2 files changed, 276 insertions, 7 deletions

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 130fc6fbcc03..26bbf960e2a2 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -558,3 +558,151 @@ void sysfs_remove_bin_file(struct kobject *kobj,
 	kernfs_remove_by_name(kobj->sd, attr->attr.name);
 }
 EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
+
+static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
+				 kgid_t kgid)
+{
+	struct iattr newattrs = {
+		.ia_valid = ATTR_UID | ATTR_GID,
+		.ia_uid = kuid,
+		.ia_gid = kgid,
+	};
+	return kernfs_setattr(kn, &newattrs);
+}
+
+/**
+ *	sysfs_link_change_owner - change owner of a sysfs file.
+ *	@kobj:	object of the kernfs_node the symlink is located in.
+ *	@targ:	object of the kernfs_node the symlink points to.
+ *	@name:	name of the link.
+ *	@kuid:	new owner's kuid
+ *	@kgid:	new owner's kgid
+ *
+ * This function looks up the sysfs symlink entry @name under @kobj and changes
+ * the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
+ * @targ.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
+			    const char *name, kuid_t kuid, kgid_t kgid)
+{
+	struct kernfs_node *kn = NULL;
+	int error;
+
+	if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
+		return -EINVAL;
+
+	error = -ENOENT;
+	kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
+	if (!kn)
+		goto out;
+
+	error = -EINVAL;
+	if (kernfs_type(kn) != KERNFS_LINK)
+		goto out;
+	if (kn->symlink.target_kn->priv != targ)
+		goto out;
+
+	error = internal_change_owner(kn, kuid, kgid);
+
+out:
+	kernfs_put(kn);
+	return error;
+}
+
+/**
+ *	sysfs_file_change_owner - change owner of a sysfs file.
+ *	@kobj:	object.
+ *	@name:	name of the file to change.
+ *	@kuid:	new owner's kuid
+ *	@kgid:	new owner's kgid
+ *
+ * This function looks up the sysfs entry @name under @kobj and changes the
+ * ownership to @kuid/@kgid.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
+			    kgid_t kgid)
+{
+	struct kernfs_node *kn;
+	int error;
+
+	if (!name)
+		return -EINVAL;
+
+	if (!kobj->state_in_sysfs)
+		return -EINVAL;
+
+	kn = kernfs_find_and_get(kobj->sd, name);
+	if (!kn)
+		return -ENOENT;
+
+	error = internal_change_owner(kn, kuid, kgid);
+
+	kernfs_put(kn);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_file_change_owner);
+
+/**
+ *	sysfs_change_owner - change owner of the given object.
+ *	@kobj:	object.
+ *	@kuid:	new owner's kuid
+ *	@kgid:	new owner's kgid
+ *
+ * Change the owner of the default directory, files, groups, and attributes of
+ * @kobj to @kuid/@kgid. Note that sysfs_change_owner mirrors how the sysfs
+ * entries for a kobject are added by driver core. In summary,
+ * sysfs_change_owner() takes care of the default directory entry for @kobj,
+ * the default attributes associated with the ktype of @kobj and the default
+ * attributes associated with the ktype of @kobj.
+ * Additional properties not added by driver core have to be changed by the
+ * driver or subsystem which created them. This is similar to how
+ * driver/subsystem specific entries are removed.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
+{
+	int error;
+	const struct kobj_type *ktype;
+
+	if (!kobj->state_in_sysfs)
+		return -EINVAL;
+
+	/* Change the owner of the kobject itself. */
+	error = internal_change_owner(kobj->sd, kuid, kgid);
+	if (error)
+		return error;
+
+	ktype = get_ktype(kobj);
+	if (ktype) {
+		struct attribute **kattr;
+
+		/*
+		 * Change owner of the default attributes associated with the
+		 * ktype of @kobj.
+		 */
+		for (kattr = ktype->default_attrs; kattr && *kattr; kattr++) {
+			error = sysfs_file_change_owner(kobj, (*kattr)->name,
+							kuid, kgid);
+			if (error)
+				return error;
+		}
+
+		/*
+		 * Change owner of the default groups associated with the
+		 * ktype of @kobj.
+		 */
+		error = sysfs_groups_change_owner(kobj, ktype->default_groups,
+						  kuid, kgid);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(sysfs_change_owner);
diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
index c4ab045926b7..64e6a6698935 100644
--- a/fs/sysfs/group.c
+++ b/fs/sysfs/group.c
@@ -13,6 +13,7 @@
 #include <linux/dcache.h>
 #include <linux/namei.h>
 #include <linux/err.h>
+#include <linux/fs.h>
 #include "sysfs.h"
 
 
@@ -415,15 +416,18 @@ void sysfs_remove_link_from_group(struct kobject *kobj, const char *group_name,
 EXPORT_SYMBOL_GPL(sysfs_remove_link_from_group);
 
 /**
- * __compat_only_sysfs_link_entry_to_kobj - add a symlink to a kobject pointing
+ * compat_only_sysfs_link_entry_to_kobj - add a symlink to a kobject pointing
  * to a group or an attribute
  * @kobj:		The kobject containing the group.
  * @target_kobj:	The target kobject.
  * @target_name:	The name of the target group or attribute.
+ * @symlink_name:	The name of the symlink file (target_name will be
+ *			considered if symlink_name is NULL).
  */
-int __compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
-				      struct kobject *target_kobj,
-				      const char *target_name)
+int compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
+					 struct kobject *target_kobj,
+					 const char *target_name,
+					 const char *symlink_name)
 {
 	struct kernfs_node *target;
 	struct kernfs_node *entry;
@@ -448,12 +452,129 @@ int __compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
 		return -ENOENT;
 	}
 
-	link = kernfs_create_link(kobj->sd, target_name, entry);
+	if (!symlink_name)
+		symlink_name = target_name;
+
+	link = kernfs_create_link(kobj->sd, symlink_name, entry);
 	if (PTR_ERR(link) == -EEXIST)
-		sysfs_warn_dup(kobj->sd, target_name);
+		sysfs_warn_dup(kobj->sd, symlink_name);
 
 	kernfs_put(entry);
 	kernfs_put(target);
 	return PTR_ERR_OR_ZERO(link);
 }
-EXPORT_SYMBOL_GPL(__compat_only_sysfs_link_entry_to_kobj);
+EXPORT_SYMBOL_GPL(compat_only_sysfs_link_entry_to_kobj);
+
+static int sysfs_group_attrs_change_owner(struct kernfs_node *grp_kn,
+					  const struct attribute_group *grp,
+					  struct iattr *newattrs)
+{
+	struct kernfs_node *kn;
+	int error;
+
+	if (grp->attrs) {
+		struct attribute *const *attr;
+
+		for (attr = grp->attrs; *attr; attr++) {
+			kn = kernfs_find_and_get(grp_kn, (*attr)->name);
+			if (!kn)
+				return -ENOENT;
+
+			error = kernfs_setattr(kn, newattrs);
+			kernfs_put(kn);
+			if (error)
+				return error;
+		}
+	}
+
+	if (grp->bin_attrs) {
+		struct bin_attribute *const *bin_attr;
+
+		for (bin_attr = grp->bin_attrs; *bin_attr; bin_attr++) {
+			kn = kernfs_find_and_get(grp_kn, (*bin_attr)->attr.name);
+			if (!kn)
+				return -ENOENT;
+
+			error = kernfs_setattr(kn, newattrs);
+			kernfs_put(kn);
+			if (error)
+				return error;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * sysfs_group_change_owner - change owner of an attribute group.
+ * @kobj:	The kobject containing the group.
+ * @grp:	The attribute group.
+ * @kuid:	new owner's kuid
+ * @kgid:	new owner's kgid
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_group_change_owner(struct kobject *kobj,
+			     const struct attribute_group *grp, kuid_t kuid,
+			     kgid_t kgid)
+{
+	struct kernfs_node *grp_kn;
+	int error;
+	struct iattr newattrs = {
+		.ia_valid = ATTR_UID | ATTR_GID,
+		.ia_uid = kuid,
+		.ia_gid = kgid,
+	};
+
+	if (!kobj->state_in_sysfs)
+		return -EINVAL;
+
+	if (grp->name) {
+		grp_kn = kernfs_find_and_get(kobj->sd, grp->name);
+	} else {
+		kernfs_get(kobj->sd);
+		grp_kn = kobj->sd;
+	}
+	if (!grp_kn)
+		return -ENOENT;
+
+	error = kernfs_setattr(grp_kn, &newattrs);
+	if (!error)
+		error = sysfs_group_attrs_change_owner(grp_kn, grp, &newattrs);
+
+	kernfs_put(grp_kn);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_group_change_owner);
+
+/**
+ * sysfs_groups_change_owner - change owner of a set of attribute groups.
+ * @kobj:	The kobject containing the groups.
+ * @groups:	The attribute groups.
+ * @kuid:	new owner's kuid
+ * @kgid:	new owner's kgid
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_groups_change_owner(struct kobject *kobj,
+			      const struct attribute_group **groups,
+			      kuid_t kuid, kgid_t kgid)
+{
+	int error = 0, i;
+
+	if (!kobj->state_in_sysfs)
+		return -EINVAL;
+
+	if (!groups)
+		return 0;
+
+	for (i = 0; groups[i]; i++) {
+		error = sysfs_group_change_owner(kobj, groups[i], kuid, kgid);
+		if (error)
+			break;
+	}
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_groups_change_owner);