net: create reusable function for getting ownership info of sysfs inodes

Make net_ns_get_ownership() reusable by networking code outside of core.
This is useful, for example, to allow bridge related sysfs files to be
owned by container root.

Add a function comment since this is a potentially dangerous function to
use given the way that kobject_get_ownership() works by initializing uid
and gid before calling .get_ownership().

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index a71264d75d7f..9b5fdc50519a 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -10,6 +10,7 @@
 #include <linux/workqueue.h>
 #include <linux/list.h>
 #include <linux/sysctl.h>
+#include <linux/uidgid.h>
 
 #include <net/flow.h>
 #include <net/netns/core.h>
@@ -170,6 +171,8 @@ extern struct net init_net;
 struct net *copy_net_ns(unsigned long flags, struct user_namespace *user_ns,
 			struct net *old_net);
 
+void net_ns_get_ownership(const struct net *net, kuid_t *uid, kgid_t *gid);
+
 void net_ns_barrier(void);
 #else /* CONFIG_NET_NS */
 #include <linux/sched.h>
@@ -182,6 +185,13 @@ static inline struct net *copy_net_ns(unsigned long flags,
 	return old_net;
 }
 
+static inline void net_ns_get_ownership(const struct net *net,
+					kuid_t *uid, kgid_t *gid)
+{
+	*uid = GLOBAL_ROOT_UID;
+	*gid = GLOBAL_ROOT_GID;
+}
+
 static inline void net_ns_barrier(void) {}
 #endif /* CONFIG_NET_NS */