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Subject[PATCH net-next v3 7/8] net: create reusable function for getting ownership info of sysfs inodes
Date
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>
---
include/net/net_namespace.h | 10 ++++++++++
net/core/net-sysfs.c | 18 ------------------
net/core/net_namespace.c | 28 ++++++++++++++++++++++++++++
3 files changed, 38 insertions(+), 18 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 */

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index ada065fc685e..0a95bcf64cdc 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -656,24 +656,6 @@ static const struct attribute_group wireless_group = {
#define net_class_groups NULL
#endif /* CONFIG_SYSFS */

-static void net_ns_get_ownership(const struct net *net,
- kuid_t *uid, kgid_t *gid)
-{
- if (net) {
- kuid_t ns_root_uid = make_kuid(net->user_ns, 0);
- kgid_t ns_root_gid = make_kgid(net->user_ns, 0);
-
- if (uid_valid(ns_root_uid))
- *uid = ns_root_uid;
-
- if (gid_valid(ns_root_gid))
- *gid = ns_root_gid;
- } else {
- *uid = GLOBAL_ROOT_UID;
- *gid = GLOBAL_ROOT_GID;
- }
-}
-
#ifdef CONFIG_SYSFS
#define to_rx_queue_attr(_attr) \
container_of(_attr, struct rx_queue_attribute, attr)
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index a11e03f920d3..738871af5efa 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -17,6 +17,7 @@
#include <linux/user_namespace.h>
#include <linux/net_namespace.h>
#include <linux/sched/task.h>
+#include <linux/uidgid.h>

#include <net/sock.h>
#include <net/netlink.h>
@@ -448,6 +449,33 @@ struct net *copy_net_ns(unsigned long flags,
return net;
}

+/**
+ * net_ns_get_ownership - get sysfs ownership data for @net
+ * @net: network namespace in question (can be NULL)
+ * @uid: kernel user ID for sysfs objects
+ * @gid: kernel group ID for sysfs objects
+ *
+ * Returns the uid/gid pair of root in the user namespace associated with the
+ * given network namespace.
+ */
+void net_ns_get_ownership(const struct net *net, kuid_t *uid, kgid_t *gid)
+{
+ if (net) {
+ kuid_t ns_root_uid = make_kuid(net->user_ns, 0);
+ kgid_t ns_root_gid = make_kgid(net->user_ns, 0);
+
+ if (uid_valid(ns_root_uid))
+ *uid = ns_root_uid;
+
+ if (gid_valid(ns_root_gid))
+ *gid = ns_root_gid;
+ } else {
+ *uid = GLOBAL_ROOT_UID;
+ *gid = GLOBAL_ROOT_GID;
+ }
+}
+EXPORT_SYMBOL_GPL(net_ns_get_ownership);
+
static void unhash_nsid(struct net *net, struct net *last)
{
struct net *tmp;
--
2.7.4
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