *kobj)
+const struct ns_common *kobject_namespace(const struct kobject *kobj)
 {
 	const struct kobj_ns_type_operations *ns_ops = kobj_ns_ops(kobj);
 
···
 	return may_mount;
 }
 
-void *kobj_ns_grab_current(enum kobj_ns_type type)
+struct ns_common *kobj_ns_grab_current(enum kobj_ns_type type)
 {
-	void *ns = NULL;
+	struct ns_common *ns = NULL;
 
 	spin_lock(&kobj_ns_type_lock);
 	if (kobj_ns_type_is_valid(type) && kobj_ns_ops_tbl[type])
···
 }
 EXPORT_SYMBOL_GPL(kobj_ns_grab_current);
 
-void kobj_ns_drop(enum kobj_ns_type type, void *ns)
+void kobj_ns_drop(enum kobj_ns_type type, struct ns_common *ns)
 {
 	spin_lock(&kobj_ns_type_lock);
 	if (kobj_ns_type_is_valid(type) &&

lib/kobject_uevent.c

···
 
 	ops = kobj_ns_ops(kobj);
 	if (ops) {
-		const void *init_ns, *ns;
+		const struct ns_common *init_ns, *ns;
 
 		ns = kobj->ktype->namespace(kobj);
 		init_ns = ops->initial_ns();
···
 
 #ifdef CONFIG_NET
 	const struct kobj_ns_type_operations *ops;
-	const struct net *net = NULL;
+	const struct ns_common *ns = NULL;
 
 	ops = kobj_ns_ops(kobj);
 	if (!ops && kobj->kset) {
···
 	 */
 	if (ops && ops->netlink_ns && kobj->ktype->namespace)
 		if (ops->type == KOBJ_NS_TYPE_NET)
-			net = kobj->ktype->namespace(kobj);
+			ns = kobj->ktype->namespace(kobj);
 
-	if (!net)
+	if (!ns)
 		ret = uevent_net_broadcast_untagged(env, action_string,
 						    devpath);
-	else
+	else {
+		const struct net *net = container_of(ns, struct net, ns);
+
 		ret = uevent_net_broadcast_tagged(net->uevent_sock->sk, env,
 						  action_string, devpath);
+	}
 #endif
 
 	return ret;

net/core/net-sysfs.c

···
 	netdev_put(queue->dev, &queue->dev_tracker);
 }
 
-static const void *rx_queue_namespace(const struct kobject *kobj)
+static const struct ns_common *rx_queue_namespace(const struct kobject *kobj)
 {
 	struct netdev_rx_queue *queue = to_rx_queue(kobj);
 	struct device *dev = &queue->dev->dev;
-	const void *ns = NULL;
 
 	if (dev->class && dev->class->namespace)
-		ns = dev->class->namespace(dev);
+		return dev->class->namespace(dev);
 
-	return ns;
+	return NULL;
 }
 
 static void rx_queue_get_ownership(const struct kobject *kobj,
 				   kuid_t *uid, kgid_t *gid)
 {
-	const struct net *net = rx_queue_namespace(kobj);
+	const struct ns_common *ns = rx_queue_namespace(kobj);
 
-	net_ns_get_ownership(net, uid, gid);
+	net_ns_get_ownership(ns ? container_of(ns, struct net, ns) : NULL,
+			     uid, gid);
 }
 
 static const struct kobj_type rx_queue_ktype = {
···
 	netdev_put(queue->dev, &queue->dev_tracker);
 }
 
-static const void *netdev_queue_namespace(const struct kobject *kobj)
+static const struct ns_common *netdev_queue_namespace(const struct kobject *kobj)
 {
 	struct netdev_queue *queue = to_netdev_queue(kobj);
 	struct device *dev = &queue->dev->dev;
-	const void *ns = NULL;
 
 	if (dev->class && dev->class->namespace)
-		ns = dev->class->namespace(dev);
+		return dev->class->namespace(dev);
 
-	return ns;
+	return NULL;
 }
 
 static void netdev_queue_get_ownership(const struct kobject *kobj,
 				       kuid_t *uid, kgid_t *gid)
 {
-	const struct net *net = netdev_queue_namespace(kobj);
+	const struct ns_common *ns = netdev_queue_namespace(kobj);
 
-	net_ns_get_ownership(net, uid, gid);
+	net_ns_get_ownership(ns ? container_of(ns, struct net, ns) : NULL,
+			     uid, gid);
 }
 
 static const struct kobj_type netdev_queue_ktype = {
···
 	return ns_capable(net->user_ns, CAP_SYS_ADMIN);
 }
 
-static void *net_grab_current_ns(void)
+static struct ns_common *net_grab_current_ns(void)
 {
-	struct net *ns = current->nsproxy->net_ns;
+	struct net *net = current->nsproxy->net_ns;
 #ifdef CONFIG_NET_NS
-	if (ns)
-		refcount_inc(&ns->passive);
+	if (net)
+		refcount_inc(&net->passive);
 #endif
-	return ns;
+	return net ? to_ns_common(net) : NULL;
 }
 
-static const void *net_initial_ns(void)
+static const struct ns_common *net_initial_ns(void)
 {
-	return &init_net;
+	return to_ns_common(&init_net);
 }
 
-static const void *net_netlink_ns(struct sock *sk)
+static const struct ns_common *net_netlink_ns(struct sock *sk)
 {
-	return sock_net(sk);
+	return to_ns_common(sock_net(sk));
 }
 
 const struct kobj_ns_type_operations net_ns_type_operations = {
···
 	kvfree(dev);
 }
 
-static const void *net_namespace(const struct device *d)
+static const struct ns_common *net_namespace(const struct device *d)
 {
 	const struct net_device *dev = to_net_dev(d);
 
-	return dev_net(dev);
+	return to_ns_common(dev_net(dev));
 }
 
 static void net_get_ownership(const struct device *d, kuid_t *uid, kgid_t *gid)
···
 }
 
 int netdev_class_create_file_ns(const struct class_attribute *class_attr,
-				const void *ns)
+				const struct ns_common *ns)
 {
 	return class_create_file_ns(&net_class, class_attr, ns);
 }
 EXPORT_SYMBOL(netdev_class_create_file_ns);
 
 void netdev_class_remove_file_ns(const struct class_attribute *class_attr,
-				 const void *ns)
+				 const struct ns_common *ns)
 {
 	class_remove_file_ns(&net_class, class_attr, ns);
 }

net/core/net_namespace.c

···
 	}
 }
 
-void net_drop_ns(void *p)
+void net_drop_ns(struct ns_common *ns)
 {
-	struct net *net = (struct net *)p;
-
-	if (net)
-		net_passive_dec(net);
+	if (ns)
+		net_passive_dec(to_net_ns(ns));
 }
 
 struct net *copy_net_ns(u64 flags,

net/sunrpc/sysfs.c

···
 #include <linux/kobject.h>
 #include <linux/sunrpc/addr.h>
 #include <linux/sunrpc/xprtsock.h>
+#include <net/net_namespace.h>
 
 #include "sysfs.h"
 
···
 	kfree(xprt);
 }
 
-static const void *rpc_sysfs_client_namespace(const struct kobject *kobj)
+static const struct ns_common *rpc_sysfs_client_namespace(const struct kobject *kobj)
 {
-	return container_of(kobj, struct rpc_sysfs_client, kobject)->net;
+	return to_ns_common(container_of(kobj, struct rpc_sysfs_client,
+					 kobject)->net);
 }
 
-static const void *rpc_sysfs_xprt_switch_namespace(const struct kobject *kobj)
+static const struct ns_common *rpc_sysfs_xprt_switch_namespace(const struct kobject *kobj)
 {
-	return container_of(kobj, struct rpc_sysfs_xprt_switch, kobject)->net;
+	return to_ns_common(container_of(kobj, struct rpc_sysfs_xprt_switch,
+					 kobject)->net);
 }
 
-static const void *rpc_sysfs_xprt_namespace(const struct kobject *kobj)
+static const struct ns_common *rpc_sysfs_xprt_namespace(const struct kobject *kobj)
 {
-	return container_of(kobj, struct rpc_sysfs_xprt,
-			    kobject)->xprt->xprt_net;
+	return to_ns_common(container_of(kobj, struct rpc_sysfs_xprt,
+					 kobject)->xprt->xprt_net);
 }
 
 static struct kobj_attribute rpc_sysfs_clnt_version = __ATTR(rpc_version,

net/wireless/sysfs.c

···
 #define WIPHY_PM_OPS NULL
 #endif
 
-static const void *wiphy_namespace(const struct device *d)
+static const struct ns_common *wiphy_namespace(const struct device *d)
 {
 	struct wiphy *wiphy = container_of(d, struct wiphy, dev);
 
-	return wiphy_net(wiphy);
+	return to_ns_common(wiphy_net(wiphy));
 }
 
 struct class ieee80211_class = {