Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 638 insertions, 0 deletions

diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
new file mode 100644
index 000000000..4e1e4f18a
--- /dev/null
+++ b/fs/sysfs/group.c
@@ -0,0 +1,638 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs/sysfs/group.c - Operations for adding/removing multiple files at once.
+ *
+ * Copyright (c) 2003 Patrick Mochel
+ * Copyright (c) 2003 Open Source Development Lab
+ * Copyright (c) 2013 Greg Kroah-Hartman
+ * Copyright (c) 2013 The Linux Foundation
+ */
+
+#include <linux/kobject.h>
+#include <linux/module.h>
+#include <linux/dcache.h>
+#include <linux/namei.h>
+#include <linux/err.h>
+#include <linux/fs.h>
+#include "sysfs.h"
+
+
+static void remove_files(struct kernfs_node *parent,
+			 const struct attribute_group *grp)
+{
+	struct attribute *const *attr;
+	const struct bin_attribute *const *bin_attr;
+
+	if (grp->attrs)
+		for (attr = grp->attrs; *attr; attr++)
+			kernfs_remove_by_name(parent, (*attr)->name);
+	if (grp->bin_attrs)
+		for (bin_attr = grp->bin_attrs; *bin_attr; bin_attr++)
+			kernfs_remove_by_name(parent, (*bin_attr)->attr.name);
+}
+
+static umode_t __first_visible(const struct attribute_group *grp, struct kobject *kobj)
+{
+	if (grp->attrs && grp->attrs[0] && grp->is_visible)
+		return grp->is_visible(kobj, grp->attrs[0], 0);
+
+	if (grp->attrs && grp->attrs[0] && grp->is_visible_const)
+		return grp->is_visible_const(kobj, grp->attrs[0], 0);
+
+	if (grp->bin_attrs && grp->bin_attrs[0] && grp->is_bin_visible)
+		return grp->is_bin_visible(kobj, grp->bin_attrs[0], 0);
+
+	return 0;
+}
+
+static int create_files(struct kernfs_node *parent, struct kobject *kobj,
+			kuid_t uid, kgid_t gid,
+			const struct attribute_group *grp, int update)
+{
+	struct attribute *const *attr;
+	const struct bin_attribute *const *bin_attr;
+	int error = 0, i;
+
+	if (grp->attrs) {
+		for (i = 0, attr = grp->attrs; *attr && !error; i++, attr++) {
+			umode_t mode = (*attr)->mode;
+
+			/*
+			 * In update mode, we're changing the permissions or
+			 * visibility.  Do this by first removing then
+			 * re-adding (if required) the file.
+			 */
+			if (update)
+				kernfs_remove_by_name(parent, (*attr)->name);
+			if (grp->is_visible || grp->is_visible_const) {
+				if (grp->is_visible)
+					mode = grp->is_visible(kobj, *attr, i);
+				else
+					mode = grp->is_visible_const(kobj, *attr, i);
+				mode &= ~SYSFS_GROUP_INVISIBLE;
+				if (!mode)
+					continue;
+			}
+
+			WARN(mode & ~(SYSFS_PREALLOC | 0664),
+			     "Attribute %s: Invalid permissions 0%o\n",
+			     (*attr)->name, mode);
+
+			mode &= SYSFS_PREALLOC | 0664;
+			error = sysfs_add_file_mode_ns(parent, *attr, mode, uid,
+						       gid, NULL);
+			if (unlikely(error))
+				break;
+		}
+		if (error) {
+			remove_files(parent, grp);
+			goto exit;
+		}
+	}
+
+	if (grp->bin_attrs) {
+		for (i = 0, bin_attr = grp->bin_attrs; *bin_attr; i++, bin_attr++) {
+			umode_t mode = (*bin_attr)->attr.mode;
+			size_t size = (*bin_attr)->size;
+
+			if (update)
+				kernfs_remove_by_name(parent,
+						(*bin_attr)->attr.name);
+			if (grp->is_bin_visible) {
+				mode = grp->is_bin_visible(kobj, *bin_attr, i);
+				mode &= ~SYSFS_GROUP_INVISIBLE;
+				if (!mode)
+					continue;
+			}
+			if (grp->bin_size)
+				size = grp->bin_size(kobj, *bin_attr, i);
+
+			WARN(mode & ~(SYSFS_PREALLOC | 0664),
+			     "Attribute %s: Invalid permissions 0%o\n",
+			     (*bin_attr)->attr.name, mode);
+
+			mode &= SYSFS_PREALLOC | 0664;
+			error = sysfs_add_bin_file_mode_ns(parent, *bin_attr,
+							   mode, size, uid, gid,
+							   NULL);
+			if (error)
+				break;
+		}
+		if (error)
+			remove_files(parent, grp);
+	}
+exit:
+	return error;
+}
+
+
+static int internal_create_group(struct kobject *kobj, int update,
+				 const struct attribute_group *grp)
+{
+	struct kernfs_node *kn;
+	kuid_t uid;
+	kgid_t gid;
+	int error;
+
+	if (WARN_ON(!kobj || (!update && !kobj->sd)))
+		return -EINVAL;
+
+	/* Updates may happen before the object has been instantiated */
+	if (unlikely(update && !kobj->sd))
+		return -EINVAL;
+
+	if (!grp->attrs && !grp->bin_attrs) {
+		pr_debug("sysfs: (bin_)attrs not set by subsystem for group: %s/%s, skipping\n",
+			 kobj->name, grp->name ?: "");
+		return 0;
+	}
+
+	kobject_get_ownership(kobj, &uid, &gid);
+	if (grp->name) {
+		umode_t mode = __first_visible(grp, kobj);
+
+		if (mode & SYSFS_GROUP_INVISIBLE)
+			mode = 0;
+		else
+			mode = S_IRWXU | S_IRUGO | S_IXUGO;
+
+		if (update) {
+			kn = kernfs_find_and_get(kobj->sd, grp->name);
+			if (!kn) {
+				pr_debug("attr grp %s/%s not created yet\n",
+					 kobj->name, grp->name);
+				/* may have been invisible prior to this update */
+				update = 0;
+			} else if (!mode) {
+				sysfs_remove_group(kobj, grp);
+				kernfs_put(kn);
+				return 0;
+			}
+		}
+
+		if (!update) {
+			if (!mode)
+				return 0;
+			kn = kernfs_create_dir_ns(kobj->sd, grp->name, mode,
+						  uid, gid, kobj, NULL);
+			if (IS_ERR(kn)) {
+				if (PTR_ERR(kn) == -EEXIST)
+					sysfs_warn_dup(kobj->sd, grp->name);
+				return PTR_ERR(kn);
+			}
+		}
+	} else {
+		kn = kobj->sd;
+	}
+
+	kernfs_get(kn);
+	error = create_files(kn, kobj, uid, gid, grp, update);
+	if (error) {
+		if (grp->name && !update)
+			kernfs_remove(kn);
+	}
+	kernfs_put(kn);
+
+	if (grp->name && update)
+		kernfs_put(kn);
+
+	return error;
+}
+
+/**
+ * sysfs_create_group - given a directory kobject, create an attribute group
+ * @kobj:	The kobject to create the group on
+ * @grp:	The attribute group to create
+ *
+ * This function creates a group for the first time.  It will explicitly
+ * warn and error if any of the attribute files being created already exist.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_create_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	return internal_create_group(kobj, 0, grp);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_group);
+
+static int internal_create_groups(struct kobject *kobj, int update,
+				  const struct attribute_group *const *groups)
+{
+	int error = 0;
+	int i;
+
+	if (!groups)
+		return 0;
+
+	for (i = 0; groups[i]; i++) {
+		error = internal_create_group(kobj, update, groups[i]);
+		if (error) {
+			while (--i >= 0)
+				sysfs_remove_group(kobj, groups[i]);
+			break;
+		}
+	}
+	return error;
+}
+
+/**
+ * sysfs_create_groups - given a directory kobject, create a bunch of attribute groups
+ * @kobj:	The kobject to create the group on
+ * @groups:	The attribute groups to create, NULL terminated
+ *
+ * This function creates a bunch of attribute groups.  If an error occurs when
+ * creating a group, all previously created groups will be removed, unwinding
+ * everything back to the original state when this function was called.
+ * It will explicitly warn and error if any of the attribute files being
+ * created already exist.
+ *
+ * Returns 0 on success or error code from sysfs_create_group on failure.
+ */
+int sysfs_create_groups(struct kobject *kobj,
+			const struct attribute_group *const *groups)
+{
+	return internal_create_groups(kobj, 0, groups);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_groups);
+
+/**
+ * sysfs_update_groups - given a directory kobject, create a bunch of attribute groups
+ * @kobj:	The kobject to update the group on
+ * @groups:	The attribute groups to update, NULL terminated
+ *
+ * This function update a bunch of attribute groups.  If an error occurs when
+ * updating a group, all previously updated groups will be removed together
+ * with already existing (not updated) attributes.
+ *
+ * Returns 0 on success or error code from sysfs_update_group on failure.
+ */
+int sysfs_update_groups(struct kobject *kobj,
+			const struct attribute_group *const *groups)
+{
+	return internal_create_groups(kobj, 1, groups);
+}
+EXPORT_SYMBOL_GPL(sysfs_update_groups);
+
+/**
+ * sysfs_update_group - given a directory kobject, update an attribute group
+ * @kobj:	The kobject to update the group on
+ * @grp:	The attribute group to update
+ *
+ * This function updates an attribute group.  Unlike
+ * sysfs_create_group(), it will explicitly not warn or error if any
+ * of the attribute files being created already exist.  Furthermore,
+ * if the visibility of the files has changed through the is_visible()
+ * callback, it will update the permissions and add or remove the
+ * relevant files. Changing a group's name (subdirectory name under
+ * kobj's directory in sysfs) is not allowed.
+ *
+ * The primary use for this function is to call it after making a change
+ * that affects group visibility.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_update_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	return internal_create_group(kobj, 1, grp);
+}
+EXPORT_SYMBOL_GPL(sysfs_update_group);
+
+/**
+ * sysfs_remove_group: remove a group from a kobject
+ * @kobj:	kobject to remove the group from
+ * @grp:	group to remove
+ *
+ * This function removes a group of attributes from a kobject.  The attributes
+ * previously have to have been created for this group, otherwise it will fail.
+ */
+void sysfs_remove_group(struct kobject *kobj,
+			const struct attribute_group *grp)
+{
+	struct kernfs_node *parent = kobj->sd;
+	struct kernfs_node *kn;
+
+	if (grp->name) {
+		kn = kernfs_find_and_get(parent, grp->name);
+		if (!kn) {
+			pr_debug("sysfs group '%s' not found for kobject '%s'\n",
+				 grp->name, kobject_name(kobj));
+			return;
+		}
+	} else {
+		kn = parent;
+		kernfs_get(kn);
+	}
+
+	remove_files(kn, grp);
+	if (grp->name)
+		kernfs_remove(kn);
+
+	kernfs_put(kn);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_group);
+
+/**
+ * sysfs_remove_groups - remove a list of groups
+ *
+ * @kobj:	The kobject for the groups to be removed from
+ * @groups:	NULL terminated list of groups to be removed
+ *
+ * If groups is not NULL, remove the specified groups from the kobject.
+ */
+void sysfs_remove_groups(struct kobject *kobj,
+			 const struct attribute_group *const *groups)
+{
+	int i;
+
+	if (!groups)
+		return;
+	for (i = 0; groups[i]; i++)
+		sysfs_remove_group(kobj, groups[i]);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_groups);
+
+/**
+ * sysfs_merge_group - merge files into a pre-existing named attribute group.
+ * @kobj:	The kobject containing the group.
+ * @grp:	The files to create and the attribute group they belong to.
+ *
+ * This function returns an error if the group doesn't exist, the .name field is
+ * NULL or any of the files already exist in that group, in which case none of
+ * the new files are created.
+ */
+int sysfs_merge_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	struct kernfs_node *parent;
+	kuid_t uid;
+	kgid_t gid;
+	int error = 0;
+	struct attribute *const *attr;
+	int i;
+
+	parent = kernfs_find_and_get(kobj->sd, grp->name);
+	if (!parent)
+		return -ENOENT;
+
+	kobject_get_ownership(kobj, &uid, &gid);
+
+	for ((i = 0, attr = grp->attrs); *attr && !error; (++i, ++attr))
+		error = sysfs_add_file_mode_ns(parent, *attr, (*attr)->mode,
+					       uid, gid, NULL);
+	if (error) {
+		while (--i >= 0)
+			kernfs_remove_by_name(parent, (*--attr)->name);
+	}
+	kernfs_put(parent);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_merge_group);
+
+/**
+ * sysfs_unmerge_group - remove files from a pre-existing named attribute group.
+ * @kobj:	The kobject containing the group.
+ * @grp:	The files to remove and the attribute group they belong to.
+ */
+void sysfs_unmerge_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	struct kernfs_node *parent;
+	struct attribute *const *attr;
+
+	parent = kernfs_find_and_get(kobj->sd, grp->name);
+	if (parent) {
+		for (attr = grp->attrs; *attr; ++attr)
+			kernfs_remove_by_name(parent, (*attr)->name);
+		kernfs_put(parent);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_unmerge_group);
+
+/**
+ * sysfs_add_link_to_group - add a symlink to an attribute group.
+ * @kobj:	The kobject containing the group.
+ * @group_name:	The name of the group.
+ * @target:	The target kobject of the symlink to create.
+ * @link_name:	The name of the symlink to create.
+ */
+int sysfs_add_link_to_group(struct kobject *kobj, const char *group_name,
+			    struct kobject *target, const char *link_name)
+{
+	struct kernfs_node *parent;
+	int error = 0;
+
+	parent = kernfs_find_and_get(kobj->sd, group_name);
+	if (!parent)
+		return -ENOENT;
+
+	error = sysfs_create_link_sd(parent, target, link_name);
+	kernfs_put(parent);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_add_link_to_group);
+
+/**
+ * sysfs_remove_link_from_group - remove a symlink from an attribute group.
+ * @kobj:	The kobject containing the group.
+ * @group_name:	The name of the group.
+ * @link_name:	The name of the symlink to remove.
+ */
+void sysfs_remove_link_from_group(struct kobject *kobj, const char *group_name,
+				  const char *link_name)
+{
+	struct kernfs_node *parent;
+
+	parent = kernfs_find_and_get(kobj->sd, group_name);
+	if (parent) {
+		kernfs_remove_by_name(parent, link_name);
+		kernfs_put(parent);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_link_from_group);
+
+/**
+ * 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,
+					 const char *symlink_name)
+{
+	struct kernfs_node *target;
+	struct kernfs_node *entry;
+	struct kernfs_node *link;
+
+	/*
+	 * We don't own @target_kobj and it may be removed at any time.
+	 * Synchronize using sysfs_symlink_target_lock. See sysfs_remove_dir()
+	 * for details.
+	 */
+	spin_lock(&sysfs_symlink_target_lock);
+	target = target_kobj->sd;
+	if (target)
+		kernfs_get(target);
+	spin_unlock(&sysfs_symlink_target_lock);
+	if (!target)
+		return -ENOENT;
+
+	entry = kernfs_find_and_get(target, target_name);
+	if (!entry) {
+		kernfs_put(target);
+		return -ENOENT;
+	}
+
+	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, symlink_name);
+
+	kernfs_put(entry);
+	kernfs_put(target);
+	return PTR_ERR_OR_ZERO(link);
+}
+EXPORT_SYMBOL_GPL(compat_only_sysfs_link_entry_to_kobj);
+
+static int sysfs_group_attrs_change_owner(struct kobject *kobj,
+					  struct kernfs_node *grp_kn,
+					  const struct attribute_group *grp,
+					  struct iattr *newattrs)
+{
+	struct kernfs_node *kn;
+	int error, i;
+	umode_t mode;
+
+	if (grp->attrs) {
+		struct attribute *const *attr;
+
+		for (i = 0, attr = grp->attrs; *attr; i++, attr++) {
+			if (grp->is_visible || grp->is_visible_const) {
+				if (grp->is_visible)
+					mode = grp->is_visible(kobj, *attr, i);
+				else
+					mode = grp->is_visible_const(kobj, *attr, i);
+				if (mode & SYSFS_GROUP_INVISIBLE)
+					break;
+				if (!mode)
+					continue;
+			}
+			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) {
+		const struct bin_attribute *const *bin_attr;
+
+		for (i = 0, bin_attr = grp->bin_attrs; *bin_attr; i++, bin_attr++) {
+			if (grp->is_bin_visible) {
+				mode = grp->is_bin_visible(kobj, *bin_attr, i);
+				if (mode & SYSFS_GROUP_INVISIBLE)
+					break;
+				if (!mode)
+					continue;
+			}
+			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(kobj, 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 *const *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);