nsfs: generalize ns_get_path() for path resolution with a task

ns_get_path() takes struct task_struct and proc_ns_ops as its parameters. For path resolution directly from a namespace, e.g. based on a networking device's net name space, we need more flexibility. Add a ns_get_path_cb() helper which will allow callers to use any method of obtaining the name space reference. Convert ns_get_path() to use ns_get_path_cb(). Following patches will bring a networking user. CC: Eric W. Biederman <[email protected]> Suggested-by: Daniel Borkmann <[email protected]> Signed-off-by: Jakub Kicinski <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]>
mengdonglin · Dec 31, 2017 · cdab6ba · cdab6ba
1 parent ad8ad79
commit cdab6ba
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Showing 2 changed files with 29 additions and 3 deletions.
diff --git a/fs/nsfs.c b/fs/nsfs.c
@@ -103,14 +103,14 @@ static void *__ns_get_path(struct path *path, struct ns_common *ns)
 	goto got_it;
 }
 
-void *ns_get_path(struct path *path, struct task_struct *task,
-			const struct proc_ns_operations *ns_ops)
+void *ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb,
+		     void *private_data)
 {
 	struct ns_common *ns;
 	void *ret;
 
 again:
-	ns = ns_ops->get(task);
+	ns = ns_get_cb(private_data);
 	if (!ns)
 		return ERR_PTR(-ENOENT);
 
@@ -120,6 +120,29 @@ void *ns_get_path(struct path *path, struct task_struct *task,
 	return ret;
 }
 
+struct ns_get_path_task_args {
+	const struct proc_ns_operations *ns_ops;
+	struct task_struct *task;
+};
+
+static struct ns_common *ns_get_path_task(void *private_data)
+{
+	struct ns_get_path_task_args *args = private_data;
+
+	return args->ns_ops->get(args->task);
+}
+
+void *ns_get_path(struct path *path, struct task_struct *task,
+		  const struct proc_ns_operations *ns_ops)
+{
+	struct ns_get_path_task_args args = {
+		.ns_ops	= ns_ops,
+		.task	= task,
+	};
+
+	return ns_get_path_cb(path, ns_get_path_task, &args);
+}
+
 int open_related_ns(struct ns_common *ns,
 		   struct ns_common *(*get_ns)(struct ns_common *ns))
 {

diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
@@ -78,6 +78,9 @@ extern struct file *proc_ns_fget(int fd);
 #define get_proc_ns(inode) ((struct ns_common *)(inode)->i_private)
 extern void *ns_get_path(struct path *path, struct task_struct *task,
 			const struct proc_ns_operations *ns_ops);
+typedef struct ns_common *ns_get_path_helper_t(void *);
+extern void *ns_get_path_cb(struct path *path, ns_get_path_helper_t ns_get_cb,
+			    void *private_data);
 
 extern int ns_get_name(char *buf, size_t size, struct task_struct *task,
 			const struct proc_ns_operations *ns_ops);