1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/sysfs/dir.c - sysfs core and dir operation implementation
4 *
5 * Copyright (c) 2001-3 Patrick Mochel
6 * Copyright (c) 2007 SUSE Linux Products GmbH
7 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
8 *
9 * Please see Documentation/filesystems/sysfs.rst for more information.
10 */
11
12#define pr_fmt(fmt)	"sysfs: " fmt
13
14#include <linux/fs.h>
15#include <linux/kobject.h>
16#include <linux/slab.h>
17#include "sysfs.h"
18
19DEFINE_SPINLOCK(sysfs_symlink_target_lock);
20
21void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
22{
23	char *buf;
24
25	buf = kzalloc(PATH_MAX, GFP_KERNEL);
26	if (buf)
27		kernfs_path(parent, buf, PATH_MAX);
28
29	pr_warn("cannot create duplicate filename '%s/%s'\n", buf, name);
30	dump_stack();
31
32	kfree(buf);
33}
34
35/**
36 * sysfs_create_dir_ns - create a directory for an object with a namespace tag
37 * @kobj: object we're creating directory for
38 * @ns: the namespace tag to use
39 */
40int sysfs_create_dir_ns(struct kobject *kobj, const void *ns)
41{
42	struct kernfs_node *parent, *kn;
43	kuid_t uid;
44	kgid_t gid;
45
46	if (WARN_ON(!kobj))
47		return -EINVAL;
48
49	if (kobj->parent)
50		parent = kobj->parent->sd;
51	else
52		parent = sysfs_root_kn;
53
54	if (!parent)
55		return -ENOENT;
56
57	kobject_get_ownership(kobj, &uid, &gid);
58
59	kn = kernfs_create_dir_ns(parent, kobject_name(kobj), 0755, uid, gid,
60				  kobj, ns);
61	if (IS_ERR(kn)) {
62		if (PTR_ERR(kn) == -EEXIST)
63			sysfs_warn_dup(parent, kobject_name(kobj));
64		return PTR_ERR(kn);
65	}
66
67	kobj->sd = kn;
68	return 0;
69}
70
71/**
72 *	sysfs_remove_dir - remove an object's directory.
73 *	@kobj:	object.
74 *
75 *	The only thing special about this is that we remove any files in
76 *	the directory before we remove the directory, and we've inlined
77 *	what used to be sysfs_rmdir() below, instead of calling separately.
78 */
79void sysfs_remove_dir(struct kobject *kobj)
80{
81	struct kernfs_node *kn = kobj->sd;
82
83	/*
84	 * In general, kobject owner is responsible for ensuring removal
85	 * doesn't race with other operations and sysfs doesn't provide any
86	 * protection; however, when @kobj is used as a symlink target, the
87	 * symlinking entity usually doesn't own @kobj and thus has no
88	 * control over removal.  @kobj->sd may be removed anytime
89	 * and symlink code may end up dereferencing an already freed node.
90	 *
91	 * sysfs_symlink_target_lock synchronizes @kobj->sd
92	 * disassociation against symlink operations so that symlink code
93	 * can safely dereference @kobj->sd.
94	 */
95	spin_lock(&sysfs_symlink_target_lock);
96	kobj->sd = NULL;
97	spin_unlock(&sysfs_symlink_target_lock);
98
99	if (kn) {
100		WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
101		kernfs_remove(kn);
102	}
103}
104
105int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
106			const void *new_ns)
107{
108	struct kernfs_node *parent;
109	int ret;
110
111	parent = kernfs_get_parent(kobj->sd);
112	ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
113	kernfs_put(parent);
114	return ret;
115}
116
117int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
118		      const void *new_ns)
119{
120	struct kernfs_node *kn = kobj->sd;
121	struct kernfs_node *new_parent;
122
123	new_parent = new_parent_kobj && new_parent_kobj->sd ?
124		new_parent_kobj->sd : sysfs_root_kn;
125
126	return kernfs_rename_ns(kn, new_parent, kn->name, new_ns);
127}
128
129/**
130 * sysfs_create_mount_point - create an always empty directory
131 * @parent_kobj:  kobject that will contain this always empty directory
132 * @name: The name of the always empty directory to add
133 */
134int sysfs_create_mount_point(struct kobject *parent_kobj, const char *name)
135{
136	struct kernfs_node *kn, *parent = parent_kobj->sd;
137
138	kn = kernfs_create_empty_dir(parent, name);
139	if (IS_ERR(kn)) {
140		if (PTR_ERR(kn) == -EEXIST)
141			sysfs_warn_dup(parent, name);
142		return PTR_ERR(kn);
143	}
144
145	return 0;
146}
147EXPORT_SYMBOL_GPL(sysfs_create_mount_point);
148
149/**
150 *	sysfs_remove_mount_point - remove an always empty directory.
151 *	@parent_kobj: kobject that will contain this always empty directory
152 *	@name: The name of the always empty directory to remove
153 *
154 */
155void sysfs_remove_mount_point(struct kobject *parent_kobj, const char *name)
156{
157	struct kernfs_node *parent = parent_kobj->sd;
158
159	kernfs_remove_by_name_ns(parent, name, NULL);
160}
161EXPORT_SYMBOL_GPL(sysfs_remove_mount_point);
162