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
20 static 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 */
61 int 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
67 static 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 */
89 int 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 }
94 EXPORT_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 */
105 int 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 }
110 EXPORT_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 */
121 void 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 */
143 void 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 }
154 EXPORT_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 */
166 int 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
194 out:
195 kernfs_put(kn);
196 return result;
197 }
198 EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);
199
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