kernfs: allow creating kernfs objects with arbitrary uid/gid

This change allows creating kernfs files and directories with arbitrary
uid/gid instead of always using GLOBAL_ROOT_UID/GID by extending
kernfs_create_dir_ns() and kernfs_create_file_ns() with uid/gid arguments.
The "simple" kernfs_create_file() and kernfs_create_dir() are left alone
and always create objects belonging to the global root.

When creating symlinks ownership (uid/gid) is taken from the target kernfs
object.

Co-Developed-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 6 insertions, 3 deletions

diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index 58eba92a0e41..e39b884f0867 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -52,7 +52,9 @@ int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
                 return -ENOENT;
 
         kn = kernfs_create_dir_ns(parent, kobject_name(kobj),
-                                  S_IRWXU | S_IRUGO | S_IXUGO, kobj, ns);
+                                  S_IRWXU | S_IRUGO | S_IXUGO,
+                                  GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+                                  kobj, ns);
         if (IS_ERR(kn)) {
                 if (PTR_ERR(kn) == -EEXIST)
                         sysfs_warn_dup(parent, kobject_name(kobj));
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 5c13f29bfcdb..513fa691ecbd 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -302,8 +302,9 @@ int sysfs_add_file_mode_ns(struct kernfs_node *parent,
         if (!attr->ignore_lockdep)
                 key = attr->key ?: (struct lock_class_key *)&attr->skey;
 #endif
-        kn = __kernfs_create_file(parent, attr->name, mode & 0777, size, ops,
-                                  (void *)attr, ns, key);
+        kn = __kernfs_create_file(parent, attr->name,
+                                  mode & 0777, GLOBAL_ROOT_UID, GLOBAL_ROOT_GID,
+                                  size, ops, (void *)attr, ns, key);
         if (IS_ERR(kn)) {
                 if (PTR_ERR(kn) == -EEXIST)
                         sysfs_warn_dup(parent, attr->name);