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, 4 insertions, 4 deletions

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index d7bec49ee9ea..80de5e98a66d 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -264,14 +264,14 @@ void ipx_unregister_sysctl(void);
 #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)
 {
@@ -309,7 +309,7 @@ static inline int check_net(const 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