1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/sysfs/symlink.c - sysfs symlink 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#include <linux/fs.h>
13#include <linux/module.h>
14#include <linux/kobject.h>
15#include <linux/mutex.h>
16#include <linux/security.h>
17
18#include "sysfs.h"
19
20static int sysfs_do_create_link_sd(struct kernfs_node *parent,
21				   struct kobject *target_kobj,
22				   const char *name, int warn)
23{
24	struct kernfs_node *kn, *target = NULL;
25
26	if (WARN_ON(!name || !parent))
27		return -EINVAL;
28
29	/*
30	 * We don't own @target_kobj and it may be removed at any time.
31	 * Synchronize using sysfs_symlink_target_lock.  See
32	 * sysfs_remove_dir() for details.
33	 */
34	spin_lock(&sysfs_symlink_target_lock);
35	if (target_kobj->sd) {
36		target = target_kobj->sd;
37		kernfs_get(target);
38	}
39	spin_unlock(&sysfs_symlink_target_lock);
40
41	if (!target)
42		return -ENOENT;
43
44	kn = kernfs_create_link(parent, name, target);
45	kernfs_put(target);
46
47	if (!IS_ERR(kn))
48		return 0;
49
50	if (warn && PTR_ERR(kn) == -EEXIST)
51		sysfs_warn_dup(parent, name);
52	return PTR_ERR(kn);
53}
54
55/**
56 *	sysfs_create_link_sd - create symlink to a given object.
57 *	@kn:		directory we're creating the link in.
58 *	@target:	object we're pointing to.
59 *	@name:		name of the symlink.
60 */
61int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
62			 const char *name)
63{
64	return sysfs_do_create_link_sd(kn, target, name, 1);
65}
66
67static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
68				const char *name, int warn)
69{
70	struct kernfs_node *parent = NULL;
71
72	if (!kobj)
73		parent = sysfs_root_kn;
74	else
75		parent = kobj->sd;
76
77	if (!parent)
78		return -EFAULT;
79
80	return sysfs_do_create_link_sd(parent, target, name, warn);
81}
82
83/**
84 *	sysfs_create_link - create symlink between two objects.
85 *	@kobj:	object whose directory we're creating the link in.
86 *	@target:	object we're pointing to.
87 *	@name:		name of the symlink.
88 */
89int sysfs_create_link(struct kobject *kobj, struct kobject *target,
90		      const char *name)
91{
92	return sysfs_do_create_link(kobj, target, name, 1);
93}
94EXPORT_SYMBOL_GPL(sysfs_create_link);
95
96/**
97 *	sysfs_create_link_nowarn - create symlink between two objects.
98 *	@kobj:	object whose directory we're creating the link in.
99 *	@target:	object we're pointing to.
100 *	@name:		name of the symlink.
101 *
102 *	This function does the same as sysfs_create_link(), but it
103 *	doesn't warn if the link already exists.
104 */
105int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
106			     const char *name)
107{
108	return sysfs_do_create_link(kobj, target, name, 0);
109}
110EXPORT_SYMBOL_GPL(sysfs_create_link_nowarn);
111
112/**
113 *	sysfs_delete_link - remove symlink in object's directory.
114 *	@kobj:	object we're acting for.
115 *	@targ:	object we're pointing to.
116 *	@name:	name of the symlink to remove.
117 *
118 *	Unlike sysfs_remove_link sysfs_delete_link has enough information
119 *	to successfully delete symlinks in tagged directories.
120 */
121void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
122			const char *name)
123{
124	const void *ns = NULL;
125
126	/*
127	 * We don't own @target and it may be removed at any time.
128	 * Synchronize using sysfs_symlink_target_lock.  See
129	 * sysfs_remove_dir() for details.
130	 */
131	spin_lock(&sysfs_symlink_target_lock);
132	if (targ->sd && kernfs_ns_enabled(kobj->sd))
133		ns = targ->sd->ns;
134	spin_unlock(&sysfs_symlink_target_lock);
135	kernfs_remove_by_name_ns(kobj->sd, name, ns);
136}
137
138/**
139 *	sysfs_remove_link - remove symlink in object's directory.
140 *	@kobj:	object we're acting for.
141 *	@name:	name of the symlink to remove.
142 */
143void sysfs_remove_link(struct kobject *kobj, const char *name)
144{
145	struct kernfs_node *parent = NULL;
146
147	if (!kobj)
148		parent = sysfs_root_kn;
149	else
150		parent = kobj->sd;
151
152	kernfs_remove_by_name(parent, name);
153}
154EXPORT_SYMBOL_GPL(sysfs_remove_link);
155
156/**
157 *	sysfs_rename_link_ns - rename symlink in object's directory.
158 *	@kobj:	object we're acting for.
159 *	@targ:	object we're pointing to.
160 *	@old:	previous name of the symlink.
161 *	@new:	new name of the symlink.
162 *	@new_ns: new namespace of the symlink.
163 *
164 *	A helper function for the common rename symlink idiom.
165 */
166int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
167			 const char *old, const char *new, const void *new_ns)
168{
169	struct kernfs_node *parent, *kn = NULL;
170	const void *old_ns = NULL;
171	int result;
172
173	if (!kobj)
174		parent = sysfs_root_kn;
175	else
176		parent = kobj->sd;
177
178	if (targ->sd)
179		old_ns = targ->sd->ns;
180
181	result = -ENOENT;
182	kn = kernfs_find_and_get_ns(parent, old, old_ns);
183	if (!kn)
184		goto out;
185
186	result = -EINVAL;
187	if (kernfs_type(kn) != KERNFS_LINK)
188		goto out;
189	if (kn->symlink.target_kn->priv != targ)
190		goto out;
191
192	result = kernfs_rename_ns(kn, parent, new, new_ns);
193
194out:
195	kernfs_put(kn);
196	return result;
197}
198EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);
199